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t ie / . , . i . . 'area soutfi Marievale HLne, -Rtiere the % la-Elrd a tra ta and
th e dyke ttave been retoOveg tiy- QrosLon.
fccttor^ing to E llis (3), the fracture occupied by tbe. iatru slo n »as salsly tbe. resu lt or internal tension due to ' suutetranestt subsidence. There Bre m si cat leas however that tbe coarse of tbe dyke ®as deterained to some extent by pre-..
ex lstlog trse tiires or fau lts. This is suggested by Us frequent cbanges of direction and elso by tbe S e t tbat tbe ayke, where t t transgresses tbe Main Beet Leader, frequently , 8 t$ s inwards,towards the downtbrown side. A teniiqa fraetig-e,due -to v e rtlo sl stresses t?oald have to dip outwards,.towards tbe Upttircmn side. In tbe nortihern/of toe "Old IM y * , t i SBTtflgs \. end Daggafanteln .Mines, there is Horizontal separation o t tbe. . "reef% on tbe: dyKe on tbe eastern Side, and overlapping pti tbe.. .western am* souttiem sides, m e racks inside the dome W e , ,v not only dropped vertically but have moved ttonaaftteUy -to a s iu tb -neste ti? a lrestlon , as would be easetie? I t tte aanten ■ ■
* r U , D,direocioas oetweeo «est =04 so itii. mgi M U lasja tea tin s
point.n * u » . , W 4 i t r T . '
tee "OM ladr” tod tw Se« S tats Areas lotrosloo are im gb li i;
i . w « i n . w 9 0 .
. u w .* u w . f m i « , w m w " " 1 * « ^ * "
K U t w w fo r"
m tl0re6=l=s ’rar / m e j
They a t» ao t confined to any p a p tlc a ia r area and are tiuch tb ioner
; tbao .the upper s i l l phase' o f th e "Old Lady". Generally they
... s r e com pletely decomposed. . ,
Tffo examples air6 fcnown .underground of in tersec tio n s
. between narrow decoeposeS dykes, believed to be qu artz diabase, *
and normal sad reversed f a u lts devoid of igneous m ateria l, l a .'
bo th cases th e dykes are younger than tbe f a u lts an0 are net.: ■
d isp la ce s by them. TDls shows th a t the s t r a t a were frac tu red •
and fa u lte d before th e quartz diabase dykes and s i l l s were
in truded , Tbe,dykes fo llo ^ p re - e x is t in g planes- m. f ra c tu re or
f a u lt in g and in most cases suffered a g rea t d ea l-o f .shearing ;
ttsrougti renewed aovement on the fra c tu re s a t a l a t e r period* . .
g. PETROLOGY . ■/.-.> >
Quartz diabase is a tough, pale grey, fine-grained rock,
with a d u l l , non-lustrous appearance s im ila r to ilo e n ite ats&asev
In th in dykes and s i l l s and near tb e margins of th ick er in tro s -A
ions i t i s u sually sheared and completely decomposed. «ben sheared i t i s d i f f i c u l t to d is tin g u ish in hand-specimec frm - ,;,.
occasional specimens from the centres of th ic k in trusions ;
at,™ an o p h ttlc texture. » th in s e c tio n t t l g . IS ) , file
' -i r m f t * . y ;
w a .
m i w r r aK n o j; " W " ./ largely.-
r " i
Qpartz Diabase from centre of "Old Lady" Dyke, E ast Oagga- footelQ Mine. Ordinary l ig h t. M agnification X21.
P la g io clase , s a u ssu rltlse d (pale grey la th s )Remnants o f long prism atic c ry s ta ls o f A uglte, enclosing P lag io clase la th s (darker grey, in d is t in c t)
This specimen is unusually coarse and fre sh . O pbttlc textu re Is c le a r ly v is ib le .
Quartz Diabase from "Old Lady" Dyke, Springs Mine.
Q iartz Diabase from "Old Lady" Dyke, Daggafonteln
Ordinary l l g b t . M agnification X19.No tra c e o f primary te x tu re .
O ra llte (sm all pale bladed c ry s ta ls ) C h lo rite , C a lc lte , Leucoxene e tc . (grey , in d is t in c t)Iron Ores (black)Q iartz (c le a r )
In f i g . 17 a v e ln le t o f q u artz , ep ldote and c a lc lte crosses centre of f i e ld .
U /
larg e ly altered to uralifr
Typical quartz diabase
decomposed than the specii
o p n ltlc texture are s t i l l (
renaln :xcept possibly qu
and occurs in thin bladed ,
the rock a characteristic
scope. Iron ores occur
occurs In minute clear pot
A lb lte is sometimes consp
snowing cneracterlstic li
z o l s i t e , ca lc lte , ru^ lle , <
p re sen t.
Frequently the rock >
( f ig . 17), I t consists i
iro n ores, quartz, calctti
o f a primary texture. M
epldote and ca lclte are f
tn e re are occasional rell*
tiOT.ewr the rock is sSiean
destroyed.Egsential Minet
Plagioclase - * ptienoer 6056 An I or compi replace
la rg e ljF .a ite rea to u f a l t t e and c b lt ir t te . ■ . ' .
: ’ESptcel fitaBase i s f in e r in g ra in end atmft more -aecdopdseti tfean th e specimen sbown In f ig . 15. R elios o f
o p b it ie te x tu re a re s t i l l v ts itile but no p ris is tf stijierals / , ; •
. recdaia ax&ept posaibly Quartz, ( t i g , 15), u r a l i t e i s abunaaot and acdiira 1b th in blasefl c ry s ta ls and long f in e needles, .giving
tb e rock- a tiia ra tt^ ris tic ^ irea ttie ry 11 appearance under tbe •jntct'o-
scope. ' Iron Ores, oceur In sm all g ra in s and spebfcg. Quartz • : .
occurs i e minute e le a r pools ana occasionally as m .lcropegaatlte,-•
A lb lte is. sometimes, conspicuous a s sm all sca tte red c ry s ta ls k shoeing c h a ra c te r is t ic lam ellar tw in n in g .. A l i t t l e ep ldo te , : . v-
z o i s i t e , c a lc l te , r a t l i e , p y r i te ana p y r r h o tl te :8re oeeasionai^y
present.. '
F requently th e rock i s in a very advanced s t a t s o f alterMtlo9% ( f ig . 17), i t co n s is ts of a contused mass rif u r a i l t e , c h id r i te ,- ; '
I ro n o re s , q u ar ts , c a lc l te and o th e r m inera ls, f l th o u t any-tratid •
o f a Brimary te x tu re . Minute v e in le ts ol' o a lo r i te , quartz ,
ep iao te and c a lc l te are f a ir ly ebomoc. Sear in tru s iv e eontacts ...
th e re are occasional re lic s of a p o rp h y ritic -texture., GenersCLtx
boisever th e rock i s sheared .and a l l i t s primary fe a tu re s are .
d e s tro y e d .' ' '
S o l An ta n d e sin e -M ira d d n te ) . gaussu rltlsetv o r completely decomposed, occasionally - replaced by a lb l te .
fptiene a f te r llm e n lte ,
- " • S S J S i w S S ® ^
^ - . 3 3 %
j * =/s im ila r
■.. SLU enas I>°
'iRe. wQl:d tn tru d ed .e itti^ r before a r a f ts r , but - %
not W in g , tBe ^ ^ s W v O f the 'vec tersdors .lavas, since th# :
magna fitd' ttot reaob ib e . s a r fsc e (3 ) . Tbe magma s tiH d if lea ;.
near t to -g u rfa s e anfiyMOti g re a t depth, since, tbe diabase, i s :.
s im ila r , a p a rt tji# absence o r a m y g a e le a to tb e lavas Of .
tbe Teiitersiloi'p^ ■ th e Bird S e rie s . The bigbest
stra ^ lg ^ 6iBt$l5 . tioriaon•.reabhed by the "Old Lady" Is the
Kimberley .S tiale | :n6t f a r beL .. tb e pre-Ventersfiorp .surface but a c o ^ i s e r a m -dsptb belo s tfte top of tbe- Yectersdorp
% stem . Qiiarta diabase dykes and s i l l s ibtrtifle tb e lower Blsburg beds bu t are not known to penetrate th e Ven#ters&>r$>
lav a s. 4 .x-The above evidence poin ts to th e q uarta diabase in th is ions
being o lfler tbao th e VentersdorB la v a s , th e i r age bAlng ea riy ;
Ventersdorp or la te witwatersrand.
S e le s i s s siuBEary o f th e pltncsteal c h a ra c te r is tic s o r tbe f lv e g ra ip s o f In tru s iv e rocks described above*
V e rtle a l dykes trend ing Ntr-SE to B-w.
S i l l s a t o r n ea r p resent su rface .
Ho v e r t ic a l displacement o f s t r a t a on £
Fresh d a rk b o lo c ry s ta llln e ro c is .
Texture o p b ltlc to aub-opb ltlc .
Margins c h il le d , w ith p o rp b y rltlc texture*
E sse n tia l m inera ls; p lag ioclase (jpradorlte-by tow nlte),
a u g lte (d lo p s td lc ).
A ccessories: o liv in e (conspicuous In s i l l s , ra re in dykes),
iro n o res , b to t l t e , quartz ( in 6ykes, absent in s i l l s ) .
A lte ra tio n
Very l i t t l e . P lag ioclase and au g lte generally fresh*
O livine serp en tln lse d .
4saL ate Karroo.
Type o f In tru s io n .S i l l s In tb e Transvaal dolomite.A few narrow Inclined dykes in th e ffltwetersrand System;
K o lo cry sta llln e rocks, dark o r m ottled (Green Syenite) and/p a le
W /(Lie redaiab (Bed syeaite).T exture bypidtosbtpbie-granulBr (g ran ito id ) .t a r g lo s e M lise , p o rp b y rltic .E sse n tia l M lnersla.
(a ) Green Syenite: p lag ioclase (andesine, la rg e ly
a l te re d to a l b l t e ) , a u g lte , u r a l i t e ( a f te r aug lte)
(u) Bed S yenite: a lb l te (90# o f rocic).
A ccessories.
(a ) Green S yenite: iron o res , q u artz , b lo t l te .(B) Red Syenite: b lo t l t e , quartz (much micropeg-
m a tlte ) , iron o res .
A lte ra tio n
(a ) Green sy en ite .Moderate to In tense . Andesine a lte re d to a lb l te , aug lte
to u r a l i t e and e b lo r i te . Secondary ep ldo te, quartz
and c a lc l te .
(b j Bed S yenite .Moderate, A lb lte cloudy, b lo t l t e cb lo ritlsed *
M sPre-Karroo. Bushveld o r post-Watertergr.
I r r e g u la r v e r tic a l dykes trending NB-SW.
Rnpw s i l l s and narrow in clin ed dykes.
l i t t l e v e r tic a l displacement o f s t r a t a on dykes.
D un grey a lte re d rock, f in e t o medium grained.
| 76Ifexture o p b itlc ( r e l i c s ) .
M argins e b ll le d anfl deccmposefi, occasionally shearmii
E sse n tia l m inerals: p ieg ioclase (andesine-labradorLte, decomposed), u r a l i t e ( a f te r a u g lte ) .
A ccessories: Ilmen t t e , quartz?, various secondary m inerals.. A lte ra tio n
in tense* P lag io clase rep laces by c h lo r i te and o ther min
e r a ls . Auglte o ra ll t la e d . Ilm enlte leucoxenlsedi
Secondary ep ldo te, q u artz , a lb l te , c a lc l te , t a lc .
£ggPre~Transvaal, post^Ventersdorp.
4 . THE mRITE-msANOPKYRE
Troe o f In tru s io nTblcjt s i l l s of n o rl te overla in by granophyre. In the
Kimberley Shale, Bird G&iartzlte and Jeppestosn Series*
T ransgress ive dyte phase d isp lac in g the Maln-Blrd s t r a ta
v e r tic a l ly atitait 300 f e e t .
A few narrow dykes and s i l l s .
P e tro lo g ic a l Features
(a ) B o rlte .D ull greenlsb-grey rock, medium to coarse grained.
T exture hypldiontorphic to panldltXQOz*pl5ic.
M argins c h il le d .e s s e n tia l m inera ls: e n s ta t l te and d lopslde (a lte red to
serp en tin e and u r a l i t e ) .A ccessories: p lag ioclase (by tow nlte-anortb lte , decoo-
posed), quartz ( l i t t l e mlcropegmaUte).
: : -(tf) Gr^flOJ&yre.
t t t t l s fe y rodk, medium to coarse grained.Texture g ra n itic*
Contact e l t t t sbale g ra d a tio n a l, con tac t w ith q u a r tz lte
Sbaitier.E s se n tia l m inera ls: o rthoclese (deccxnposad), q uarts (cucb
m lcropegmattte), hornblende.
A ccessories: i la e n l te , e b lo r i te .
A lte ra tio n
(a ) N o rlte .In ten se . Pyroxenes a l te re d t b serpen tine and u r a l l t e t
P lag ioclase decomposed.
(b) Granophyre.In ten se . O rthoclase s e r le l t l s e d , hornblende e b lo r i t ls e d ,
Ilm en lte leucoxenised. Secondary c a lc l te and occas- ■
lonal ep iao te .
MSS.L ate Ventersdorp.
Thick s i l l s in tb e B ird S eries and Jeppestosn S e rie s , a i tb
tran sg ressiv e dyke phase forming a closed rin g sM
d isp la c in g the s t r a t a v e r tic a l ly abcait 850 f e e t (the
"Old Lady").Numerous th in n er s i l l s and inc lined dykes w ith no p a r t ic
u la r tre n d , d isp lacing th e s t r a t a v e r tic a lly ,
D ull grey a lte re d rock , f in e g ra in ed .
: dpblttd . toccBsiooal r e l t c s ) .
M argins sheared and decomposed»
S M en titi . m tnara lst p lag io cla se (andesine-labrB dorlte ,
6ec<a®oseS), u r a l i t e ( a f t e r a u g lte ) .
A ccessories: Iron o re s , q uartz ( l i t t l e m lcroBegnatlte),
various secondary minerals*
A lte ra tio nExtreme. B enerally no- p rlsa ry te x tu re . P lag ioclase toeomr
posed aM seldom recogn isab le. .4 4 Augite u ra il t l s e d i :
Secondary e b lo r i te , q u artz , ep ldo te , z o l s i t e , a ib ltS
c a lc l te , leucoxene, tu tU e .
a s sE arly V entersdorp o r L ate W ltwatersrand.
My thanks are fitie to D r,J.A .Bancroft, Cohsuitlng Geologist,
Aaglo-*fi6riean corporation o f Scutb A frica L td ., f o r Bermlaalyf
t o w r ite t h i s tb e s ts .
1 am u y eb te d t o o ther members, p a s t and presen t, o f the
s t a f f o f tb e Anglo-American Geological Laboratory, sp rin g s , fo r
moat o f tb e underground geologica l mapping on whicb th i s fiorSt
I s based, ana f o r tb e prepara tion o f most o f th e tb ln 's e c tio n s
I examined;I thank Dr.B.B.Broek, A ssis tan t Constiltlng G eologist, fo r
b i s in te re s t and c r it ic ism s , Mr.H.C.H.Ubltesiae and Mr.P^i.
Stiydom f o r many h elp fu l suggestions in the course o f th e woM*; and !£r.C.S.Beugger fo r advice In drawing th e plans and sections*
Springs, T ransvaal.
BOth Novea&er 1949.
G > * r r * l . «.W.: o f rM n M m T . ^
L M .. M0Q.(2 ) m m t , A .L .: - I t e aw ftcor s m th * m o a * . c a i w m a
B oja , 1939.
(3) sails, J .: "M ratmal"” °* * « « ' Mertto “« w * r — » — . W M i " . M ' » * '
VOL. s a i l . 1S40- „ ,
S o c .s . i . , m i . m n , I S « . ' ' "•
- - : = = = - = -
t r a n s . s e o l^ o c .s u i . . Vol. Z O . l94S- •
$ rans .s«< il.soc .s .A ., Vol* l * 19to-
1
:
i - I / t i t 5 £ S 3 5 t W l - F i c H g
" ' i r V 'v t W v - : ••
i .
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■■■■ "■ >
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f: li i" f. 1 ' il* i k L M i M'S4: 'k
f
&
P L A T E M E
P O S S I B L E STRAIN RELATIONSHIPBETWEEN THE 1 LMEN ITE DIABASE
DYKES AND OTHER STRUCTURESS C A L E I : I 0 0 , 0 0 0
S E C T I O N O F
S T R A I N E L L I P S OI D R E F E R E N C E
A X E S O F F O L D I N G I N T H E M A I N R E E F L E A D E R
— - A n t i c l t v n
T E A R F AULTS
RttjVvC- Ko-hviieol —. . . . . . . L « f t -
I U M E N I T E D I A B A S E D Y K E S
\ /
Vo,
S C A L EVrko*s«n. «l3 Of f e « t )
3 0
' r .
PLATE YUS E C T I O N O F N O R I T E - G R A N O P H Y R E
A N D "OLD LADY' HNTRUSIONSS C A L E I : 5 0 , 0 0 0
KARAOO
T n x r u r z z a . ul u a zz
S C A L E( T h o u s a n d s of f e e t )
R E F E R E N C E
W IT WA T E R S ft A N D S Y S T E M
V77T777J K i m b e r l e y S h a l e
rv v v v d B i> "d A m y g d o lo ic l
KXWWvS Te.ppeb^-iwn Series
1 N T R US I V E S
( M o n t e - G r a n o p h y r e
Q- ua r bz D i a b a s e
£. D
».g<
x N-W
SK
=^t
P L AT E 3ZE
PLAN OF NORITE - GRANOPHYRE AND"OLD L A D Y ' INTRUSIONS
S C A L E I : 100 ,00 0
R E F E R £ N C E
D Y K E S DI SPL ACI NG THE MAIN RE EF LEADER
fv Jo rL C ft - G r o vi o p K y v a.
O l A U»oLij’' ( c^K arka d. L a b a 9 « -) •
S I LLS IN T H E B I R D S E R I E S OR T H E KI MB E R L E Y S HAL E
X * x x N e v i t* . - G r * « .o p k - j r c .
F A U L T S D I S P L A C I N G T H E M A I N H E E F L E A D E R
&-—g--------- N o r m a l
=----; ---------- ReV «.y54.el
. - 0 -------- T e a r
--------------------------L I N E OF S E C T I O N I N P L A T E VTT
L : . . I ' L ' ' ' j i , 1' h . I I
P L A T E m C
P O S S I B L E STRAIN RELATIONSHIP BETW EEN THE I LMEN ITE DIABASE
DYKES AND OTHER STRUCTURESS C A L E I : I 0 0 , 0 0 0
R E F E R E N C E
A X E S OF F O L D I N G I N T H E M A I N R E E F L.« A P E R
— | r — S y n- c l i ni xl -------- ^----Ah. t i t . l i . r - . al
T E A R F AULTS
........ L e f t - tvo.>t.cle.cL
I L M E N I T E D I A B A S E D Y K E S
S C A L E(JU < m s* n ..L s o f f e e t )
3 0
PLATE YUS E C T I O N O F N O R I T E - G R A N O P H Y R E
A N D "OLD LADY' HNTRUSIONSS C A L E f ; 5 0 , 0 0 0
g g a a g a Z k Z > Z % Z Z Z : ^ 2 Z ^ Z Z 7 Z X 2 Z ? Z X Z Z 7 2 ^ K x ^
R D S e r i e s ^<<V n n
; W ^ ^ X \ X \ x x x ^ s X t
R E F E R E N C E
S C A L E ( T h o u s a n d s of f e e t )
W I T W A T E R S R A N D S Y S T E M
77777772 K i m b e r l e y S h a l e
rv v v v a B i r d A m y g d a l o i d
K^VvYnX^ Te . p p e s t o w n Se r ve
t N T R US I V ES
N o r t t e - G r a n o p h y r e
Q- ua r b z D i a b a s e
T
_JN.
Lr
NEV STATE AREAS f NTR usi ON
PL AT E mPLAN OF NOR IT E-GRAN OPHYR E A N D
"OLD LADY" INTRUSIONSS C A U £ \ •, ioo^ooo
R E F E R E N C E
D Y K E S D I S P L A C I N G T H E MAI N R E E F L E A D E R
3a®&aB^^8SS5B N oi-C t* - G rA T io p k g y *
"OIA. L a <i y '* ( c L t a b a S e . )
S I L L S I N T H E B I RT> S E R I E S OR T H E KI MB E R L E Y S H A L E
V X X X N o v 'l t - G Y fcH.O p k ^ r c.
C?i*a»-Ca eLLttbixae.
F A U L -’" ' - D I S P L A C I N G T H E M A I N %EEF L E A D E R
± T----------- Noiri tvt t .1
—~ — j---------- R c v e r s A e l
^ --------- T e a - v
------------------------- L I N E OF S E C T I O N I N P L A T 't7XE
2 . 5 0
O L D . L A D Y
S C A LE
Author Brandt R TName of thesis The Geology Of Certain Igneous Intrusive Rocks In The Far East Rand, Transvaal, South Africa.
PUBLISHER:University of the Witwatersrand, Johannesburg ©2013
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