AT THE UNIVERSITY OF NEW MEXICO \

A ST1W OF S I L I C I C PLUTONIC ROCKS IN THE ZUNI AND FLORIDA MOUNTAIFfS TO EVALUATE THE POSSIBLE OCCURRENCE OF

GISSENINATED !!RANIUP? AND THORIUR DEPOSITS

URANIUM AND THORIUM ABUNDANCES AND WHOLE ROCK CHEMISTRY

PRELIMINARY STUDY OF THE FLORIDA MOUNTAINS, NEW MEXICO:

NMEI REPORT NO, 77-1104C

DECEMBER 1978

This research was conducted with the support of the New Xexico Energy and Minerals Department (EMD). and the New Kexico Energy I n s t i t u t e a t The University of New Mexico ( N M E I a t UNM) under Contract 77-1104. However, any opin- ions, f indings, conclusions, or recommendations expressed within this report are those of the authors and do not necessar i ly re f lec t the views of the EMD o r of the NMEI a t UNM.

NMEI Report No. 77-1104C

i

A STUDY OF SILICIC PLUTONIC ROCKS I N THE ZUNI AND FLORIDA

DISSEMINATED URANIUM AND THORIUM DEPOSITS MOUNTAINS TO EVALUTE THE POSSIBLE OCCURRENCE OF

Uranium and Thorium Abundances a n d ' 6 h e Rock Chemistry of the Florida Mountains, New Mexico:

Preliminary Study

Final Report

August. 15, 1977 - August 14, 1978

P r inc ipa l Inves t iga to r s

Douglas G. Brookins, Department of Geology, Universi ty of New Mexico

Chris topher E. Rautman, New Mexico Bureau of Mines and Mineral Resources

L. LeRoy Corbitt, Department of Geology, Eastern New Mexico Univers i ty

Authors

Douglas G. Brookins, Department of Geology, Universi ty of New Mexico

Chris topher E. Rautman, New Mexico Bureau of Mines and Mineral Resources

L. LeRoy Corbitt, Department of Geology,'Eastern New Mexico Universi ty

NMEI #77-1104C

December 1978

1

Uranium and Thorium Abundances and Whole Rock Chemistry of the Florida

Mountains, New Mexico: Preliminary Study

Douglas G. Brookins, Department of Geology, University of New Mexico

Christopher E. Rautman, N.M. Bur. Mi.nes.Min. Res.

L. LeRoy Corbitt, Department of Geology, Eastern New Mexico University

abstract

The uranium and thorium abundances in the Precambrian granitic and of

the syenitic rocks (age unknown) of the Florida Mountains have been .

analyzed by delayed neutron activation analysis. The average uranium

content of 90 surface and drill core samples is 3.12 ppm and thorium content

for 66 samples is 12.33; Th/U = 3.97, well within the normal range for

granitic rocks (3.7 - 4.2). Although the Th/U ratio is normal for granitic

and syenitic rocks, a negative correlation between uranium (and Th/U)

with A1203, K20, and (K 0 f Na20) is observed. This-may be due to (a) der-

ivation. of the syenitic rocks from parent, low uranium. gabbroic rocks o r

(b) uranium loss during weathering. For the latter, significant amounts

2

of uranium may have been removed and possibly not transported far from the

source area. The syenitic rocks do not possess high uranium contents

typical of other areas.

L

Introduction

The Florida Mountains, south-central New Mexico are of interest because

of the presence of syenitic rocks (Corbitt, 1971) and the assumed association

of uranium enrichment with uranium. This assumption prompted part of this

study, vi?.. to determine if the rocks of the Florida Mountains were indeed

uranium rich and, if so, whether they represented a possible, low grade

uranium resource. If uranium poor, then uranium loss may be postulated

which would indicate that uranium exploration in the surrounding sediments

may be justified.

The Florida Mountains are very complex geologically; syenites originally

mapped as Mesozoic by Corbitt (1971) have been indicated as much older

(i.e., from early Phanerozoic (?) to Precambrian; Brookins, 1974). Whole

rock chemical studies and petrographic studies have also been carried out

to help assess the relationship between the granitic rocks and those with

syenitic affinities. Some of this work is still in progress, and additional

age work is contemplated and essential to attempt any material balance

between the granites and syenites.

Uranium and Thorium Investigation

The uranium abundance in the Florida Mountains is of interest for

several reasons. First, the rocks in which one might logically expect

uranium enrichment, viz. syenites and quartz syenites, are depleted in

uranium and thorium and Th/U is also low. Secondly, syenites typically

show a positive correlation between potassium (or potassium plus sodium)

and uranium. In Figures 2 to 5 are plotted U VS. K20, U VS. A1203, Th/U vs.

A1203, and U VS. (Na20 + K20). In all cases uranium shows a negative

correlation with increasing alkali and alumina content. Despite scatter,

3

this holds true for surface samples as well as drill core samples. These

data may be interpreted in several ways, the two most obvious explanations

are: (1) The syenites were derived from an alkali gabbro parent with low

Th and U; this model is possible as hornblende gabbro, presumably gradational

into syenite, is noted in the northern Floridas by Corbitt (1971). (2) Uranium

has systematically been'lost due to weathering or other processes. If (2)

is correct, then, assuming normal U in the range of 4-5 ppm for granitic

to syenitic rocks, some one million tons of uranium m y (hypothetically)

have been released from just 100 km of rock. This in turn indicates that 3

either high uranium in stream sediments near the Floridas might result

or that small (?) uranium deposits may be found in some of the sedimentsf

sedimentary rocks nearby. Critical to evaluating (1) versus (2) is the

exact age relationship between the granites and syenites; Brookins (1974)

has suggested that the syenites are not coeval with the granites, but how

much younger has not been resolved. This problem needs much more detailed

work.

The Th/U ratio for the Florida samples is shown as Figure 6 ; despite . the positive correlation, deviation from ThfU = 4 is apparent. The U and

Ti correlation is tested in Figure 7; a negative correlation between U

and Ti is indicated with Ti enriched in the U-depleted syenitic rocks.

Surface samples and dril1,core samples show the same trend. Collectively

these data hdicate, as mentioned earlier, that a systematic variation

between granitic and syenitic rocks exists. The problem of temporal

relationship between the two rocks remains unsolved.

Whole Rock Chemistry

The'whole rock chemistry for the Florida samples is presented in Table 2.

Although rocks mapped as syenites (FM-3, FM-4, F"7 (upper six samples), FM-8)

4

are justified based on petrography (See appendix), their Si0 contents

are slightly higher than normal syenites, a point made by Brookins (1974)

and Brookins and Corbitt (1974). High total alkalis and alumina support

classification as syenites. Those rocks identified as granites possess

Si02 contents from 71-77 percent and are characterized by lower alumina,

total alkalies, titania. Iron is not systematically distributed between

the various rocks although it is. fairly constant for any one drill hole

thus suggesting relatively little iron loss.

2

The.whole rock chemical data will be more carefully interpreted when

trace element data are available and additional Rb-Sr studies have been

completed.

Acknowledgments

Partial financial support was provided by the N.M. Energy Resources

Board (Grant #77-1104). The N.M. Bur. Mines and Min. Resources provided

assistance in the drilling and in the x-ray fluorescence spectrography.

R. T. Hicks, K. T. Emanuel and R. S. Della Valle of the University of

New Mexico assisted in the work. The facilities of P-2 and CNC-11 at

the Los Alamos Scientific Laboratory were used for the uranium and thorium

analyses by delayed neutron activation analysis; acknowledgment is due

M. Bunker and J. P. Balagna.

5

REFERENCES CITETI

Brookins, D. G., 1974, Radiometric Age Determinations from the Florida

Mountains, New Mexico: Geology, v..2, p. 555-557.

Brookins, D. G., and Corbitt, L. L., 1974, Preliminary Rb-Sr Study of

Igneous Rocks of the Florida Mountains, New Mexico: EOS Trans. Am. Geophys. Un., V. 55, p. 470-471.

Corbitt, L. L., 1971, Structure and Stratigraphy of the Florida Mountains,

New Mexico: Unpub. Ph. D. Thesis, Univ. Xew Mexico, 115 p.

Sample

FM5-1 FM5-3 FM5-5 FM2-1 FM7-3 FM8-1 FM2-2

FM7-4 FM7-2 FM2-4 FMl- 6 FM7-1 FM7-6 FM-11 FM7-8 FM8-2 FM2-8 FM7-5 FMl-3 FM7-5 FM4-1 FM5-6 FMl-2 FMl-7 FM2-5 FMl-5 FM4-4 FM4-2 FM4-3 “2

FM2-3 “4

TABLE 1

Th and U Data: Florida Mountains

Th (ppd U (ppd

13.65 3.08 35.8 7.80 15.0 3.65 16.4 4.03

. 2.40 1.58

12.9 , 2.88 15.0 2.80 3.70 2.39 3.63 1.77 18.2 4.81 17.4 3.03 3.15 1.42 30.8 7.08 18.6 3.89 4.26 1.83 17.1 3.69 18.4 4.22 3.69 1.65

, 24.6 5.44 13.0 2.76 7.26 1.87

19.8 4.18 23.1 4.56 12.9. 2.33 11.5 2.57 16.3 4.17 2.67 1.50

5.08 1.25

3.29 1.47 18.9 2.77 14.5 3.15 16.2 3.35

6

Th/U

4.43 4.59 4.11 4.07 1.52 4.48 5.36 1.55 2.05 3.78 5.74 2.22 4.35 4.78 2.33 4.63 4.36 2.24 4.52 4.71 3.88 4.74 5.07 5.54 4.47 3.91 1.78 4.06 2.24 6.82 4.54 4.84

-

7

TABLE 1 (continued)

Sample

F1183 F1184 F1185 F1187 F1188 F1189 F1190 F1191 F1192 F1193 F1194 F1195 F1196 F1197 F1198 F1199 F1200 F1201 SP 9m0, CDSWSElO .

GPSWSW97 SPE4 SPSW3 GPNE31 SPSENE26 SPSESE15 CDSWNW18 CDNW34 GPNwNw18 sPswsw26 GPNENE24 SPSWSW22

”

”

”

”

”

”

12.8 19.0 3.14 7.23 11.4 11.1 16.4 24.6 2.48 2.01 28.3 22.3 12.66 4.74

2.98 3.05 8.04 3.63 1.38, 5.53 1.53 1.48 7.73 3.44. 4.80 3.56 5.61 2.62 6.43 1.55 1.16 2.60 4.10 4.40 1.55 1.76 2.55 3.65 3.80 5.95 1.64 0.86 7.50 4.73 3.45 2.15

8

TABLE 1 (continued)

Sample , Th (ppm)

GPCNW31 2.33. GP nTw6 2.05 SPNWNE23 2.54 SPC4 14.49 SPWC19 7.69 SPNwNw25 19.1 SPSW36 "

GPCNE31 10.6 GPNE13 6.22 CENENElO I

CDsw3 "

GPSESEM "

SP9 + s m o 4.22 GPSESE14 9.33 SPSWSW36 1.95 CDNElO 15.98 SP9 4.67 CDCNE3 3.34 GPNESWlZ 23.8 GPNWNW24 18.1 GPNESW14 8.75 SPSSW3 6.08

NOTES : (1) FM samples from drill core (see Fig. 1) (2) F1183-1202 surface samples; see Brookins

u bpm) 1.66 1.48 2.02 4.02 2.86 3.07 3.63 2.36 1.68 2.69 1.77 0.65 1.37 3.58 1.55 3.20 1.25 1.40 3.33 3.95 1.86 1.22

(1974) (3) CD = Capitol Dome Quadrangle (Corbitt, 1971) ( 4 ) GP = Gym Peak Quadrangle (Corbitt, 1971) (5) SP = South Peak Quadrangle (Corbitt, 1971)

9

FMl-1

71.42

13.03 .35

4.83 .19

4.28 .34

99.38 4.94

FM2-1

77.42

11.68 .32

2.32 .18 .02

5.06 2.38

99.38

m-2

63.36

17.36 .24

6.10 .56

4.00 .44

97.83 5.77

FM5-2

73.50

12.27 .31

4.17 .19

3.80 .35

4.79 99.38

TABLE 2

Whole Rock Analyses -- Florida Mountains

m - 2

71.92

12.54 .29

5.02 .29

4.04 .42

99.22 4.70

FM2-2

76.85

11.19 .32

4.14 .14 nd

4.67 2.31

99.62

FM3-3

62.86

16.29 .35

7.61 .41 .45

4.32

97.95 5.66

FM5-3

70.10

12.38 .65

7.36 .32

3.74 .16

4.56 99.27

FM1-3

70.90

12.36 .26

6.66 .63

3.32 .37

4.62 99.12

m - 3

74.28

11.63 .40

5.30 .21 nd

2.47

99.39 5.10

FM4-1

61.85 1.08

16.52 5.18 1.15

6.80 2.11

100.48 5.79

FM5-4

73.54

12.61 .33

4.14 .16 .20

4.33

99.60 4.29

FMl-4

72.46

12.49 .28

5.02 .32

3.57 .35

4.77 99.26

FM2-4

76.76

11.05 .33

4.45 .13

2.26 nd

99.65 4.67

FM4-2

60.47 1.24

16.35 6.32 1.84 2.52

5.43 6.74

100.91

FM5-5

73.90

12.48 .27

3.71 .20 .24

4.11

99.44 4.53

FMl-5 71.42

12.56 .30

5.42 .61

3.61 .49

4.88 99.29

FM2-5

73.48

12.55 .48

4.54 .23

3.03 nd

5.21 99.52

FM4-3

59.78 1.39 16.67 6.57 1.81 2.40 7.20

101.33 5.51

FM5-6

75.20

11.80 .28

4.02 .13

3.86 .12

4.36 99.77

FMl-6 72.14

13.10 .30

3.98 .24

4.38 .40

99.42 4.88

m - 7

74 * 98 .40

12.26 4.69 .15

2.95 nd

100.59 5.16

FM4-4

61.15 1.14 17.12 5.54 1.66 1.90

,5.77 6.82

101.10

FM7-1

65.56 .69

18.96 1.03 .43 .48

6.65

100.38 6.58

FMl-7 71.10

12.63 .33

4.96 .47

4.10 .38

99.02 5.05

FM2-8

74.56

12.49 .52

3.83 .10

2.85 nd

99.76 5.41

FM4-5

60.88 1.30

16.99 6.06 1.79 1.69 6.89

101.44 5.84

FM7-2

64.56 .74

18.12 3.08

. .41 .32

6.66

100.18 6.29

"8

70.79

13.07 .30

4.42

.53

.49

5.15 4.12

98.87

FM3-1

64.58

15.80 .28

5.85 .56 .48

4.00

97.99 6.44

FM5-1

72.41 .31

13.20 3.98 .20

2.85 .30

5.04 98.29

FM7-3 65.14

18.58 1.47 .36

6.69 .53

6.74 100.31

.80 "

10

FM7-4

Si02 65.09 Ti02 A1203 18.06

.63

Fe203 2.44

CaO .49

Na20 .49

6.58

total 100.08

MgO

K20 6.30

FM7-5

64.66

18.24 .58

2.44

.41

.40

6.61

99.92 6.52

FM7-6

70.45

15.20 .26

2.59 .30 .17

5.14

99.55 5.44

m7-7

70.41

16.02 .30

1.32 .26

5.75 .21

5.53 99.80

FM7-8

63.77

17.42 .68

.43

6.45 .41

6.19 99.83

4.48

FM8-1 FM8-2

68.23 .32

67.94 .29

14.31 14.56 4.40 .24

4.00 .19

.58 .68 5.74 6.44 5.45 99.27 99.52

5.42

FLORIDA MOUNTAINS "c

8.

7-

6- 0 Y (u

.5-

4i

FLORIDA MOUNTAINS 12

KzO VS. U A A

A SURFACE SAMPLE -SYENITE

A SURFACE SAMPLE - GRANITE

DRILL HOLE CORE SYENITE

x DRILL H&E CORE GRANITE ”+

X A X

FIGURE: 2

19

18

17

I:

1

FLORIDA MOUNTAINS A1203 VS. U

'c. Y o 0 '

o e

1 I

\ 0

8

13

2 3 4

FIGURE 3

e

14

19 -

18-

I 7-

16-

i 3-

12.

I I.

FLORIDA MOUNTAINS

0 \ @

0 4

vs. Th/U

\: e

0

I3 i .t

0 nl 2 O 9 Y i II ,

A

7

FLORIDA MOUNTAINS' 15

(No20 + K201 vs. U

A SURFACE SAMPLE -SYENITE

A SURFACE SAMPLE-GRANITE

SYENITE

e GRANITE @ DRILL HOLE CORE

X DRILL HOLE CORE

A e

A

A A X X

A X

X ' x X x X X

X . x A xx

X A

X A X

A

X ' A

X X

.A

A

n

30

n

n E 20 n

IO

0

FLORIDA MOUNTAINS Th vs. U

e e

7' OI c

a e-' 8 e

17

I .4

I .... a

I .2

1‘ :d n

Y 0.9

c!? 0.8 0.7 0.6

0.5 0.4

0.3,

0.2,

0.

FLORIDA MOUNTAINS Ti02 vs.. U

A

0

a

x X P%xpx X xx X

A M A A

A

x

X A

A

18

r

Spec. No.

"1 -2 -3 -4 -5 -6 -7

FM2-1 -2

' -3 -4 -5 -6 -7 -a

FM3-1 -2

' -3 F M4-1

-2 -3 -4 -5

FM5-1 -2 -3 -4 -5 -6

FM7-1 -2 -3 -4 -5 -6 -7

-a

-a FM8-1

-2

FLORIDA MOUNTAINS

Sample Descriptions and SpecGen Status

Location . Depth

0- 5 5-10 10-15 15-20 .

' 20-25 25-30 30-40. 40-50

SE/NE/Se/13/26S/8W 0- 5

10-15. 5-10

15-20

25-30 30-35 35-40 '

20-25

0- 5 5-10 10-15 - ~.

0- 5 5-10 10-15 15-20 20-21 0- 5

10-15 5-10

15-20 20-25 25-30 0-10 10-20 20-30 30-35 35-40 40-45 45-50 50-55 0- 5 5-13

Map Unit

FLORIDA MOUNTAINS

Description and Location of Rocks

1. Orthoclase,Granite Sections 10, ll', 14 T. 25 S., R. 8 W. Capital Dome area.

i

2. Hornblende Perthite Syenite to Quartz Syenite Sections 25, 35, 36 T. 25 S., R. 8 W. NW Portions Sections 6, 18 T. .26 S., R. 7 W. Mostly nortii of major fault.

3. Per th i te Bio t i te Syeni te Section 25 T. 25 S., R. 8 W. Sections 30, 31 T. 25 S., R. 7 W. North of major fault.

4. Perthite Quartz Syenite Section 36 T. 25 S.; R. 8 W. Section 31 T. 25 S., R. 7 W. North of major f au l t .

5. Hornblende Pe r th i t e Granite Sections 25, 36 T. 25 S., R. 8 W. Section 31 'I. 25 S., R. 7 W. Sections 9, 10, 14 T. 26.S., R. 8 W. Section 18 T. 26 S., R. 7 W. Iden t i ca l to hornblende perthite syenite and per thi te syeni te except more quartz.

6 . Orthoclase Plagioclase Microcline Perthite Granite Sections 2 , 9, 10, 12, $3, 14, 15, 16, 23, 24 T. 26 S., R. 8 W. Sections 18, 1 9 T. 26 S., R. 7 W. South of major f au l t .

LOCATION

m4-3-

FM4-5- SPNW-25- SPNW-25"-

GPNWNW-6- SPNENE-35-

GPNWNWL8B GPCNW-6B-

GPSWNE-30- SPNENE-25-

GPCNE-3lA-

SPNWNE-23- SPSESE-23- SPCNE31B-

CDCNE31- SPSWSE31-

FM7-4-

FX7-6-

SPSW-36-

SPSWSE36-

FM8-2

SPNWNW25- SPSENE-26A- SP-SW-36(?)- GPNW-31A- SPSENE-14- GPSENE14

SP9+SW-lOA SP9i-SW-lOB s999w-10-

SPSENE26B- SPWNE-26-

SPNENE-35- SPSESE-26-

SPSW-36A- SPSESE-2- SPNE-2- SPNESE-4-

Brecciated

Hornblende It

11

It

I t

I1

I t

Biotite 11

It

Perthite I ,

11

I 1

11

Perthite

Perthite

Brecciated

Brecciated

Hornblende

I,

I,

I,

I,

11

11 .

1,

I,

I t

Perthite 11

1,

I,

I ,

I ,

I,

I t

Hornblende

Perthite I,

1,

11

11

11

I.

Perthite

11

Quartz 11

11

I,

11

Quartz

Plagioclase

Perthite

Perthite

Perthite

I1

I,

I1

11

11

1,

ROCK - Perthite

Quartz 1,

I,

I t

11

I1

I ,

Quartz 11

11

Syenite

11

I t

11

I t

Syenite

Quartz

Quartz

Orthoclase

Granite

71

I1

11

11

It

It

11

I.

11

(Cont.)

Quartz

Syenite II

11

11

11

11

1,

Syenite (calcito) I,

11

Syenite

Syenite

Quartz

(cent. )

LOCATION

SPE-4- SPCN-4 SPSW-3A- SPSW-3B- SPSSW-3- GPNwNw-18C- GPSESE-14C- GPNWSE-14- GPNENE-23-

GPESE 14 SPSWNW-16

FM 1-8

SPNESE 26- SP-SW?NW?-2- SPSW-3- - SPSN-3E- SPSW-3c-

SPSWSW9-

FM-3-

SP-SW-3D- SPSW-3-

SP9i-W-lOB-

SPSW16

FM5-2 FM5-6 CDNE-10

CDSWSE-10

GPNESW-12 GPSWSW-13

GPSESE-14B

GPCSE14 SPNWNW-14?

GPSWNE14 GPSWNW14 GPNESW14

Perthite. I,

11

11

(1

11

I,

11

11

1.

II

I.

Brecciated I f

11

11

I1

I,

Perthite

11

Orthoclase

Orthoclase

Orthoclase

Orthoclase It

11

.Granophyric

Perthite 11

Perthite

Perthite 11

I I

I ,

I ,

SPSESE-14-15 or R "

SPSE16D SPSE16B SPSE-45?

11

I ,

I ,

21

' ROCK -

11

Perthite 11

II

I t

I t

I1

Orthoclase

I,

Granite

Plagioclase

Perthfte

Granite ,I

I,

Granite

I!

11

11

11

11

Granite

11

Granite

Granite

(Calcite)

Orthoclase Granite

Plagioclase Granite I, ,I

Granite

Orthoclase Plagioclase 11 I,

11 I t

I1

11 I ,

rr 11 I1

11 I t

I , I,

It I,

LOCATION

SPSWSE15

GPNESE13

GPSW31B

FM2-8

SP99SWlOA

GPSESE14A

cDswsWl4 SPSESE14

SPSESE-15

SPSE16E

GPSwNw18

GPNWNW24

GPNENE24

GPSWSElOA

SP9SWlOA

GPNWNWl8A

SPSE45?

CDNWNE14

CDSWSWll CDSWll

GPSWSWl7?

GP-SWNE36

GP-SW3lA

SPSENW16 SPSWNE12 SPE17 SPSWSW22?

SPCNW6A

SPCNE34C?

Granophyric

Perthite

Granophyric

Granophyric

Perthite

Perthite

Orthoclase

Orthoclase

Granophyric

Microcline

Hornblende

Orthoclase

Orthoclase

Granophyric

Plagioclase

Orthoclase

Granophyric

Perthite

Orthoclase I1

Perthite

Orthoclase

Biotite

Perthite It

I,

I ,

Perthite

Biotite

Perthite

Orthoclase

Perthite

Perthite

Orthoclase

Orthoclase

Perthite

Perthite

Perthite

Perthite

Orthoclase

Plagioclase

Perthite

orthoclase

Orthoclase

Plagioclase

Perthite

Plagioclase

Granite

. .

II

Granite

Quartz

Orthoclase

Orthoclase I,

I1

I,

Orthoclase

Perthite

ROCK - Orthoclase Plagioc :lase

Microcline Plagioclase

Orthoclase Granite

Orthoclase Plagioclase

Quartz Granite

Grkite

Plagioclase Granite

Granite

Orthoclase Plagioclase

Granite

Plagioclase Granite

Granite

Granite

Granite

Granite'(Ca1cite)

Granite

Orthoclase Plagioclase

Granite

. ..

Syenite (Calcite)

Syenite

Quartz Syenite I, I,

I 1 I,

I1 ,I

Plagioclase Quartz

Orthoclase Syenite (Calcite)

22

Granite

Granite

Granite

Granite

Granite

Syenite