Vol. 20, No.2 Investigations • Service • Infonnation Summer 1990

Plate Tectonics and the Gulf ofCalifornia Region

by Nancy SchmidtArizona Geological Survey

_ Figure 1. Satellite photo of the northern Gulf of California region. C = Colorado Riverdelta;K= Kino Bay (Bah{aKino); P =Pinacatevolcanic field (Sierra Pinacate);R =RockyPoint (Puerto Penasco); S = Salton Sea; Y = Yuma. .

The Gulf of California, familiar to many Arizonans as a recrea­tionmecca and importantpartofMexico's fishing and touristindus­tries, is unusual in terms of its depth, tidal range, salinity, tempera­ture, and marine life. Many of the singular features of the Gulf ofCalifornia (also known as the Sea ofCortez) may be explained byitsshape and bottom profile, both ofwhich are reflections of the gulf'sgeologic history. This article summarizes the unique features ofthegulf, describes the theory of plate tectonics, explains how tectonicsmay have affected the geologic evolution and physiography of thegulf, and illustrates the process by which the Colorado Riverbecame linked to the gulf.

Natural Features of the Gulf

The Gulf of California is approximately 1,100 kilometers inlength and ranges from 48 to 241 kilometers in width (Figures 1 and2). Its long and narrow shape influences its tidal range, which is thethird highest in the world and can reach almost 10 meters in thenorthern section (Flessa and Eckdale, 1987). The shape of the gulfis analogous to a bathtub, and the tides, which are greatest at thenorthern and southern ends and almost nonexistent in the middle,resemble water in a bathtub that sloshes back and forth when dis­turbed.

The high salinities and temperatures of the shallow water in thegulf are partially due to its shape, which restricts interchange ofwater between the gulf and Pacific Ocean. Salinities vary from 36to 39 parts per thousand. (The salinity of normal seawater isapproximately 35 parts per thousand.) In the northern gulf, surfacewater temperatures range from approximately310 in the summer to110 in the winter (Brusca, 1980). The depth of the gulf also affectstemperature and salinity by increasing heating and evaporationrates. The gulf is shallow (generally less than 200 meters) at itsnorthern end but deepens to the south. Parts of the southern two­thirds of the gulf range from 2,400 to 3,600 meters in depth, withtroughs plunging as deep as 4,060 meters (Brusca, 1980). Severalshallower troughs are also present in the northern section close totheBaja California coastline. The edges ofthese troughs are the sitesof upwelling, which brings cold nutrient-rich water to the surface.The organisms that feed upon the nutrients attract, directly orindirectly, a wide variety of other animals, including shrimp, tuna,whales, dolphins, sea lions, sharks, sea birds, and humans.

Plate-Tectonic Theory

Th~Gulf of California began to form 4 to 6 million yeats (m.y.)ago during the late Miocene as Baja California separated from theMexican mainland (Moore and Curray, 1982; Stock and Hodges,1989). The geologic events that forced the gulf open and split offBaja California were driven by global-scale forces. The theory ofplate tectonics describes these geologic processes.

The Earth's crust and uppermost mantle, collectively known asthe lithosphere, are composed of 8 to 10 large discrete blocks orplates and many smaller plates (Figure 3). The oceanic parts of theplates are 80 to 100 kilometers thick; the continental portions aretypically 110 kilometers thick or more (Sawkins and others, 1978).

60"N

oceanic plate is generally thrust (subducted>beneath the continent (Figure 4B). Platedestruction and plate formation balanceeach other, preserving the Earth's total surfacearea. Plate-tectonic theory suggests thatsubduction is actively occurring at tboundaries ofmost oceanicand continentplates in the Pacific Ocean. The PacificPlate, for example, is being subductedunderneath Asia near Japan; the associatedmelting of this oceanic crust formed theJapanese islands and accounts for the activevolcanism in this area. Collision of the Eur­asian and Indian Plates, both continentalplates, created the Himalaya Mountains asthe plates collided and one overrode theother. The resulting mountains are under­lainbycrust that is approximatelytwice theaverage thickness of continental crust.

Plates may also move past one anotherby shearing along faults that parallel theplates' motion (Figure 4C). This type ofinteraction along a transform boundarycreates large stresses in the Earth's crust.The San Andreas fault represents the bound­ary between the Pacific and North Ameri­can Plates, which are moving past eachother.

Plate-tectonic theory not only describesthe relative motion between crustal platestoday, but also provides a useful frame­work for reconstructing the positions ofplates in the past. For example, during thelate Paleozoic and early Mesozoic eras, ap­proximately 225 m.y. ago, all of the conti­nents were assembled into one large conti­nent, known as Pangaea. Evidence for t!lAe~dstence of Pangaea comes from man'"sources, including the distribution of"matching" rocks and fossils of the sameage on different continents, the shapes ofthe continents, and paleomagnetic data.

The Glossopteris flora, an assem­blage of Permian (286- to 245­m.y.-old) plant fossils, is pres­ent in Africa, Australia, India,Madagascar, South America,and Antarctica. Africa and SouthAmerica fit together like piecesof a puzzle. They formed asingle continent that was riftedapart and separated by sea­floor spreading, which createdthe Atlantic Ocean. Paleomag­netism, the relict magnetismwithin magnetic minerals inrocks, represents the state ofthe Earth's magnetic field atthe time the rock was formed.The direction ofthe paleomag­netism may be compared withthe magneticfield at other loca­tions and other times. Paleo­magnetic data, therefore, mayserve as compass needles, al­lowing geologists to reconstructthe geographical distribution.and motions ofoceans and COl.tinents during the past.

The changing positions of

60"E

Each plate moves with respect to the otherplates. The boundaries between platesaccommodate this motion and are the sitesof several types of geologically importantprocesses (Figure 4). Earthquakes, for ex­ample, are often associated with tectonicboundaries.

Plates maymove apart, leaving a gap (orrift) in between that fills with new moltencrustal material. The newly formed crust ishot relative to the crust surrounding it andrises to form ridges (or rises; Figure 4A).Spreading occurs as the new crust is addedon either side of the rift, being injectedbetween older crust as the plates moveapart. This process occurs in both oceanicand continental crust. Long continuoussystems of troughs and ridges characterizespreading areas on oceanic plates. Spread­ing in continental settings breaks conti­nents apart. The Great African Rift Valleyin eastern Africa is an active example ofcontinental rifting.

Driven by spreading forces, plates maymove toward one another and collide. Oneplate may be pushed under another or theplates may slide past each other. Oceaniclithosphere is denser and heavier than con­tinentallithosphere, and consequently the

Figure 2 (left). Location of the Gulf of California, Colo­rado River, Salton Sea, and San Andreas fault system,which includes several associated faults. Modified fromHamilton, 1961, p. 1309.

Figure 3 (below). Major plates of the world. The types ofplate boundaries, marked by heavy lines, rire as follows:(A) Midoceanic ridges at which the plates move apart arerepresented by double lines; (B) Transform fault bound­aries are shown by single lines; and (C) Trenches andother subduction zones are marked by lines with teethon one side; the teeth point down the descending slab.Dashed lines are used where the exact location or natureof the boundary is uncertain. From Sawkins and others,1978, p.163.

40'

30'

Antarctic plate

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120'

Francisco '\

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CALIFORNIA \.

\\\\

110'

............100km

30'

120"

2 Arizona Geology, vol. 20, no. 2, Summer 1990

25°

115°

Salton\ Sea

KEY:

PacificOcean

L......-....J100km

ftranSformfault

spreadingcenter

25°

20"

30°

115°

110"

and sea-floor drilling throughout the gulfhave contributed to unraveling its history.In the Guaymas basin near the middle ofthe gulf, for example, accumulation ratesfor the late Pleistocene and Holocene (2m.y. ago to the present) may exceed 2 me­ters per 1,000 years in some areas (Currayand others, 1982). Bathymetry (the mea­surement of ocean depth and topography)and geophysical magneticand seismic datareveal the presence of three active trans­form faults separated by two narrow troughsin the Guaymas basin (Bischoff and Henyey,1974). The troughs are sites of active spread­ing, where an estimated 5 to 6 centimetersof new crust are added each year (Larsonand others, 1972; Moore and Curray, 1982).

Figure 5. Transform faults and spreading centers in theGulf ofCalifornia. Note: Faults associated with the SanAndreas fault system are shown in greater detail than inFigure 2. Modified from Moore, 1973, p. 1886.

ofthe gulf, subduction occurred onthe westside of BajaCalifornia, which was then partofthe Mexican mainland. Subduction ceased,however, offthe Baja coast 10 m.y. ago, andthe juncturebetweenthe two plates becamea transform boundary (Atwater, 1970; Fig­ure 4C). By 6 to 4 m.y. ago the marginstrengthened, probably as it cooled andbecame more rigid, and a weaker inlandzone broke to accommodate the shearingmotion between the two plates (Atwater,1970). The shift of this plate margin hadtwo important results: Baja California wasripped off of the North American Plate andbecame part of the Pacific Plate, and theGulf of California was created (Atwater,1970). Both Baja California and a largeportion ofsouthern California are now partof the Pacific Plate, which continues to movenorthwest with respect to the North Ameri­can Plate. Baja California, in fact, has movedapproximately 300 kilometers to the north­west from its original position on the NorthAmerican Plate (Moore and Curray,1982).

Reconstruction of the positions of BajaCalifornia and the Mexican mainland re­veals that a large embayment existed in thecontinent during the late Miocene (12 to 5m.y. ago), priorto the opening ofthe Gulf ofCalifornia. Evidence for this embayment,known as the "proto-gulf," includes thedistribution ofmarine and nonmarine sedi­mentary rocks and changes in volcanicpatterns that predate rifting (Stock andHodges, 1989). Several mechanisms havebeen invoked to explain the existence oftheproto-gulf, including Basin and Range ex­tension, which is related to the widespreadmountain-forming episode that occurred inArizona during this time, and extensionassociated with development ofthe Pacific­North AmericanPlateboundary (Stock andHodges, 1989). This extension may haveweakened the crust underlying the proto­gulf and facilitated the onset of rifting (Stockand Hodges, 1989).

Tect()nismand SedimentationPatterns in the Gulf

The spreading center in the Gulf of Cali­fornia does not form a straight line ofridgesand troughs because both spreading andtransform motion are occurring. This cre­ates a zigzag pattern of troughs and faults(Figure 5). The floor of the gulf contains aseries of parallel faults aligned with themotion ofthe PacificPlate and separated bysmall deep troughs, which are the sites ofspreading and are approximately perpen­dicular to the faults.

Estimated sedimentation rates withinthe gulf are high, especially in the northernpart. This area received large volumes ofsediment from the Colorado River beforethe 20th century. The thick cover of sedi­ments that blankets the floor of the gulfobscures many of the features associatedwith both rifting and transform faulting;however, data from geophysical surveys

Tectonic History of the Gulf

Both the physical characteristics and theorigin of the Gulf of California are inti­mately tied to tectonic processes. The gulfis bounded on the northeast by the NorthAmerican Plate, which includes the NorthAmerican continent, and on the southwestby the Pacific Plate, which is current!y movingnorthwest with respect to the North Ameri­can Plate. The San Andreas fault system ispart of the boundary between these twoplates. The East Pacific Rise, a spreadingsystem on the Pacific Plate near its bound­ary with the North American Plate (Figure

A'3), has been partially subducted under­~eaththe North American Plate during the

past 30 m.y. (Atwater, 1970). In the vicinity

Figure 4. Three types of plate boundaries and relativeplate motions. (A) Divergent (plates move away fromeach other): the process ofsea-floor spreading creates newoceanic lithosphere; (B) Convergent (plates approach eachother): the process ofsubduction destroys lithosphere; (C)Transform (plates slide past each other without approach­ingordiverging): transform faulting is the corresponding

.rocess. Modified from Sawkins and others, 1978, p.165.

crustal plates have affected many of theEarth's systems. The positions of conti­nents and oceans, for example, influenceoceanic and atmospheric current patterns.These, in turn, significantly affect globalclimate. Plate tectonics also plays a role inpolar glaciation. Along with periodic, fa­vorable climatic conditions, resulting fromchanges in the Earth's orbit, the presence ofa land mass or continent near or over thepole is necessary for polar glaciation. Aspolar ice accumulates, sea level drops world­wide and ice sheets spread over the conti­nents.

Arizona Geology, vol. 20, no. 2, Summer 1990 3

Figure 6. Distribution of the Bouse Formation. FromSmith, 1970, p.141S.

---~---Mix leo) Yuma

The Salton Trough and Colorado River

At its northern end, the Gulf of Califor­nia spreading system is linked with theSalton Trough and the San Andreas faultsystem (Figure 5). The Salton Trough is astructural continuation of the Gulf of Cali­fornia that has been cut off from the gulfbysediments deposited by the Colorado River.It ineludes the Colorad0 River delta and theMexicali, Imperial, and Coachella Valleys.In some areas, the floor of the trough liesmore than 402 meters below sea level (Brusca,1980). The northern gulf and proto-gulfonce extended into the trough, forming alarge embayment at various times duringthe late Miocene and early Pliocene, ap­proximately 11 to 3 m.y. ago (Metzger,1968).

Although geologists dispute when andwhere the Colorado River began flowinginto the gulf, evidence suggests that thelocal drainage system that developed at thenorthern e!ld of the gulf eventually joinedthe Colorado River during the late Mioceneto early Pliocene (5.5 m.y. ago; Lucchitta,1972, 1989). The absence of older depositsassociated with a south-draining river sys­tem in southwestern Arizona and the pres­ence of basin sediments deposited by inte­rior drainages support this scenario (Eberlyand Stanley, 1978). The depositional condi-

Atwater, Tanya, 1970, Implications of plate tectonicsfor the Cenozoic tectonic evolution of westernNorth America: Geological Society of AmericaBulletin, v. 81, p. 3513-3536.

Bischoff, J.L., and Henyey, T.L., 1974, Tectonic ele­ments of the centralpart of the Gulf of California:Geological Society of America Bulletin, v. 85, p.1893-1904.

Brusca, RC, 1980, Common intertidal invertebratesof the Gulf of California: Tucson, University ofArizona Press, 513 p.

Curray, J.R, Moore, D.G., Aguaryo, J.E., Aubry,M.P., Einsele, G., Fornari, D., Gieskes, J., Guer­rero-Garcia, J., Kastner, M., Kelts, K., Lyle, M.,Matoba, Y., Molina-Cruz, A., Niemitz, J., Saun­ders, A., Schrader, H., Simonett, B.RT., and Vac­quier,V., 1982,Guaymasbasin: Sites 477,478, and481, in Curray, J.R, and Moore, D.G., eds., Initialreports of the Deep Sea Drilling Project: Wash­ington, D.C, U.S. GovernmentPrintingOffice, v.64, pt. 1, p. 211-415.

Eberly, 1.D., and Stanley, T.B., Jr., 1978, Cenozoicstratigraphy and geologie history of southwest­ern Arizona: Geological Society of AmericaBulletin, v. 89, p. 921-940.

Flessa, K.W., and Eckdale, A.A., 1987, Paleoecologyand taphonomy of Recent to Pleistocene inter­tidal deposits, Gulf of California, in Flessa,K.W.,ed., Paleoecology and taphonomy of Recent toPleistocene intertidal deposits, Gulf of Califor­nia: Paleontological Society Special Publicationno. 2, p. 2-33.

Hamilton, Warren, 1961, Origin of the Gulf of Cali­fornia: Geological Society ofAmerica Bulletin, v.72, p. 1307-1318.

Larson, P.A., Mudie, J.D., and Larson, RL., 1972_,".Magnetic anomalies and fracture-zone trends i ,the Gulf of California: Geological Society 0 . i

America Bulletin, v. 83, p. 3361-3368.Lucchitta, Ivo, 1972, Early history of the Colorado

Riverin the Basin and Range Province: Geologi­cal Society of America Bulletin, v. 83, p. 1933­1948.

__1989, History of the Grand Canyon and of theColorado River in Arizona, in Jenney, J.P., andReynolds, S.J., eds., Geologic evolution of Ari­zona: Arizona Geological Society Digest 17, p.701-715.

Metzger, D.G., 1968,The Bouse Formation (Pliocene)of the Parker-Blythe-Cibola area, Arizona andCalifornia, in Geological Survey research 1968:U.S. Geological SurveyProfessional Paper 600-D,p.126-136.

Moore, D.G., 1973, Plate-edge deformation andcrustal growth, Gulf of California structuralprovince: Geological Society of America Bulle­tin, v. 84, p. 1883-1906.

Moore, D.G., and Curray, RJ., 1982, Geologic andtectonic history of the Gulf of California, inCurray, J.R, and Moore, D.G., eds., Initial re­ports of the Deep Sea Drilling Project: Washing­ton, D.C., U.S. GovernmentPrinting Office, v. 64,pt. 1, p. 1279-1294.

Reisner, Marc, 1986, Cadillac desert; the AmericanWest and its disappearing water: New York,Viking Penguin Inc., 582 p.

Sawkins, F.J., Chase, CG., Darby, D.G., and Rapp,George, Jr., 1978, The evolving Earth: A text inphysical geology: N ew York, Macmillan Publish­ing Co., 558 p.

Smith, P.R, 1970, New evidence for Pliocene marineembayment along the lower Colorado River area,California and Arizona: Geological Society ofAmerica Bulletin, v. 81, p. 1411-1420.

Stock, J.M., and Hodges, K.V., 1989, Pre-Pliocena,extension around the Gulf of California and th.'transfer of Baja California to the Pacific Plate: •Tectonics, v. 8, p. 99-115.

dramatically decreased by human activi­ties. In the future, the geologic history ofthe Gulf of California will be affected notonly by natural processes but also by humanintervention.

References

tions of the Bouse Formation, which con­sists of Miocene-Pliocene estuarine depos­its exposed along the Colorado River fromYuma to north of Parker (Figure 6), becomeprogressively less salty to the north (Metz­ger, 1968; Smith, 1970). This requires aninflux of fresh water during deposition ofthe Bouse Formation, which suggests thatthe ancestral Colorado River had begun todrain into the Bouse embayment and, ulti­mately, the Gulf of California (Lucchitta,1972,1989).

The Colorado River progressively filledthe estuary with sediments until its deltareached the Salton Trough. The ImperialFormation (Miocene-Pliocene age) of theSalton Trough area contains a well-definedhorizon, above which are fossils in rocksthat were derived from the Colorado Pla­teau. These fossils record the integration ofthe northern Colorado River with the south­ern drainages in the Salton Trough area(Lucchitta, 1972, 1989). The delta depositsof the Colorado River eventually extendedthe entire width of the northern gulf, isolat­ing the Salton Trough from the gulf. (With­out the Colorado River delta, the gulftodaywould extend northward to approximatelyPalm Springs.) The river alternated its flowbetween the isolated trough, which becamea lake, and the northern gulf, but currentlyflows only into the gulf. The lake dried upand remained dry until 1905, when floodsdestroyed the headworks of an irrigationcanal and diverted the Colorado River intothe fertile Imperial Valley. For 2 years, theentire river flowed down the canal andemptied into the trough. The canal wasrepaired in 1907, leaving behind the no­outlet Salton Sea (Reisner, 1986).

Human activities have also affected theColorado River delta and the Gulf of Cali­fornia. Before the 20th century, sedimentscarried by the river made their way as farsouth as La Paz, approximately 1,000 kilo­meters from the river's mouth. With theconstruction of ir- rigation projects inthe Imperial Valley and damsalong the Colorado Riv-er, river flow into thegulf has been re-duced to almostz e r 0 (Brus-ca, 1980). Thea vera ge annualflow from 1902 to1934 was m 0 r ethan 15 mil- lion acre-feet, as mea- sured nearYuma. From 1935to1964,the annual dis- charge of riverwater into the gulf decreasedto slightly more than 4 millionacre-feet, and by the late 1960's only sub­surface percolation and diverted flowsreached the gulf. Colorado River water thatdoes flow into the gulf is typically very sa­line and polluted by pesticides and fertiliz­ers (Brusca, 1980). Both sedimentation andinput of fresh water, th~refore, have been

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Arizona Geology, vol. 20, no. 2, Summer 1990

The Nonfuel Mineral Industry: 1989 Summary,With Focus on the Southwest

by Michael N. Greeleyu.s. Bureau of Mines

In 1989, the value of nonfuel mineralproduction continued to rise in the South­west. Preliminary figures show that thetotal value of production in this regionexceeded one-third of the total productionin the United States. Mines in the six south­western states of Arizona, California, Colo­rado, Nevada, New Mexico, and Utah pro­duced almost $ll-billion worth of mineralproducts, compared to the national produc­tion total of $32 billion (Figure 1; Table 1).

Measured in dollars, the mineral outputin the Southwest increased more than 10percent over that of 1988. Mineral produc­ers in Arizona accounted for more than 10percent of U.S. nonfuel mineral wealth in1989, the largest State share of productionin the Nation, followed closely by output in

,.(>.. Arizona, A '3,190

Cali­forniaand Nevada (Figure 2).

These preliminary statistics were pub­lished by the U.S. Bureau of Mines (BOM),which has released State-by-State estimatesof nonfuel mineral production for 1989.These estimates, generally based on 9 monthsof data, have been published in one vol­ume: State Mineral Summaries--1990. This

_volume is designed to be a companion re­~ort to another BOM publication, Mineral

Commodity Summaries-1990, which contains

Arizona Geology, vol. 20, no. 2, Summer 1990

national statistics on 82 nonfuel minerals.Excerpts from both volumes appear below.Single copies of each are free from thePublications Distribution Section, U.s. Bu­reau of Mines, Cochrans Mill Rd., P.O. Box18070,Pittsburgh,PA15236. Final produc­tion figures for 1989 are expected to beavailable in August.

The State summaries were prepared byState mineral officers from the BOM, incooperation with the respective State min­eral agencies. Individual summaries arealso published separately as State MineralIndustry Surveys. Copies are availablefrom the respective State mineral officers:Fred V. Carrillo, 1605 Evans Ave., Reno, NV89512 (California and Nevada); Michael N.Greeley, 201 E. 7th St., Tucson, AZ 85705(Arizona, NewMexico, and Utah); and JaneP. Ohl, Bldg. 20, Denver Federal Center,Denver, CO 80225 (Colorado).

1989 Value of NonfuelMineral Production,

Southwest Region(Millions of Dollars)

U.S. SUMMARY

The estimated value ofnonfuel mineralproduction in the United States increasedabout 6 percent in 1989 over that of theprevious year. Metal production, repre­senting about 37 percent of the total value,rose 14 percent from $10.2 billion in 1988 to$11.6 billion in 1989. Although the value ofindustrial minerals, at $202 billion, accountedfor 63 percent ofthe 1989 total, the increaseover that of 1988 was less than 2 percent.

Limited supply and low inventoriesmaintained the copper price above $1 per

pound, and U.S. copper-mine productionincreased about 5 percent during 1989. InFebruaryan agreement was reached on theterms for an International Copper StudyGroup, which was conceived more than 2years ago by the United States.

Domestic gold mines continued to pro­duce at record levels during 1989; activitywas centered in Nevada, California, andMontana. Gold exploration declined slightlyfrom the previous year, but continued tooutpace exploration for other commodities,both domestically and internationally.Weakening prices throughout the yearapparently reflected an easing of worldpolitical tensions and expectation of in­creasing inflation. Gold price declines alsocontributed to the closure of marginal gold­mining operations.

Domestic silver production increased forthe third consecutive year, despite a drop inthe average silver price, because of theopening of several new mines that recoversilver as a byproduct. Notable among thenew mines is Greens Creek, a large zinc­silver-lead mine in Alaska, which at fullcapacity is expected to be one of the largestdomestic silver-producing mines. As inrecent years, most of the new mines thatopened in 1989 aregold mines where heapleaching is used to recover precious metalsfrom low-grade ores.

A continuing, tight supply-demand situ­ation resulted in record-high zinc pricesand the opening of six zinc-producing minesin the United States. Domestic mine pro­duction rose for the third straight year;domestic smelters operated near capacityin 1989, producing the most metal since1981. U.S. production could double in 1990,largely because of rising output at the RedDog mine in Alaska.

World demand for lead, at about 6 mil­lion metric tons, was a record high. Thisresulted in the highest average price on theLondon Metal Exchange since 1981 and thehighest average domestic price since 1980.Production increased considerablybecauseofnewzinc-silver-lead mines in Alaska andMontana and a reopened mine in Idaho.Much of this production was exported be­cause of limited smelter capacity. The UnitedStates was expected to become a major ex­porter oflead concentrates, slarting in 1990.

Strong overall demand diminished ex­cess inventories of molybdenum and pro­duction increased, compared with that of1988. Although steel demand for molybde­num weakened slightly, prices were stablebecause the market remained in balance.One domestic producer reopened its pri­mary molybdenum mine in Questa, NewMexico.

5

TabId. Value of nonfuel mineral production in the Southwest, measured by mine shipments, sales, or marketable pro­duction, including consumption by producers. All figures are from the U.S. Bureau ofMines; totals for 1989 are prelimi­nary estimates.

Value (thousands Percent of TotalState of dollars) Value in 1989 Principal Minerals

1988 1989 Southwest U.S.

Arizona 2,773,411 3,190,266 29.3 10.0 copper, molybdenum, sand & gravelCalifornia 2,708,768 2,839,141 26.1 8.9 sand & gravel, cement, boronColorado 364,005 442,911 4.1 1.4 molybdenum, sand & gravel, cementNevada 1,944,566 1,996,062 18.4 6.3 gold, silver, sand & gravelNew Mexico 1,022,672 1,164,882 10.7 3.7 copper, potash, sand & gravelUtah 1,014,847- 1,241,484 11.4 3.9 copper, gold, magnesium metalSOUTHWEST 9,828,269 10,874,746 100.0 34.2U.S. TOTAL 30,021,452 31,810,960 100.0

Tab/e2. Value ofnonfuel mineral production in Arizona,measured by mine shipments, sales, or marketable pro­duction, including consumption by producers. All fig­ures arefrom the U.S. Bureau ofMines; totals for 1989arepreliminary estimates.

Value (thousands of dollars)1988 1989

Mineral

Clays 1,590 2,010Copper 2,246,093 2,592,723Diatomite 1,208 1,208Gem stones 3,300 3,300Gold 64,106 35,264Lime 29,637 WSand and gravel

Construction 123,854 133,500Industrial 3,045 W

Silver 31,974 27,236Stone

Crushed 33,000' 26,200Dimension I' 1

Other" 235,596 368,824TOTAL 2,773,411 3,190,266

W Withheld to avoid disclosing company pro­prietary data; value included in "Other" figure., Estimated." Combined value of cement, lead (1988), mo­lybdenum, perlite (1988-89), pyrites, salt, tin(1988-89), and values indicated by symbol W.

metals and low-costleachablecopper. Golddiscoveries were announced at the MexicanHat property in Cochise County and nearYarnell in Yavapai County. Although nonew deposits of leachable copper were re­ported during 1989, several properties, in­cluding the Cochise in Cochise County andSanchez in Graham County, were exten­sivelyevaluated for possible development.

The value of industrial mineral produc­tion was about $290 million. Arizona rankedsixth in the Nation in production of con­struction sand and gravel, which remainedthe largest component of the State's indus­trial mineral output. Cement, lime, andcrushed stone were also major contributors.In addition, Arizona mines held their posi­tion nationally among the leading produc.ljers of bentonite and naturally occurrin Jbgem stones.

Figure 2. T S Ary (center), Director of the U.S. BureauofMines (BaM), recently visited the Arizona GeologicalSurvey to discuss nonfuel mineral production and metal­lic mineral districts in Arizona. With him are Michael N.Greeley (right), BaM State Mineral Officer for Arizona,New Mexico, and Utah, and Larry D. Fellows (left),Director of the Aritona Geological Survey.

Preliminary figures indicate that the valueof output in the State totaled about $3.2billion, an increase ofIS percent over that of1988 (Table 2). Supporting the first-placeposition was the high value ($2.9 billion) ofmetallic minerals mined in Arizona. Thisamount rE;!presented a quarter of the valueof all metals produced in the United States.Copper and molybdenum production wasthe highest of any State. Arizona was alsoamong the leading States in the productionofbentonite, cement, gem stones, lime, con­struction sand and gravel, and silver. TheState's rank in domestic production ofgold,however, dropped from 8th to 10th place.

Arizona mines produced approximately60 percent of the Nation's copper in 1989.Production reflected a S-percent increaseover the 1988 level, with a IS-percent in­crease in value. The producer copper pricerose from a 1988 average of$1.21 per poundto $1.31 in 1989. In general, major copperproducers in the State focused their atten­tion on expanding present operations andincreasing the percentage of productionachieved through the solvent extraction­electrowinning (SX-EW) process. Somecompanies produced more than 2S percentof their copper in SX-EW plants.

A coalition of public and private inter­ests continued an in-situ, copper-miningresearch project near Casa Grande in PinalCounty. The site was drilled to obtainmineralized samples and fracture-orienta­tion data from the buried Santa Cruz oxidecopper deposit. By yearend, five deep drillholes were completed. Plans were made toequip these holes for injection and recoveryof solutions and to test the deposit for per­meability characteristics.

Gold production decreased 37 percent in19~9. The decrease was primarily due to adrop in gold prices and to a cessation orreduction of mining operations at severalgold properties in the State. Silver produc­tion, which remained constant, was chieflyrecovered from copper ores or smelter fluxores. Arizona mines continued to increasetheir output ofmolybdenum. Productionin1989 was nearlyhalfofthe Nation's domes­tic supply.

Exploration in Arizona continued to beconcentrated on the search for precious

Arizona

Arizona mines led the Nation during1989 in the production of nonfuel minerals.

STATE SUMMARIES

U.S. demand for building and construc­tion materials, such as construction aggre­gate, gypsum, and cement, remained strongin 1989. Cement imports declined slightly,representing about 17 percent of apparentconsumption compared with 19 percent in1988. Mexico, supplying 29 percent of thetotal, was the primary source of imports,followed by Canada, Japan, Spain, andGreece. Mexico was also the target of anantidumping petition, filed byproducers inArizona, Florida, New Mexico, and Texas,who alleged that Mexican cement was beingsold in these areas at less than fair value.This was the second petition filed againstMexico in the last 3 years. TheInternationalTrade Commission made a preliminarydetermination that the cement industry inthese regions was materially injured byMexican imports.

U.S. demand for construction aggregateimproved for the fourth consecutive yearand was at a near-record level. The U.S.gypsum industry performed well, eventhough new housing starts decreased forthe third year in a row. Increased U.S. ex­ports ofgypsum wallboard and strength inthe remodeling markets offset the impact ofdeclining housing starts.

Potash producer's stocks, which had beenbuilt up during the winter of 1988-89 inanticipation of a strong spring demand,finished the year slightly down because ofa strong fall demand and extended mainte­nance shutdowns at mines that restrictedoutput. At the beginning of the year, theUtah sulfate of potash facility, which wasflooded by the Great Salt Lake in 1984,started operations with salts harvested fromthe ponds during the fall of 1988.

The U.S. salt industry was the largestproducer of salt in the world. Althoughoutput was relatively unchanged comparedwith that of the previous year, the structureofthe industry changed with mergers andacquisitions.

6 Arizona Geology, vol. 20, no. 2, Summer 1990

The U.S. Supreme Court issued a rulinginMay in a case involving royalties paidbymining companies for minerals extractedfrom State trust lands. The Court saidArizona must establish a method of assess­ing the "true· value" of the rninerals re-e moved. The State will now require miningcompanies to pay a minimum royalty of 2percent of the gross value of the mineralremoved from trust lands, with possibleincreases in the future.

California

California was the second leading Statein the Nation in the production of nonfuelminerals during 1989. The value of com­modities produced was estimated to be $2.8billion, a 5-percent increase over that of1988. California led all States in the produc­tion of asbestos, boron minerals, portlandcement, diatomite, calcined gypsum, rare­earth concentrates, construction sand andgravel, and tungsten. It was second in theproduction of natural calcium chloride, feld­spar, gold, byproduct gypsum, magnesiumcompounds from seawater and brines, andsodium compounds.

Gold exploration in California contin­ued, although at a slower pace than theprevious year as lower prices and newregulations dampened enthusiasm forprecious-metal exploration. Nearby resi­dents, environmentalists, and no-growthproponents continued to impede miningoperations throughout the State as they

_ opposed the issue of new mining permits• by local governments to sand-and-gravel

quarries and gold-mining facilities. Opera­tions were shut down at several gold minesduring the year.

New gold-mining operations, however,at the American Girl Canyon project wereapproved and construction began early inthe year at the mine in Imperial County. InMarch production began at the RoyalMountain King gold mine in CalaverasCounty and development was initiated atthe Hayden Hill mine in Lassen County.

One cement company and the Port ofRichmond discussed the possible develop­ment of an $11-million bulk-cement distri­bution facility north of the Port's containerterminal. The facility would use a high­capacity pneumatic unloading system andan underground piping network to removecement from incoming ships and transportit to silos to await loading onto other shipsand railcars.

The State Regional Water Quality Con­trol Board became the sole regulator ofmining wastes after passage of AssemblyBill 1413 in November. The bill reflectedrecommendations of a mining-waste studythatthe UniversityofCalifornia at Berkeleyconducted. This study endorsed eliminat­ing dual permits and shifting regulatory

._ authority for mining-waste matterS from

.., the Department of Health Services to theWater Board.

Arizona Geology, vol. 20, no. 2, Summer 1990

Colorado

The estimated value ofnonfuel mineralsproduced in Colorado in 1989 was $443million, compared with $364 million in 1988.This 22-percent risewas mainlydue to unit­price increases for molybdenum, construc­tion sand and gravel, and zinc and a sub­stantial production increase for molybde­num. The State ranked 23d in the Nationinnonfuel mineral production and accountedfor 1.4 percent of the total U.S. value.

Colorado ranked 11th among 25 metal­producing States, accounting for slightlymore than 2 percent of the Nation's totalmetals value. Molybdenum ranked first inColorado in value, followed by sand andgravel, portland cement, crushed stone, gold,zinc, and other metals and industrial min­erals.

Metallic mineral exploration and somemine development continued in the State,particularly in Boulder, Oear Creek, Custer,Gilpin, and Ouray Counties. Molybdenummining and milling operations were on theupswing, principally because of the rise inprice of molybdic oxide to $3.80 per poundin 1989, from $3.44 in 1988. Output ofmolybdenum in concentrate rose to about36 million pounds annually, up from about30 million pounds in 1988. At the end ofDecember, however, plans were announcedto cut production at the Henderson mineby15 percent, beginning the first week in January1990. The cut is due to lower marketplacedemand.

The total gold output in the State plum­meted 48 percent. The London mine inPark County was closed in June after beingin production for slightly more than a year.The Summitville surface mine was alsoclosed in Junewhen a crack was discoveredin the embankment of the leach pad. Be­cause of a citizens' lawsuit, mining planswere delayed atthe San Luis gold project inCostilla County.

Zinc production in Colorado was esti­mated to be the same as in 1988, but totalvalue increased nearly 37 percent as the av­erage price ofzinc rose to 81¢ per pound.Out­put of copper, lead, and silver, however,decreased considerably during the year.

Portland-cement output in Colorado wasup about 9 percent; total value increased anestimated $4.6 million to $53.5 million in1989. Estimated crushed-stone productionfor 1989 fell to 8.4 million short tons from10.6 million in 1988. More than half of thecrushed-stone output was granite; one-thirdwas crushed limestone.

Nevada

Nevada's 1989 nonfuel mineral produc­tion was estimated to be valued at $2 bil­lion, an increase of $52 million from 1988.An almost 21-percent rise in gold produc­tion to an estimated 138.1 million kilograms(4.4million troy ounces) accounted for mostofthe increase. Silv~r production dropped

24 percent to 463 metric tons. Nevada wasthe leading State in the Nation in the pro­ductionofgold, silver, and barite; second inthe production of diatomite, fluorspar, andlithium; and the sole producer of minedmagnesite and mercury. Nevada rankedthird among the States in the total value ofnonfuel mineral production.

The search for precious metals contin­ued to dominate Nevada mineral explora­tion. Drillingand exploration projects werereported throughout the State, particularlyin Elko, Esmeralda, Eureka, Humboldt,Mineral, Nye, and White Pine Counties.Important new discoveries were reportedin the Roberts Mountain area of EurekaCounty and in the Carlin Trend. At least 11mining companies continued explorationefforts in Eureka County. In HumboldtCounty, additional exploration was con­ducted at the Getchell property and severalcompanies explored the area surroundingthe Marigold mine. Exploration in NyeCounty included drilling at the Mother Lodeproject near Beatty and in the ToiyabeMountains and investigating the west sideof the Monitor Range and the ToiyabeNational Forest. Exploration was also con­ducted near Silver Peak in Esmeralda Countyand at the Wind River mine in WashoeCounty.

Gold production continued to increase,despite a drop in the average annual pricefrom $439 per ounce in 1988 to about $389per ounce in 1989. Major expansions wereunderway or completed at six gold minesand at operations in the Carlin Trend. Fivenew mines opened during the year, one ofwhich includes a $27-million bio-oxidationmill that uses soil bacteria to handle refrac­torysulfide ore. Mine constructionbegan attwo additional properties.

The Nevada legislature concluded itslongest biannual session in history withchanges in Nevada's tax laws on miningprofits and the first mine land-reclamationlegislation in the State's history. SenateJoint Resolution 22, passed by both thelegislature and a vote of the people, changedthe net proceeds of mine tax from 2 percentto 5 percent. Additional proposed miningseverance taxes were defeated. AssemblyBill 958, which placed responsibility for ad­ministrating a new reclamation program inthe Nevada State Department of Environ­mental Protection, was passed in the clos­ing days of the session.

New Mexico

Thevalueofnonfuel mineral productionin New Mexico reached an estimated $1.2billion in 1989, a 14-percent increase overthat of1988 and a record for the State. Mineoutput placed New Mexico 10th among allStates in nonfuel mineral production. Mostofthe increase was due to the rise in outputfrom New Mexico's metal mines, especiallythose that produced copper, molybdenum,and zinc. The metals sector contributed

7

more that $800 million, or 71 percent of thetotal value ofnonfuel minerals produced inthe State. Metal production in New Mexicoranked fifth nationally.

Copper production-remained relativelyconstant, showing only a modest increasein 1989. The total mine output, however,sustained the State's position as the secondleading source of primary copper in theNation.

The life ofthe Tyrone open-pit mine willbe extended through 1991. Strong copperprices will allow the company to mine alower-grade ore body. Operation ofthe SX­EW facility, however, is expected to con­tinue for 15years. The Tyrone mine was thethird largest producer of copper in the countryin 1989; the Chino mine was the fourthlargest.

A large deposit of yttrium and zirco­nium was discovered on the MescaleroApache Indian Reservation in Otero County.Reserves were estimated to be 2.7 millionshort tons containing 0.18 percent yttriumoxide and 12 percent zirconium oxide. Whenit begins producing, the deposit will be thefirst primary source of yttrium in the UnitedStates.

The value of industrial mineral produc­tion in 1989 was estimated at $336 million.Potash production led all nonmetallic out­putby a large margin. Underground mineswere responsible for more than 88 percentof potash production in the Nation. Outputvalue increased 17 percent over that of1988and represented more than one-fifth of thetotal nonfuel mineral production in the State.Six mining and processing facilities in theCarlsbad area maintained operations

8

throughout the year.In November, the U.S. Bureau of Land

Management signed an order extendingthe royalty rate on all Federal potassiumleases in New Mexico. About 85 percent ofthe total potash mined in the State has beenon Federal leases. The royalty rate for thenext 2 years will continue to be 2 percent ofthe gross value of output at the point ofshipment.

Perlite, construction sand and gravel,and crushed stone were also major con­tributors to the total value of industrialminerals. The production ofperlite was thelargest in the Nation and pumice outputwas second.

The 1989 State legislature enacted Sen­ate bill 303, designating the director of theNew Mexico Bureau of Mines and MineralResources as the StateGeologist. House bill526 gave the Mining and Minerals Divisionof the New Mexico Energy, Minerals, andNatural Resources Department authorityover mine registration, annual reporting,and safeguarding of surface-mine open­ings. The bill also limited the duties of theState Mine Inspector to mine-safety train­ing and the enforcement of laws governingcertain underground operations. Jurisdic­tion of the Inspector's office was transferredto the New Mexico Institute of Mining andTechnology.

Utah

Thevalue ofnonfuel mineral productionincreased 22 percent to more than $1.2 bil­lion, a record for Utah. Mine output placedUtah eighth among all States in nonfuel

mineral production. Most of the increasewas due to the strong rise in metal output,especially copper, gold, magnesium, mo­lybdenum, and silver. The metals sectorcontributed more than $1 billion, or 83percent, of the total value of nonfuel min- •..'....eral production and ranked Utah fourth .11nationally in metal production. .

The search for nonfuel minerals wasmostly concentrated on precious-metaldeposits. Exploration activity was brisk forgold and silver in the mining districts oftheTintic area south of Salt Lake City and foradditional reserves of gallium and germa­nium near the Apex mine in southwesternUtah.

Dedicated in late 1988, the modernizedfacility at the Bingham Canyon mine sub­stantially increased production of copperand byproduct metals during 1989. Themine was the second largest producer ofcopper in the Nation. The Bingham Can­yon operation maintained its role as theonly producer of copper and molybdenumin Utah and as the State's largest producerof gold and silver.

North of Bingham, development wascompleted at the Barney's Canyon goldmine. The surface-mine and heap-leachingoperation produced its first gold in lateSeptember. Production is expected to con­tinue for 10 years at an average annual rateof 2,500 kilograms (80,000 troy ounces).

The Goldstrike mine in WashingtonCounty also began produdngin 1989. Annualproduction from this open-pit heap-leach-ing op.eration is expected to be 1,250 kilo- a.··.\grams (40,000 troy ounces) of gold and a .,JI)similar quantity of silver; the lifespan of the ­mine is estimated to be 5 years.

Management announced a $400-millionmodernization program for the integratedsteel facility near Orem, which will require3 to 5 years to complete. In October, steelproduction at the facility was reduced by 25percent because of a nationwide decline indemand.

Utah continued to lead the Nation as theprincipal domestic source of beryllium.Production and sales were down slightlyduring the year, however, because of re­duced demand in the defense, computer,and semiconductor markets. Although mineproduction of vanadium in southeasternUtah surged briefly in response to a tempo­rary price increase, total output for 1989declined from previous years. Magnesiummetal production at Rowley rose after anew evaporation and precipitation pondsystem was completed in 1988.

The value of industrial mineral produc­tionin Utah in1989 was about $211 million.Portland cement, followed closely by con­struction sand and gravel and salt, was thelargest component of the output. Lime,phosphate, potash, and crushed stone wereother important contributors. Utah wasone of the few States with mines that sup- 8liplied magnesium compounds and sodium.'sulfate during 1989.

Arizona Geology, vol. 20, no. 2, Summer 1990

The Future of Economic Geologyin Arizona:

A Perspective From Industry*

p

by Frederick T. GraybealChief Geologist, ASARCO, Inc.

180 Maiden Ln.New York, NY 10038

Changes have occurred in the explora­tion process, and as a result, the futureisn't what it used to be. Exploration de­partments and budgets of mining compa­nies are smaller. The exploration geologistin the porphyry copper decades of 1950 to1980 was primarily a field mapper and corelogger-a practical scientist. Claim staking,land work, drill management, core split­ting, geochemical sampling, and drafting- often done in the past by support staff ­are nowroutine tasks of the field geologist,which leaves less time for geologic work.Starting in the 1980's, exploration geolo­gists have been searching for preciousmetal targets in which the ore mineral isnearly invisible. As a result, the geologist isless a mapper and more a designer andmanager of assay quality-eontrol and sample­collection programs. The geologist nowrelies on the assayer instead of the handlens to determine if ore grades are present.Core logging is a lost art because most

A drilling is done by rotary methods that• provide small, hard-to-Iog muddy chips of

rock at the rate of a sample every fewminutes. Many geologists under the age of35 have never logged drill core, nor havethey learned the importance of carefulobservation of rocks. At times it seems likeexploration by remote control.

In addition to the exploration process,the nature of the participants has changed.Gold deposits are commonly small andtechnically simple to mine. They may bediscovered by low-eost surface prospectingand shallow drilling and developed at lowcapital cost. This means that small explora­tion groups can be important players. Manyof the small groups do not maintain perma­nent exploration offices, have no perma­nent exploration staff, and live in anotherState or country. They often operate with­out anyone knowing of their presence. Theyare numerous and move quickly; to com­pete, other mining companies must movequickly too. There is less time for science inthis type of environment. Some managershave proposed that geologists should notspend time summarizing the results ofexploration on submarginal drill projects.The next generation of explorers, if there isone, may have to repeat the work.

Corporate philosophy concerning explo­_. ration has also changed. In the past, mining,., companies explored because they were

expected to explore. Now exploration is

Arizona Geology, vol. 20, no. 2, Summer 1990

increas­ingly seen

as a businessfunction to be

evaluated onperformance. In other words, if one can'tfind something, one maynot continue to ex­plore. The net effect is more pressure,which is good, but pressure also increasesthe focus on short-term results, which maynot be good because it leaves less time forsystematic geologic study. As a commen­tary on these changes, I have seen far lessrecordingofgeologic data and thought duringthe 1980's than during the porphyry copperboom. Mine geologists do less mappingand more grade control than before, whichleaves the explorationist with a less com­plete database upon which new explora­tion models and concepts may be built.Theelegant exploration research groups run byAnaconda, Kennecott, and other compa­nies, which made significant scientific con­tributions to the literature, are a thing of thepast. They are not cost effective becausethey cannot provide new concepts quicklyenough to get a jump on the competition.

Most scientific research on ore depositsand exploration methods, whether gath­ered by industrial, academic, or govern­ment groups, is 4 to 10 yearsbehind discov­ery. In other words, exploration discoverydrives the science, not the reverse. Obvi­ously, one can't study an orebody until ithas been found.

Although scientific research does. notoften initiate major discovery cycles, it hascontributed significantly to the extension ofthose cycles. The numerous publicationson porphyry copper deposits from theUniversity of Arizona during the 1960'sand 1970's are good examples of this phe­nomenon. Science by academic and gov­ernment groups, however, is becomingincreasingly laboratory and computer ori­ented because that is :whatgets published in

peer-reviewed journals. These data arefar more rapidly collected than fielddata and reflect a response to the pres­sureon researchers to publish quicklyto

achieve tenure and the reputation re­quired to obtain research grants. The de­pendence on the laboratory is well illus­trated in an Eamomic Gecilogy article in whichsix coauthors from four prestigious researchgroups proposed an origin for a major oredeposit based on a single rock sample(Eldridge and others, 1988). As the currentgeneration of tenured economic geologyprofessors with careers balanced by fieldand laboratory work is gradually succeededby the laboratory experts, one wonderswho will teach the technique and impor­tance of field observations to future explo­rationists. Maybe industry will, or maybeindustrywill hire structural geologists whostill gather field data and teach them aboutore deposits.

It is rare to find a descriptive ore depositpaper based on field work in a peer-re­viewed journal. Yet, it is the field-baseddescriptive paper that most often containsthe clues useful to explorationists. Thesedescriptions identify the odd, single de­posit types that maybethe precursors ofthenext exploration model. Getchell and GoldAcres in Nevada, both classic Carlin-typegold deposits, were active mines 20 yearsbefore the Carlin mine was discovered anda major new deposit type finally recog­nized. The uranium mines at Beaverlodgein Saskatchewan and Rum Jungle in theNorthern Territory of Australia were knowndecades before the discovery of the majorunconformity-related deposits in the Ath­abaska Basin and Alligator River areas.Fine-grained gold occurrences in lateritewere known in Western Australia 30 yearsbefore the discovery of the giant Bodding­ton gold deposit near Perth. Descriptivefield information is not being recorded in aconsistent professional way in mines, dur­ing exploration, or in scientific journalsbecause of budget reductions and short­term philosophies and because it doesn'thelp in winning tenure or grants. Futurediscovery rates will suffer as a result.

In light ofthese observations, what is thefuture of economic geology in Arizona?Based on the data on porphyry copperdeposits, there will not be another surge incopper exploration at the current or ex­pectable copper prices. The discovery ratefor porphyry copper deposits fell precipi­tously in the 1970's because of significant

• Editor's note: This article is based on a talk thattheauthor, who was the invited luncheon speaker, gaveat a special symposium sponsored by the ArizonaGeological Society and the Arizona Section of theAmericanlnstitute ofProfessional Geologists. At thesymposium, which was held in Phoenix in Novem­ber 1989, summaries of geological activities werepresented by the directors of State and Federal geo­logical and mineral resource agencies and by repre­sentatives of the geology departments in the threemajor universities in Arizona. Dr. Graybeal's speechis reprinted here with permission.

9

increases in the depth of mineralizationwith time. Arizona has largely been sweptclean of porphyry copper deposits that areminable by open-pit techniques. Even ifdeep deposits could be located, the finan­cial risk of block caving would be high.

The gold rush has largely bypassedArizona. During the past 4 years, however,the discovery rate has substantially fallenin the traditional gold provinces of NorthAmerica, even though gold prices are still atprofitable levels. Geologists are now search­ing for greener pastures. A modest golddeposit was recently discovered at Yarnell,Arizona; coupled with apparent gold dis­roveries in carbonate rocks in northern Mexicoand in volcanic rocks near Pearce, Arizona,this discovery may indicate a short-termincrease in exploration activity in the State.

If one assumes that increased levels ofexploration and economic geology activi­ties are healthy for Arizona, the followingsuggestions might contribute to thathealth.

(1) Publications. The symposia pro­ceedings and guidebooks that contain shortdescriptive papers published by the Ari­zona Geological Society must continue. Thesepublications are important sources of de­scriptions ofore deposits and their el1viron­ments and fill a void left by many of themore instrumentally minded research or­ganizations and journals.

(2) Mining Claim Records. State andFederal agencies should keep a permanentand retrievable record of locations of allclaims staked or assessed in Arizona, alongwith owners' names and addresses. Thoseengaged in small-scale exploration activi­ties acquire potentially useful data, but of­ten their names and data are forgotten orlost. Contrary to popular opinion, keepingexploration data confidential is not ineffi­cient because information owned by onegroup is often reviewed by others underprotection of confidentiality agreements.Industry does not want exploration data inpublic files, but does want to know who didthe work. Unlimited access to explorationdata would compromise the interests ofshareholders of companies who paid forthe data. Second or third exploration effortsbythe same company on the same propertyhave been known to result in discovery, anopportunity that would otherwise be lost.The taker ofthe risk is entitled to keep thedata or to trade or sell it at his or her solediscretion, usually the only reward for therisk. Knowledge that work was done in anarea: would not compromise confidential­ity, but could increase long-term explora­tion efficiency.

(3) Mining District Research. Moregeologic research, including mapping atintermediate scales, is needed in miningdistricts to enlarge the exploration target.This includes geologic maps and studies ofedges of ore-forming systems. These bound­aries may exceed visual limits and be de­fined by fluid-inclusion paleothermal anoma­lies or stable-isotope patterns. This need

10

was a nearlyunanimous opinion expressedby exploration geologists in a 1981 surveyby the Society of Economic Geologists andin more recent panels, but has largely beenignored. A focused study of areas of de­tachment faulting, such as the Copperstonemine and other smaller Arizona gold de­posits, might stimulate exploration in whatis conceptually a very difficult geologicenvironment.* Most mapping exercises stopat the edges of orebodies, and the currentmSMAP effort by the US. Geological Surveyis too regional in scope for direct applica­tion to exploration.

(4) In Situ Mining. Mining researchagencies, such as the U.S Bureau of Minesand newly formed Copper Research Cen­ter, should increase research on in situ miningof copper oxides and sulfides. The currentresearch program by Asarco, Freeport, andthe U.S. Bureau of Mines at the Santa Cruzoxide deposit near Casa Grande will evalu­ate environmental permitting of an in situtest and obtain information on operatingcosts. This project has no guarantee ofsuccess and has endured the unpredictablecrises typical of any research program. Publicconcern about the impact of mining on theenvironment will increasingly influencemining development. In situ leaching of­fers a way to extract metal at lowcapital costwith no pits, collapse zones, dumps, tail­ings, or smelting. Aspects of in situ mininginvolve processes that are very similar toore deposition and supergene enrichment;experience at Santa Cruz has shown thatany research program in this field shouldbudget for extensive geologic input.

(5) Resource Estimates. Mineral-resource appraisals for land-use planningare dangerous. These appraisals are basedon known ore deposit models and shouldnot be used to declare areas barren of min­erals. Such appraisals are flawed becausethey are forced to estimate the abundanceof as-yet-unknown types of ore deposits aszero. Persons who state that all ore deposittypes are already known remind one of thedirector of the U.S. Patent Office, who sug­gested in 1899 that the office be closedbecause everything that could be inventedhad been invented.

(6) Industrial Minerals. Conventionalwisdom holds that, in the industrial min­eral business, one explores for markets andthen looks for ore; however, 100 years ofmining industrial minerals in the West,along with rapid population growth, havealmost depleted some of these ores. It maybe time to abandon conventional wisdomand explore for new deposits. A recent

• Editor's note: Geology and Mineral Resources of theBuckskin and Rawhide Mountains, West-Central Ari­zona, published after Dr. Graybeal's speech was pre­pared, is such a study. It focuses on the geology of aCordilleranmetamorphic core complex and the min­eralized areas along a detachment fault. Publishedby the Arizona Geological Survey asBulletin 198, this280-page report contains three large maps and maybe purchased for $35.50 (includes shipping charges).

workshop addressed this subject.*(7) Natural Resource Education. For­

mal secondary-school education in earthscience, natural resources, and the environ­ment should be required for every studentin the country. I'm sure many have experi- ."enced the vignette of a dinner conversatio;;eJiwith an eighth grader who announces, "Werepoisoning our environment, and it's indus­try's fault," then adds wisely, '1 learned itin school." Occasional lectures at schoolsbygeologist mothers and fathers areworth­while, as are industry-sponsored films onthe importance of natural resources, butthey are a needle in the haystack.

Nationwide statistics on secondary-schoolearth-science education are incomplete, butthe American Geological Institute (AGI) inAlexandria, Virginia has compiled somedata. New York requires 1 year of earthscience, typically in 9th grade, as part of itsRegents curricula. Montana, Idaho, andMaine offer earth science as an elective;these classes are accepted as college­preparatory laboratory-science courses. A1985-86 National ScienceTeachers Associa-tion survey, however, indicated that only30 percent of the Nation's schools offerearth science in any form. Although theAGI cautions that these data are incom­plete, they do seem to indicate that highschool students are earth-science illiterate,except possibly in New York. In addition,Green (1989) found that virtually all collegefreshmen who plan teaching careers willmajorin education, not in the field they willteach, which raises the question of whether& ...future geology teachers will know enough..geology to teach it.

Arizona, as a major producer of metals,consumer of water, and population growthcenter, should require that high school stu­dents study earth science and those teach­ing it have an adequate scientific back­ground. Waiting until college is too late.Furthermore, college-level, introductorygeology courses are not required of everystudent and miss those who never attendcollege. All students, however, may be­come voters. An understanding of naturalresource issues, flood-plain locations, andearthquake zones will make students moreeffective voters and is no less importantthan knowing how to dissect a frog, calcu­late angular momentum, or balance a chemi­cal equation. Education is a publicfunctionand requires leadership at the State-agencyor political level; an initiative from the miningindustry regarding natural resource educa-

(continued on page 12)

• Editor's note: This workshop, held to improve

public understanding off t:~,~~~;:r~'~~l;~iI~~;~;~:~~+minerals to Arizona's e,sored by the U.S. GeologicalArizona Geological Survey. The workslh0J" concltsions are summarized in USGSzona's Industrial Rock and Mineral Re<lOUI'Cesc'shop Proceedings. Copies are avalla[)le IU,.,from the Books and Open-.FUeUSGS, Federal Cel~telr,B"x "~54;!5,I)el1

Theses and Dissertations, 1989The following list includes theses and

dissertations on Arizona geology, geologi­cal engineering, hydrology, and relatedsubjects that were awarded in 1989 byArizona State University, Northern Ari­zona University, and the University ofArizona. This list, however, is not a com­plete compilation of theses on such topics.Theses on the geology of other States thatwere awarded bythese universities are notlisted, nor are theses on the geology ofArizona that were awarded byout-of-Stateuniversities.

Most theses included here are not avail­able in the libraryofthe Arizona GeologicalSurvey. Each thesis, however, may beexamined at the main library of the univer­sity that awarded it. Information may alsobe obtained from the respective depart­ments, which are indicated in parenthesesafter each citation according to the codeslisted below.

Arizona State University, Tempe, AZ 85287;(602) 965-9011. (Gg-Geography; GI-Ge­ology)

Northern Arizona University, Flagstaff, AZ86011; (602) 523-9011. (G-Geology)

University of Arizona, Tucson, AZ 85721;(602) 621-2211. (CE-Civil Engineeringand Engineering Mechanics; G-Geosci­ences; MGE-Mining and Geological En­gineering; MSE-Materials Science andEngineering; RNR-Renewable NaturalResources; SWS-Soil and Water Science)

Arizona State University

Archer, Bradford, Quaternary fossil tor­toises ofthe Phoenixbasin: M.S. thesis,174 p. (Gl)

Doorn, P.K, Geologic and gravimetric in­vestigations of the Carefree basin, Mari­copaCounty,Arizona: M.S. thesis, 307p. (Gl)

Drosendahl, J.K, Environmental geologyofthe Rio Salado development district,eastern part, Maricopa County, Ari­zona: M.S. thesis, 122 p. (Gl)

Gjoen, BRS., Formation of micrite and sparitefrom the breakdown of algae in apedogenic environment: M.S. thesis,92 p. (Gl)

Harrison, DH., A structural and petro­graphic analysis of two large intersect­ing shear zones west of Prescott, Ari­zona: M.S. thesis, 110 p. (Gl)

Haschenburger,Judith,Variation ofcopperin stream sediment: M.S. thesis, 67 p.(Gg)

Lee, S.E., The effect of Glen Canyon Darn onthe Colorado River, Grand Canyon,Arizona: M.S. thesis, 108 p. (Gg)

Matheney, RK, Oxygen isotopic investiga­tions in stepwise fluorination of hy­drous silica and other geologic materi­als: Ph.D. dissertation, 136 p. (GI)

Arizona Geology, vol. 20, no. 2, Summer 1990

Paul, T.A., Environmental rheology andmicrostructures of kyanite deformednear the sillimanite boundary: M.S.thesis, 96 p. (Gl)

Northern Arizona University

Conway, F:M;, Volcanology, geochemistry,and petrology of the west-centralMormon Mountain volcanic field, north­ern Arizona: M.S. thesis, 147 p. (G)

Cook, M.J., Depositional and architecturalanalysis of the lower massive sand­stone (Triassic Moenkopi Formation)of north-central Arizona: M.S. thesis,141 p. (G)

Darr, M.J., Hydrogeology of the Oak Creekarea, Verde Valley, Arizona: M.S. thesis,268 p. (G)

Grover, P.W., Stratigraphy and depositionalenvironment of the Surprise CanyonFormation, an Upper Mississippiancarbonate-clastic estuarine deposit,Grand Canyon, Arizona: M.S. thesis,303 p. (G)

Harwood, RD., Onder cone breaching eventsat Strawberryand O'Neill Craters, SanFrancisco volcanic field, Arizona: M.S.thesis, 104 p. (G)

Lindholm, M.S., Volcanology, petrology,and structural geology of Proterozoicmetavolcanic rocks in Mescal Canyon,Jerome,Arizona: M.S. thesis, 153p. (G)

McCormack, D.e., The geology ofWupatkiNational Monument, northern Arizona:M.s. thesis, 97 p. (G)

Sanders, e.M., Stratigraphy, sedimentol­ogy, and paleogeographic significanceof the sedimentary portion of the Ter­tiary Hickey Formation, central Ari­zona: M.S. thesis, 143 p. (G)

University of Arizona

Ali, A.S., Reactions of urea phosphate incalcareous and alkaline soils; ammo­nia volatilization and effects on soilsodium and salinity: Ph.D. disserta­tion, 88 p. (SWS)

Brooks, M.W., Distribution and assessmentof expansive clay soils in the Tucsonbasin,Arizona: M.S. thesis, 150 p. (CE)

Cai, Wenlong, Application ofnetwork flowand zero-one programming to open­pit mine design problems: Ph.D. dis­sertation, 225 p. (MGE)

Evett, S.R, Field investigations of evapora­tion from a bare soil: Ph.D. disserta­tion, 426 p. (SWS)

Fink, J.B., Induced polarization: electrochem­istry, fractal geometry, and geohydro­logic applications: Ph.D. dissertation,370 p. (MGE)

Flack, Paul, A method for establishingbase­line soil loss rates on surfacemine sites:M.S. thesis, 45 p. (RNR)

Holbert, S.B., Development ofa geographicinformation system based hydrologicmodel for stormwater management andlanduse planning: M.L.A. thesis, 114p. (RNR)

Imam, Bisher, Evaluation of disaggrega­tion model in arid land stream flowgeneration: M.S. thesis, 90 p. (RNR)

Jemison, RL., Conditions that define a ri­parian zone in southeastern Arizona:Ph.D. dissertation, 62 p. (RNR)

Jeon, G.J., Innovative methods for long­term mineral forecasting: PhD. disser­tation, 299 p. (MGE)

Jones, J.W., IV, An examination of scale­dependent electrical resistivity mea­surements in Oracle Granite: PhD.dissertation, 250 p. (MGE)

Jones, M.G., Clay mineralogy and petrol­ogyof the Lower Cretaceous fine-grainedclastic rocks, southeastern Arizona: M.S.thesis, 148 p. (G)

Jung, Kwansue, The comparative sedimentprocesses in channel and overbank:M.S. thesis, 161 p. (CE)

Kidd, D.A., In situ testing ofGila Conglom­erate with application to probabilisticslope stability: M.S. thesis, 107 p. (CE)

Kim, KH., Classification of environmentalhydrologic behaviors in northeasternUnited States: M.S. thesis, 212 p. (RNR)

Lantz, D.G., A comparative analysis of fourrainfall-runoff models on a smallwatershed near Tucson, Arizona: M.S.thesis, 142 p. (RNR)

Levitt, D.G., The use of reflected middleinfrared and emitted thermal radia­tion in the remote sensing of soil watercontent: M.S. thesis, 131 p. (SWS)

Lien, B.K, Field measurement of soil sorp­tivity and hydraulic conductivity: M.S.thesis, 93 p. (SWS)

Lueck, e.e., Rational drainage design forthe desert Southwest: PhD. disserta­tion, 307 p. (CE)

Lyons, Timothy, Stratigraphy and deposi­tional environment ofthe Colina lime­stone (Lower Permian), southeasternArizona: M.S. thesis, 260 p. (G)

Macfarlane, RB., A field test for detectingcollapse susceptible soils: M.S. thesis,128 p. (CE)

Muller, Eugene, In situ measurement ofthecohesion of cemented alluvial soil: M.S.thesis, 86 p. (CE)

Nordby, B.G., Sedimenttransporteffects ondrop structure scour: M.S. thesis, 69 p.(CE)

Potochnik, A.R., Depositional style andtectonic implications of the MogollonRim Formation (Eocene), east-centralArizona: M.S. prepublication manu­script, 61 p. (G)

Risely, J.e., Predicting runoff and salinityintrusion using stochastic precipitationinputs: PhD. dissertation, 193 p. (RNR)

(continued on page 12)

11

PROFESSIONAL MEETINGS

.--------Arizona Geology-------,Vol. 20, No.2 Summer 1990

Arizona Geological Survey

Director & State Geologist: Larry D. FellowsEditor: Evelyn M. VandenDolderEditorial Assistant: Nancy SchmidtIllustrators: Peter F. Corrao, Sherry F. Garner

CONSERV90. Nationalwater-supplycon­ference, August 12-16, Phoenix, Ariz. Con­tact CONSERV 90, 6375 Riverside Dr., Dublin,OH 43017; tel: (614) 761-1711.

Taking the Arizona Groundwater Man­agement Act into the '90s. Symposium,September 6-7, Casa Grande, Ariz. ContactMary G. Wallace, Water Resources ResearchCenter, Geology Bldg., Rm. 318, UniversityofArizona, Tucson, AZ 85721;tel: (602) 621­7607.

The Colorado Plateau During the Meso­zoic Era. Symposium, September 29-30,Flagstaff, Ariz. Contact Mike Morales,Museum of Northern Arizona, Rt. 4, Box720, Flagstaff, AZ 86001; tel: (602) 774-5211.

National Colloquium on Professional Reg­istration for Geologists. Presented as partof the Association of Engineering Geolo­gists annual meeting, October 1-5, Pitts­burgh, Pa. Contact Robert E. Tepel, AEGCommittee on Professional Registration, 767Lemonwood Ct., San Jose, CA 95120.

(continued from page 10)tion might be seen as self-serving. Perhapsthe three R's will become the four R's: reading."riting," "rithmetic," and resources.

(8) Tax Holiday for Recapture of Capi­tal Investment. The least likely, but per­haps most effective, way to encourage exploration and new mine development inArizona is to do what British Columbia didfor many years: provide miners with a tax­free period, during which they could recap­ture their capital investment in new minedevelopment. This policy was very effec­tive, and any State that offered this miningincentive would almost certainly be ex­plored more actively.

Trying to predict a::onomic geology trendsin Arizona may not be realistic. A betterapproach might be for Arizona geologiststo decide where they want economic geol­ogy to go and then develop a strategy to getit there. Other exploration groups shouldbe asked what would attract them to Ari­zona in addition to a geologic environmentthat is favorable for discovery. This articlerepresents the perspective of an outsiderand I hope will encourage a more broadlybased discussion among members of thegeologic community.

References

Green, KC., 1989, A profile of undergraduates in thesciences: American Scientist, v. 77, p. 475-480.

Eldridge, C.S., Compston, W., Williams, I.S., Both,RA., Walshe, J.I.., and Ohmoto, H., 1988, Sulfurisotope variability in sediment-hosted massivesulfide deposits as determined using the ionAmicroprobe SHRIMP: I. An example from thl,.Rammelsberg orebody: Economic Geology, v.83, p. 443-449.

Governor Rose MoffordState of Arizona:

Rosales Dominguez, M.C., Micropaleontol­ogyand paleogeography of the UpperMural Limestone of southeastern Ari­zona and northern Sonora: M.S. thesis,61 p. (G)

Sanchez-Corrales, V.M., Electrochemicalleaching of gold-bearing arsenopyritein alkaline cyanide solutions: Ph.D.dissertation, 150 p. (MSE)

Shafer, D.S., The timing oflate Quaternarymonsoon precipitation maxima in thesouthwest United States: Ph.D. disser­tation, 234 p. (G)

Smith, C.H., Compressional deformationand peraluminous plutonism in theLittle Rincon Mountains, southeasternArizona; a component of the fabric ofthe Rincon metamorphic core complex:M.S. prepublication manuscript, 54 p.(G)

Suliman, A.S.A., Spectral and spatial vari­abilityofthe soils on the Maricopa Ag­ricultural Center, Arizona: Ph.D. dis­sertation, 210 p. (SWS)

Thomas, S.J., Forward modeling and dataacquisition for high-accuracy electro­magnetic subsurface imaging: M.S.thesis, 203 p. (MGE)

Virdis, M.R., U.S. smelter acid sales andrevenues; the implications of adoptingEuropean acid trade and marketingpractices: M.S. thesis, 174 p. (MGE)

Walsh, J.L., The Hellhole Conglomerate; astudy of a mid-Tertiary extensionalbasin: M.S. thesis, 57 p. (G)

Wilkosz, M.E., River and wetland conser­vation and preservation issues in Ari­zona; a studyofagenda building: M.S.thesis, 193 p. (RNR)

Arizona Geological Survey845 N. Park Ave., Suite 100Tucson, AZ 85719

ADDRESS CORRECTION REQUESTED