Geology of the Mwatate Quadrangle and the Vanadium Grossularite

Report No, 101

REPUBLIC OF KENYA

. , MINISTRYMINISTRY. . OF NATURAL RESOURCES

, GeolagicalGeological Survey ofof Kenya

GEOLOGY OF THE MWATATE # - I -;Y . QUADRANGLE AND THE .

' VANADlWVANADIUM M GROSSULARITE !:~

DEPUSrSDEPOSITS OF THE AREA ' . DEGREEDEGREE-SHEETSHEET 65 NE (SHEET 195/2.)195/2)

KENYA-AUSTRIAKENYA—AUSTRIA MINERAL EXPLORATION PROJECT 19751975-1978 -,I978 .*> . ,~ .? 8' ,;p-, .r #. ., .... , , ). ' ' 'I / ,' , - . .~>. - :I k.

Government of Kenya -' , .: 'Gommn'iGovernment,*;, ., -otof Awshi+tbf~&Austria throug + Ministry of Natural Rosour6o.s:Resources I I~.-:-it.- ?- + &qsfr~~~~.r!a~.~~.,s8Austrornineral Gesr'nbl-i.r&b.~1'

Mines and Geologicalical DeparDepartment trnmt' ,>; Pr.inzPrinz -Ewgsn-Eugen t.'9't~@q1+1~- StraBe 8-10 4- -' .., , ., ,. - -. ' ' " PO. Boxx 30009 Nairobi + ;t' . A-7d4.0,A~ 1040 w,0@Wien ;;.;JAL ,: , .*, .,:,y8 ' 2'. ' '. .,!.I.~.G,.' ,p cz.,~' ,,+?,. ' &&-+ . :- . A,. * . .?-(.4" : .. , .- B,qBy -; ;: : '~j..~ederma~GPhb W.PohlW Pohl PhD . G Niedermayr PhD ...... -. - ~ , . . /. . , .. . ~... '3' 8-:, Price:Price Sh.Sh, -—1979 IS79 C .. . . .: .. Geology(mulugx ofni'thc the MwatateMudmltvQumhxmglc Quadrangle (Sheet\hcct 19512)I‘)?‘ I and the{hr Vanadium Grossularite(jmwul‘nitc Depositsvmits of(ll-lilt‘ the Area-\1 v.1

(with coloured geological map)

by W. Pohl and G. Niebyr 1978

With\KHF a.1M»r';'_:'i't'w'i":1“:1'W. contribution on hydrogeology{Inuc‘ﬂu‘q by‘ 1. W. J.j. NautaT‘\.:1_;Eu.

Authors addresser: I Dr. Walter Pohl Dr. Gerhvd Niedamap 'I Department of Geology Museum of Natural History Mining University P. 0. Box 417 I A-8700 Leoben A-1014 Wien ; Austria Ada

Drs. Wde J...\' Nauta.J.‘ AUSTROMINERAL"\L‘NI'M )‘M‘d 4 3.1. Gea.V? .‘ m. b. H. dMinesm1. and‘ Geologiul‘ .' Dept.,my. P.Is 0.a» Box{MW 30009.‘ M M‘_r\g1;; Nairobi Kenya“VIM .‘. Table of Contents

Ab-act ...... 1.Introduaion ...... 1.1 Genenl ...... 1.2 Access ...... 1.3 Climate and Veget~tion...... 1.4 Phyaiopphy ...... 2. Previous gdogidwotk ...... 3. Summary of Geology ...... 4. Lithornatigraphy and Petrology ...... 4.1 Litbostratigraphy ...... 4.2 Petrology ...... 5.Strucrurcs...... 5.1 Foldr ...... 5.2 !-i"'Faults and Lineaments ...... 5.3 .J_Mtonga-Kore Chnrnockite Complex ...... 5.4 Tectonic Sicanceof the Ultrunafitee...... 5.5' N1".Minorstructures ...... 6.Met~morphirm...... 6.1 1".Progressive. Metamorphism ...... 6.2 Retrogressive Metamorphism ...... 6.3 Correlation of Mer~morphicand \Structural Hiatory ...... 7. Mindi|Depodts and Occurrences ...... 7.1'. rHGeneral...... 7.2 '-.--Interpretation of the Ammagnetic Data...... 7.3 Green Vanadium Grolsularite ...... 7.4 Red Corundum (Ruby) ...... 7.5 Other Coloured Gemstone...... 7.6 IndustrialMinuaL ...... 7.7 Ores ...... 7.8 Wat cr ...... 8.Refmnces ...... ; ...... FORBWORIJFINN-“(1RD

The ua covued by the Mw~ateQusdnagt tails within the Coastal opnl.- oar0n4 .., grLtpd- Ian4 the Nyikr, that have been for a long time the mpin sanctuary eS- wildlif~!II!-,

ia-:l southepsteroH: Kenya. The open plain is d@ed with a numha of hills and ridges1"" thu.Illlul.r‘|'.l\1:.- proaide,' thegcologkst 6 the only dpihatoump.

'C6eIlillL dkoveryI".- -.I".‘ of by corundummuth of thhnraa in eatly 1970spromptdr | inten-1.? 'l &a.xiw prcqeaing'.\I"I.-.-.;‘I;.,:|IIL &hin the area. ?'hi& retultad in tht dtsovay of durnI gmsptl._,;III.».I1 bite[IrIzc be-'. cue: known|-.II--..' lody ns green garnet or Ttnvolirc.

fie ocpu~nceof such a high clans gcwtone promted the joint1' Hr Aumim-Kenya.".I I I? I I @3dO&d h&@hg ~d Mind ~XphIti~~ROjeCt c0- the'II, Ti3itta-T~~rrPV ' i IIIL' I tbI' gbn m cover the ma with daded gurlogical fobwed by minernlo~'III' I 7 I &y of the vanadium godmite. MPgrretic pad &mettic atwapx.{R wvaing.. . the.:

L-showed r msgnetic anormly produd by a o~ocltitecomplex. As a reanlt of +

+ che ~wlogkdmapping the mawa. dividedhto three ~edona, T6.c project bzr thnefore made a &&cant wntribudon to our undcmt.an&g also improved ow know-

WOBI[\IMIHH}: 4thf [LVJI'KHI‘I ~uae,1979l'i I W.'-‘».7[ J. Wairegi“I'm-T: (Ag.)."'\,;. CHIEF('HH'J GEOLOGIST(Il'Llllﬂli

PubIiahed and pdnwl by: G&W der oeolopic und &gbrustudenteniq Clster- teich, Insdcut flL Geob@e dm UniversitKt Win, UnhwitItastrai3e 7, A-1WO Wien

. . MwatateiLHL‘\.\“u<_i'ii'i,:k‘ Quadranglei ‘

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Eingehend untuaucht wurden die Lagersttitten von griinen Vanadiumgrossulargtuy ten,. wekhe. . ala PdeLteine, . gmonnen,._|.l werden.. . Esz hnndelt sich hier urn einen Teilbereich des Mozambique-; Giirtels,- der seine let4 omgene Rwng an der Wende Proterozoikum/Phanerozoikum erfuhr. Metamorfi klaatische. I Sedimente\ ' und dolomitische'.. ' ' '. Kalke' mit.. eingeschalteten' ' basischen' und w ren (7) Vukaniten vertreten einenTeilder ,,~sagara~&cdimente". EingroSer Cha nockitk6roer..- . . da. von den Metasedimenten- :. eineehdt. ., . wird. k6nnte. in weiterem. Siaa. aterem. Gmndgebqe. entsprcchen,-. auf das die Sedimente. abgelagert wurden.. Klein. Linsen von Ultramafiten markieren vermutliche Auf~chiebun~en,an mlchen das ti fere Stockwerk in einer f&en tektonischen Phw aufgeschlejpt worden sein dllrftl Die Deckenwsteine -eeh6ren der Kurase Grunoe an.. welche hier in inehrere lith~ - . - ‘ stratigraphische- .. Formationen: . . unterteilt: . werden_ kann. Die sediment5xe Umgebung WI randlich.. marin,. mit. horizontalI ' I. und vertikal (zeitlich)' rasch wechselnden' Forks. Eine drciphasige orogene Verformung istgesichen: Vormigmatische isoklinale Fa ten IF, ) mit NNW-Richtunn werden durch ~aramkmatixheisoklinde und erne Faltc mit 'n&dlichem ~chaexub;auchen (F2) iibaprG. Weitwellige ~ie~efalten-sindd jlingste Verformung. Die Metamorphose‘.‘ . der Deckengesteine._, hat. die h6chste. Amphibolitfazies. erreich. Anatektische Mobhtion von saurem Material ist allgegenwirtig, so daO Bindergnc se, Migmatite und Pegmatite auftreten. Ein Metamorphosesprung ist zum charnocl &hen Gtundgebirge feststdlbar, welch- daGranulitfnzies zugehan. Mehrere akiive. ine' en in derA Region_ - bauen griinen ~anadiu&ossular. ab. Die LI -nerstatten lieeen in einem bestimmten lithostratiara~hischenNivcau der Metasedime te, und wed& ror_ allem. durch. den ursp~chen\I . besteinsbestand . , sowie. die, geoch._[ mische Bemnderheit dieser Guteine kontrolliert.

1.1.!I1rr-.-‘.1Jclm:': Inwoduction 1.1 General Thz Mwatate quarter degree shezt area k si~tedbetween latitudes 3'30' Sout and 3 45' South, and longitudes 38 15' and 38 30' East in the southern Taita-Tave District, Coast Province (~elocation key on geological map). Since the discovery of gemquality vanadium grouularite (green pet,Juvo te") in its western and southan part in 1971, the area has gained considerable econ mic interest. Although a printed geological map was available (J. WALSH 1955), tt was of limited use to gemstone prospectors and miners because ofits scale (1:125.00( Accordingly, it waa deaded to include mapping of the area at 1:50.000 among t tasks of theKenya-AustriaMineralExploration Project (1975-1978). The aim of tl regional work was to locate the gemstone deposits and occurrences on a geologk map of suffiiient ddto understand the regional controls governing their distribu on. In addition, detailed studies at the actual deposits were to allow a better under anding of their nature, thus assisting in a more rational approach to prospecting u mining. The Austrian Government furnished technical assistance by providing expert pe onnel, laboratorylfield equipment, and transport. The Kenyan Government ruppli through its Mines and Geological Department counterpart personnel, laboratory11 fice/camp and transportation facilities as well as operating expenses. AUSTROMIN RAL was the executing agency on the behalf of the Austrian Government. Mwatate Quadrangle

xm07:

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N! f1.\

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‘

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._ d , The project personnel involved was as follows: From the Government of Kenya (Minea and Geological Department): Mr. D. B. Dow, Chid Geologist, till end of 1977 Mr. W. J. W&+, Project CoManager, Chief Geologist from beginning of 1 From the Aurtrian Government (AUSTROMINERAL Ges. m. b. H.. Vienna) Dr. W. L. Wcrneck, Project MnnngerlMKmg Engineer

_ _ Dr. W. Pohl, Senior Geologist - An field geology (September to‘ Novembe

. intermittently)' map preparation and report writing (Febnury - March Dr. G. Niedermayr, PetrologistlMineralogist -Examination of rocks and mind, and preparation of an internal petrological report (January to March 1978). '

. The authors sewed as consultants of AUSTROMINERAL both in the field and r report writing.

‘. Also in mid-1977, an airbom magnetic and radiometric (spectrometer) sunry ( .

E veriq the entire Mwatate area was unied out by TERRA SURVEYS Ltd., unda ..

contract fmanced by the Canadian International Development Agency. (CIDA). A

. .

logical inte retation of the aeromagneric contour map (fq. 12) is presented in x . | W... ter 7.2 of Xis report. The results of the radiometric smyme briellyI described chapter 7.7.

A water research project funded by the Kenyan and Austrian pvlcrnmenuand a .. naged by AUSTROMINERAL commenced in 1977. It's aim is a new evaluation .

the Taita. - area's water potential udlising as a base the detailed geological maps p

‘ duccd by the Kenya-AustriaMierd ExplorationRoject.Hydrogeologicaldata on I h.

1 MwDtate quadrangle collected untilSeptember 1978, and their interpretation as tot m

<1 "I

I groundwater potential of the area presented in chapter 7.8 of thia report. This chiz

‘

L ter nr well Y &. 13 wnr mntributed by W. J. NAUTA, Senior‘ Hydrogeologist

.. AUSTROMINERAL Ges. m. b. H.. who is in chne- of the Kenva-Austria ground^ 1 tcr Raject.x

1.2 Acceua

‘

The area., liu immediately to the south of the &tly surfaced main road fmm V 1|

. to Taveta,. as well nr the railway line pasdng the same way. Both connect at Voi wi

the majorI traffic ways from Nairobi to Mombasa.

1 The Mwatate trading center lies at the northern edge of the sheet. on the west

H \

. bank of Mwatate River; it can be ruched fromNairobi at a distance of 346 kms, fr .

Mombuu‘ at 166 h.

\ The village Bura lies some 7 kms to the wen, on the eastern bank. of Bura River.

From those two settlements unmrfaced dirt roads and tracbr‘ suitable for four-

wheeldrive vehicles mainly allow access to all parts of the area. Especially . 1 r

‘ plantation'W south of Mwatate, but also hnle ranches situated further sout

‘ the West, have built a system of roads pmvidingreasonable access. by car t I of the sheet. Only during heavy rains may tr&c by vehicle be restricted by adverse road wndi- tions.

1.3 Climate and Vegetation Most of the area is part of the pattract of aemidplainland lying between the Coat Ranges and the hiidsof the Taita Hills. Hiph- mean temverature and low annual rainfall -be rise over the ~Linato a bush vegetation consisting of different species of Acacia, Conuniphoca and kuphorbia. MwatateM‘.\'.1I,1i1- Quadrangle1\}111._i._1_--.._

Limerich mils ovet marble bands frequently evrg tlmou impenetrable thickets of bush. undergrown by Sanphderia while much of the plains are expanses of open , -&d with scattered bwhes or stunted trees. The herhi I.II|.\ and.111‘. some\Iliill' ofH:- thdrII‘."..' doperM ‘E‘t'. mIll theTIIL‘ area.ilL'.l wee'“1'1IL covered. \1:"I"-1III earlier by open forests of hardwoodJ tms,[11:11. butI‘.1: extensive-,‘.\.tI.'I1.\1\1-'1I1.1r-1 chareopl burning hy leh only remnants of ,' 1 - - - -1 this'111'. vegetation‘.’t';=r‘[.:I]1'.'[| inIi] lessI135». readily1'1: 1- accessible11'1:‘~-.1IIIr' puu:\.11'1I.. The’E'I11'1.111151-5111I'ZII:.1.1:11I3111211111;111‘1'11 courses of Bum and Mwatate hrsa~e 1:?12mprked by fring.s of tall trees (mainly the ,,fever.21 -.':,'1' tree",:11'I1"..\1 Aca&.1.i.. Xanthopblo~)X.1"|-1111I1I- .1I. in=.11’I1-:'. their northern, upper reaches. Towards the . . south,-.-I'1I1 these11m... riven:'.--::._:1.1.,1;.1||\- graddy cease1;.1-.-11- to ~vrysudace17.11:-.'- water,dthough theL dwium con-. tains1.11111.1'11111111I1I.'.1tv: groundwater mu&1111:1I1 further.I111‘Izr1 There,'E'I11-r1» their1111;1'1l-1- beds-. are.111- cbterhd1|1.11.11 11-11-11 by \- lugeJ1”,- strechesx1r1-. '111- of::1 bkk3-21. I. ,,cotton1131- 111 soil"r: " supporting~.'111'-§\:’1:['11'1;.;.. a Ius6I11.1I1:1.1~.-1;'1-v::1 gnas covet.

1.4L-l PbysiogrnphyPI1I.-xi11gr;1phv TheII11-I111II1cst111-1111i-=1I11- highest point in the wen. is1- Ah.I'\I1.1 Hi1 Hi“ at.11 4369' (1332'| 113 m);1112.11 it 10i.\]111| part ofIIII\1:1:.1I1I.. Mgam , . Ridge,Ridgc. representingmph-1111:1111! the1I11- major111.1711. physiographic}‘-I1}5Ila}ll.s"3111 feature! .11111-11!1I_c.-.rc.1.I-1'.1'L: of the area. Lowerand.11.111'.1-1:1.'1x1.. more iao- 1 . .1... . Lted:.11-.‘~I hillsI11I\ occur- to11.1.1 the east.1 ads?) . south,-1~-1fI1. where9.1111: an111 almost.1I1111-xl featurelessIn: -=~pI.-.111:I>1 plain streches tc wards1111411111) the. south+ast.,.-‘[. It|I:1‘.1.,I-_1:~'I11:1:- reachas there a1 minimum-'1'1111111:.1‘1.11'1111-I1--1: altitude of 2250' (68611‘41. m).11. Most31111.1 ofr1! the[111;] hillsﬁ]|<,11<-Jill/411ml.1Ir111L1I1:,-11-._':1111.1I are aligned dong tho regional atrikcHid-.1; of11II rhe[I'L' rocks,I'I'111.‘. which‘.\'I111‘I1 Bin gene1'L'IH" dyjust113.1Luna-117111141. west of north. Several erosion surfaces have been dBerentifad1111.1. eattier1,.rI=: (WUSH‘31 -\1_i-]E 1960~5) 1_-1,,11;:. in1.7.111 the wider\‘u'ILIL‘I area:.H - EndCretaccoucI'.!1~'I(‘11‘[..1 (011‘ Shce51I11'1I1: at.11 4300'431T”? (13101 I H” m);111 '. hereI11-I-= occurringrI1-,'11r11ng.1111I}' ody at.11 Alia:\II.1.111.. and KideK1111: HiltonMpnaRidgeH1II\ 1'1:_.\-’1_-' - MnshotiU1. ..1-II: SurfaceSI at 3500'.1"11",1' (1070111'?"- m); 111' ; widely'.I.'11I1-If.’ erinent1':A.1I\:cr1| on1111 hiusI11II- in1:: the1I11 north-westr1 11'I1 111,2! and.1111I , = - - . . - - 1 -1 north11II1I1:IIII:11,"1I11'L'[1II:11:1~. of the sheet, fomts summits\zlllilnlh ofI'II Sembii\1‘1I1IJ . Waoni,3.1111111. MkmgareniMxL‘JlL‘c1'C11141115MIKL‘I: and Mikdi - MwangareMw.111g.1rc Surface\urIJLc at.1: 3100'HUN. (940."-'H| m);:11 .::1.11L1’1I\I11-51-o-.11.111111:r111.1;1r1 marked shelves on met hierhitL I11]Ia.11111a11111 and sum- mitsH.I1-.-'I1 of Pusa,I"..1\‘I[1"11'.L'.1,I*{II::' Mtongp, Kore and1‘11I\'11111I1 ad& - Subhaioctne5'1? ‘111-=.,1‘1'1-:- SurfaceSurf-.1. : at.11 2600','1'-.r'111' (790'.-"1[] m);1': : dippingINN-111 at~-' 9'"‘ par-de[mgr 1:1iI1- to1.: the muth-.south-.1-u1l1x1--11I1 I east.1'.1\[. hlortN'IH'.’ of111 [I11' hirrI1i1'I1r-1 -111111u- cq1.111}' lit&IIHIL‘ SV~I-=OV~S,~.111I-111w-1, ~11LI1.1[LIIt'I1]II'-.1111Ili11‘11.LIII;1c‘ the hius urd tkcir dews pvide]3[-3|\'I.L1L‘ reasonableTIJ‘I'r-IJE'IAIJIC mck|\'111 I’. outcmpgIII:T_L1 :;1~. LowerslopesareL|"\\1'L'I'\I\|}‘C1 .lI'L'l-kk1IE-IUIJ1;II¥Lf\\'CfL'l:JIl‘X'[1lIi}'. hccssionally cowredby trlus;very\'Lr‘..' thick[I1]. 1: dusr.I1:\.1:1.. and so&..1.i[. are11:; typical111,111.11. for{:11 the(I11- pediment11.1111»- vsna.. 1-.1-. surrounding.1 11 1'1'111'1d1111; the211-; hills,I11II~:. m..1. wellL'II as.1sI-1: for theII:- ph.:1I.1i:1~. With\\-"i[I'1 the[1'11- exception1‘\11~',"i--r‘. of1-1 BYTB[$111.1.1111I3‘J‘.v.11.11rand Mwataae Rivers,I'litrtk theZI1L'1111Iy only watercourses\I.'.1[:_'r:rI'11-:s.11=: are mere||'.I"-'

gulliesL."-.II11" wW.~.I111I11I1v.1-dim 1 theIIL1'1H'1I'.‘&"'L'1 steeperI hill-sidesI11II «1:11-1.1r11'1‘1I11,' and the pediment111Ii111c11: areas,.111'15 butI'lll disappear1:. whe- m[L they.1‘11"1'-III‘1-"1|:‘.11[‘|,.> corm into the plains.3 ‘ .. fl These1'1L"-| gullLsIL-1:II:-.-‘ do11-1 not1.: -. carry1 11:1' waterI.I.'.1.L: expen dwing very he- .l\"1' [' J‘II:‘- Waterkoler\K-'.11.-1-11.-.]1-. oecur1.11:: in111 the1111- plpinap].11:1« at111H.111".I.-.11ct1*r.11111.1.110:1-11I1'1,1\.111I1 placeawhere rain water conects in little-|1- podp11111I\ be.1111- to:11 more1111111- impervious1111113111111. soil.1111 ~r-11 KO&1'11'115 underneath.1:1.11-1111-.1‘.I1.51.1..I1 Such water11.31111 is1&111-1 not an.1.- indication:111I11.1111‘111 of a.1 1 1 Wbw\i’1lItlI". water 21.171” trble;2.1!: 11-: therefore':1- '1 !-11: the‘.'1r. water-hole8'-.-..1171_'.' I211I1'5 fall1'.!iI dryIIH' byI"‘1'1"-.'.11‘II}'.1|":I evaporationI. during‘.i the dry season.~--c.1~- I 2.' PredouaPIN 1011‘. Geological{:1-11111g11 .1I WorkWnIL TheI'I‘.L' Mwatate\1-\-.1.1r1:c quadrangle11;.11I1.1IIL'_§C- was-.'.1 inddedI51 I|.11I1‘:I in111 rhe1'1c 1:125.000I: .1.:J'111 sule gcologid map by ,.,I,. I _I.,.,I,. \’\:\1..\.|i 1'11111. The io& of the'.1 ,,Basement|‘-. v. ‘ 1 System"wenL‘ .' 'J.‘ then:I1131: ddmd11111-5. :1-I to' :::-1- be of1: Archacan:\:1.'.' '1 age -useI1 1| 1 of ’ theirI? &h-gr.del 1" metmo'phism.. _1 I WALSH‘._\'.\[ SH mapped::.1'.‘I.'-- .I these1'51: . rocks: -. as.1-.' a suit~of I W. Pohl& G. Niedemuyr paragneisaes, including gi-anitoid gneiases, crystalline limestones, graphite gneisses schists, as well as biotite gneiues. The general structural pattern of the area was recognized as that of a se folds overturned towards the west and pl- northwards. A metaxnorphirm of amphibolite facies grade followed by intense alkali tism and granitization were. deduced from the study of thin sections of the r Since then little geologicnl work has been done in the quadrangle. In 1971 deposits of green vanadium grossular garnet of gemstone quality und in the west and south of the area (BRIDGES 1974). This prompted an prospectors and minen, and the setting up of the present project to assist those le by proriding geological information to guide their work. Mineralogical studies of the newly found garnets were published by SWITA (1974) and in 1975 by GOBELIN & WEIBEL; the authors ducribe physical pm ties, list chunial dysea. and communicate microscopic observations of the garnet variety.

The region- adjoining. the Mwatate quadrangle is covered by the following pub tions: To the east and north-east. SANDERS (1963) described a nritc of ban& tites, microclincrich gnnitoid gneiues, biotite gneisses intercalated with rous, calcarwus and graphitic gneisses, crystalline limeotonu and amphib ping steeply to the west. Three partly infond lithostratigraphic units are ducribed: - a westernmost aeries of garnetifemus and graphite gneiss intmtratitisd blendic and hornblende garnet gneiss west of the Turn - Athi rim co

to the south mysive ho&blend&met and hornblende-biotite gneiucs ‘ the hills around Voi and on Sagala range; tight isoclinal and some more are typical structures.

- to the east continuing to Ithangethi on G&a river banded and contorted‘ h blende migmatites are common, axialplane folding and boudinnge are - east of Ithangethi the, migdtesgive way to a non-migmatiwd asse ally named the Sobo Formation. It conaiats of garnetifemus acbists an

thin quartzites, abundant crystalline limestones, Wehornhlendic purses1‘ dark garnet amphibolites. The SobooFonnation forms a wide open syncline foliation dips generally less tian 30 ;the western boundary ia considered as

faulted on thrusts dipping\ 35 weat.

Potash feldspars from a pegrmtitc outcropping one milc south of Tuvo gave. a

~r-ageof 560 f 50 m. y.‘ (HOLMES & CAHEN 1955:12).

To the east and southurt SAGGERSON (1962) dehed and named fodyh litho~tratigra~hicalunits: the Kaaigau Series, and the unterlying Kurw Suies. The Kasigau Series consists of hornblende-biotite gneiuu, kyanite-biotite gnc quartz-feldspar gneisses, calcareous and granitoid gneiases of an approximate thii ness of 11.000' (3.500 m);the top, however, was nowhere seen. Typical structures are open folds with a northerly pitch; migmatization is only 1 dyintenae. Of the Kuraae Series only the uppamost 8000' (2400 m) are obIwlble. roc und are kyanite, graphite and quartz-rich gnciases and crystalline orphiam u of amphibolite f&s grade (rillLnnnite - almandine s Mwatate Quadrangle tasomatism is widespread. Folds are overturned to the west, with a north-northwester- ly plunge. Although the difference in tectonic style suggests a discordance between the two Series, this was expkined by disharmonic folding. However, the difference in nature and direction of both sets of folds is interpreted as being due to two phases of deformation: A fxst one producing overturned and recumbent tight folds of NNW direction mainly in the Kurase Series, and a second one causing open folds plunging northwards and affecting both Series. K/Ar-age determinations on feldspar porphyrobksts from Maungu and Nyangala (Kasigau Series) gave 490 f 25 and 425 5 25 m. y. respectively. At Mangui, south of the Mwatate quadrangle, a deposit of gem-grade rubies was discovered in 1973, A yet unpublished report on the nature of this and associated deposits was prepared in the course of this project (POHL et al.: Kenya-Austria Mineral Exploration Project, Rpt. 9, 1977). The rubies are products of desilication of alnmi- na-rich country rocks or pegmat~ticfluids caused by ultram&c rocks. These rocks were recognized to occur in lenses forming a belt along strike within the Kurase Se- ries. They were 'originally dunites and pyroxenites, which were affected by at least the kter phase of deformation and metamorphism. West of the Mwatate quadrangle the crystalline rocks are poorly exposed (BEAR 1955) except around Taveta, at Murka-Loosoito, and in the Longalonga hills. Of interest are garnet-biotite gneisses, quartz-feldspar gneisses, basic to intermediate char- nockitic rocks and uldcbodies around Taveta, kyanite quartzites and schists from Murka and Loosoito, and graphite-kyanite-muscovite assemblages with fuchsite and apatite at Longalonga. Regional strikes are west of north, dips moderate to steep to the east. The region north of Mwatate was described in a very general way by PARKINSON (1947). A more detailed account of the geology of the Taita Hills but centering on their asbestos occurrences was given by FARQHAR (1960). SHIBATA (1975) determined RbISr ages of 827 * 55 m. y. on whole rocks from the Taita Hills (iochron di- sturbed), while KIAr ages are 498 f 15 (biotite only) and 519 f 16 (hornblende) respectively. Geological maps at 1:50.000 scale of the Taita Hills, Maktau, Kangetchwa and Ma- nyani quadrangles (Rpts. 1-4) and of the Mtito Andei area (Rpt. 5) with the respec- tive reports were produced by the Kenya - Austria Mineral Project in 1976. In the Taita Hills a lower hornblende-biotitegneiss unit with minor mubles, kyanite and graphite gneisses was differentiated from a higher quartz-feldspar gneiss unit with numerous concordant bands of plagioclase~pidoteamphibolites. The contact between the two units is marked by a series of ultramafic bodies, which have been introduced before at least a later metamorphic event. They have frequently serpentinite cores surrounded by amphibole asbestos (talc, -carbonate) rims. They were interpreted as having been intruded along a regional thrust-plane with the same strike and dip as the foliation of the metamorphic rocks. From petrological studies two metamorphic events were assumed, an earlier regional one of amphibolite facies grade, and a kter more themd metamorpFm of the same facies. Structures are very simple; foliation planes dip generally 20 to the north in the central part of the hi, but dip more steeply to the northeast and east in the west as well as the extreme east of the quadrangle. W. Pohl& G. Niedermayr

A coloured: geological‘1‘ :1 map‘ : 1:50.000" and an updated report1‘ on the TaitA quadrangle is beingw. published1 1 : contemporaneously by the same publishersv (A. ! KEL, G. NIEDERMAYR‘(L [1 l."'|.‘. ‘h & W.'ul POHL,NH 1979)..

3.\ Summary‘kmmm ofm Geologyt :w‘ rv

The Mwatatea" arearm liesH entirely11 within1‘ the Mozambiquel \ Orogenic‘ ' '1'“ Belt,I whichd : tends fromr-‘ Madagascar.w’ . ‘ andm Mozambique".‘w m ‘ through Eastern1 1 Africa: into1‘, the Sudan. . possibly to Egypt.L {W andm: Arabia.“ The‘ Mozambique‘J ‘ ‘ Belt‘ was fust1 described1"" and. Y nagi by HOLMESW \I (1951);-‘ thisI l belt consists of high-grade_' . — crystalline{1.1V rocks,V has1l an ipp4 mate north-south' orientationw“ w I“ over its7 whole length,1‘ and4v: is chamcterisedv 3 by, ages in$ range ofI, 400-700M b‘ m.v y.y (CAHEN| \i l 1961).‘1 It‘ certainly containsv v rocks‘l‘ of1 many 4 rent ages, and:1 is essentiallyL _\ a‘ zone ofH old1‘ basement1 with a sedimentary‘ cover wbi together sufferedH' i severalv'v {7 phases;‘ of deformation‘ m and metamorphismV‘ . “I 3- (HEPwOR~ 1971). The1 last1m ’ overpdntingW" T 1“ '_ occurred during_ the Pan-African‘ (or? DamaranVi‘h v: - Katlr_ gan) Orogeny,‘2 _ 1 whichJ. lh took place; around‘ thew turn of‘ the Proterozoic to the Phana1' zoic (550"-r‘ f 100l w m. y. accordii2‘ to CLIFFORDr ‘ H H >\ 1970).‘ The crystallinex !' rocks of the MwatateV H area arew metamorphosedv‘ ‘ pelitic,; 1 arenacec:v . and calcareous‘ sedimentsH ' withV“ intercalated'H 41‘ thin bands‘ of basic sills~ I or lava 5ows, me smallMy lenses of ultramaficM m rocksi emplaced1, along‘ ‘ certainr“ lithohorizons,"‘wiwl and1' a Lu cbarnockite body. WithAm‘ the'r exception‘ 11w“'w of the latter" they are all“H: part of the1 Kurase‘ I ties (SAGGERSONK" ' cl‘ WM 1962).W. which in accordance. ‘ with modern‘ ‘ nomenclature' ' (HE

BERG 1976)i I shouldl better be‘ named‘ ‘x‘ ,,Kurase‘].‘l ‘ Group".‘ The meta-sediments1' ".‘L :I‘ andL thek cndomdM ‘ meta-volcanicv ‘ strata are partI" of‘f';!- the Usap.._ u Metasediments211' (HEPWORTH[WU *E H‘ 1971).1 generallyl“ , \ accepted1‘ as constituting1 -‘_ a sediment8~ In suite Lid| downV.'. onX.‘ older[:3' cratonicw“ w basement.1 'HAM Theilv charnockite3: 1 r H of the present“1 area5-, (p]\ sihly comparablewuu‘ll-‘u to the“v EasternN GranulitesIHEPWORTH‘M:‘J.‘H" M WmH-JHE 1971)w mayx representv parta this basement.x m The following:n 1h lithosuatigraphiciHhHHHJHQHI‘hE‘. successionm L w hasm been established< in the'1 quadran‘v .5. (see also table.z' 1):i

Mugeno FormationF» ' estimatedH" thickness in metres. ,,- 900 + Characterized by«. numerousH' n handsm‘ of’ (topin not defmed) crystalline limestone,'l ‘P‘M‘ intercalated\ I L1H! with‘ " biotite (garnet,'. -sillimanite,.1'1' mm?" graphite,.‘11“\V.‘ -kyanite) gneissu andw quartzfeldsparT‘.‘ 't i (garnet) gneiss".l“

Mwatate“U: ’H FormationE H ‘ ‘

Essendys‘n thick and uniform‘ biotite - '1 (garnet) gneisses,-_' banded.H‘ gneisses,'x' py-,w' ly migmatized,. alkali-feldsparI} L M {1‘ growthM wl- despread,W. with? importantw ‘ H layen of"1. plagioclase amphibolites,L'M" and1* some minor bands‘ ;: of quartz-feldspar= ‘z (garnet)‘_' r gneiss,1 marble,‘ and kyanite, (-sillimanite,'1 Mn-).. quartzite .

‘ .u

1‘.

I..

‘

.... .

.‘

. nowhere exposed; locally discordant boundaries can therefore only be wumed from the dimihution of the endosing ma- -rble - bands. ------Mtongore Formation

This formation b only putidly exposed, (base not defined) and its buc remains undefined, as it is outside the Mwatate qud-qle; biotite (gy- net) gneiss bands seem to be the characteristic ro&

Structures observed in the Mwatate quadrangle point to a history of thee p of deformation. At outcrop scale, pre-migmatic isoclinal axial plane folds (PI followed by moderately tigbt to isodinal para-migmatitic folds and boudinage A third, probably post-migmatic phase of deformation (F3) created wide ope res of wave-lengths of several 100 metres to a few kilometres and probably u so postzrysfJLine jointing, wide-spread utldnsir, and local faults. PI fold axes plunge at moderate angles to the northwest and are asymmet overturned to the west, while Fa and P3 folds ace north-muthorientcd and dip n wards. Vuivlce of the stated direction and anglcs of axial plunge is imporrant. may pdy be understood as rotation and resultant scattering of urlier linear 6 nves by later folding as described by SANDER (1948:177-178), and alao as de dance of second and thud folds for their uirl orientation on the attitude of s on ich thq formed (WEISS 1959:95-102). The most conrpicuoua foliation planes are nearly always parallel to the o boundaries between different rock types (So=Sl), although traces of a tr have occasionally been seen, both aa a para-cryrtslline transvuse direction of the 04 entation of biotite flakes (Sa associated with F2) as well as post-crystllline fracq cleavagt (S3 associated with F3). Foliation dips are generally at medium or moduate anglcs to the eastnortheaa F1 and P2 folds caused a left-hand displacement of continuous lithohorizons aloq strike, while F3 folds led to medium and large scale warping of prmioua structum The existence of a large anticlinod structure in the aru as suggested by WALSl (1960) .could not be confirmed by the present mapping. Although axial plane foldin at minor and medium scale has been observed, and some repetition of lithostratigraphi sections certainly exists, the repetition of such sections at a regional scale seems ur probable in view of the now detailed knowledge of the lithostratipphy of the am In a regional outlook, the deformation pattern recognized in the present area ma compare to the ones described from NE-Tanzania (HEPWORTH 1971) and wester Kenya (SANDERS 1965) as follows: I Kasigau Group (identicalll with‘.' i": ,,Kasigau. [‘. l‘. Series"1SAGGERSON 1962) 1 I estimated thicknesdmetres

Mugeno\il-Jlll‘]'l|!|'|.:|."|--|I Formation 900'.n + " (marble,rswll-I: biotitegarnet-kyanite-jillimurite-graphitei I. ~~'H'=:'.||I|In' .“dpi’alfu and.1I1:"' quartz-feldspargarnet (probably around gneisses)-"|-'. 4000)‘IIIJ'II

Mwatate Formation '.IIHII (hiotitegamet gneisses,H x‘ banded'1 mute-1 gneisses,ﬁ_l1»*!\:.1->, migmatite,mi. ]]|.:' itr'. phgiodase amphibolites, minor marbles-]-, 7. and7-:1.i kyanite-silhanitequartzite):. 5 ..:mr: ammuni-

Kurase Group MgamaMindi“ .| .‘~‘ll."||£; Formation}-. I.’:Lt!'--II 5000 ‘7’ ?tic,-J'I,".': (? biotitegraphite'l'-|-:r=.‘L1‘1.tp||'-h--. gneisses, thick hands of marble = higher part)envelops the mth ,,Kurase .------Series") Mtonga-Kore| |\--r;1':1rJnu-Llaltr| Charnockite Complex..-; . . . , ‘ SAGGERSON (intermediate':=|il HI c-,:;..I:; toI J- basic charnockite,".- :1- , »:.... plagioclase12.1.91.J.|«-;.»iir! gneiss)\ 1962 (lowermost part of formation = graphite-sillimanite+iH3II:.I:-!Ir gneiss,.Im iw.. with-- bands of granitoid and quartz-feldspargarnet gneiss, marble, amphibolite;.I my] high geochemical dues in Ni, Co, Cr, V, Cu and Zn = I Lualenyi Member (host to green groasularite...'i[:‘. deposits of the area) Mtongore Formation 2000 + (biotitegarnet gneiss, banded gneiss, marbles, quartz-feldspargarnet gneiss)

, base‘.l‘ yetL'1’u undefmed:.[|-.|\|].'.L'.I

Table 1 -Summary of the lithostratigraphy of the Mwatate quadrangle. SE; 700-900 m.

Metamorphism is of high grade; mineral assemblages indicative of both mphi te facies and granulite facies have been detcnninul. Rocks of suitable compos I ahow anatectic mobilization.. of feUc material and growth of potash-feldspar to

typical banded gneisses. Mignuhtion,, however, involving bloningout of en tures at outcrop scale, is quite loulired. Venites, agmatita, and nebulites observed. More than one phase of metamorphism. are thought to have occurred in the area.

phaae may have taken place contempocaneody with PI deformation, possibly a . iated with inadon or tectonic emplacement of the ultrnmafic rocks. At the pr . stage of knowledge,. nothing can be added on the natum of a possible early met ph.

The major metamorphic phw in the area is associated with F2 defonnati c find mind usemblagcs indicating high presaurcs and high temperature, inc the kyanitealmandine-muscovite nrbfncies and the sillimanite-almandine-ortho subfades of the amphibolite facies. Some of the fclric gneiss bands within the sedimentary suite, and the mcks of the Mtonga-Kore Chamockite Complex rho nulite facies feanurr; the felsic granulites by the typical discoidally danened q grab, while the latter are chunocbpropa, containii hyperathene besides side, hornblende, both feldspars, and some qua~~z. The pr-conditions may have reached 7 ldlobv and 700°C; this uuaed mobition of f&ic material, and a widespread potassium metasomatism, wrentlv rest the KlAr radiometric ~s. he'^, phase may have been acczmpanicd by the more thermal phase con from the obacrvation of dlimanite replacing kyanite. Penetrative pcgmnites, Itiog mainly of qwz-feldspumurcoate-fourmaline ue thought to have o during this latest phw. The formation of the Fecn vanadium gro&te hataken place during the metamorphic event wherever suitable material waa available; a weak retrograde se may have cawd the kelyphitic rim around the garnets consisting of epidote, s olite, dinopproxene, and spinel Soil. ye generally residrul, of reddish colour, and mdy. ~i~htgey, ulcareous soil. occur above crystalline limestone bands; ulcrete layas may such soh, but frequently form a hard crust with little cover. BUcotton found covering some low lying areas, but typically form a blanket above the '1t should be noted, how-, that SANDERS considered Bz to be penesontem rvleous cross folds to BI. 1 Mwatate Quadrangle

0 e-: Erosion|..-a~..-.‘:. anda:-..: peneplainisationpt_-Ju-;l'.ullir:i...'.ian Segmentation‘M-LII of the1 crp$t&e_ rocksx a-. n Deposition[Liflwuuiiitui'l of-'. Kuoo-sedimentsK..J|.!ll'l 5:3...- ' ?'r longl::15;_'1‘_‘_._'|-II'..II regional zones.r‘t\|":l‘- of-:,' catachis._ .F..:l.i\1\ (lineaments)'_|'I|"|:‘.|||Ei'.‘-:'l"- VpMtE and.mui erosionmam-m

.7 F3deformationI"; -lr.-'.'r.\rn::niur1 (open,-- undulatingIli‘illidTnC foldsIf“: withWith northerlyHurtizv: trend; ,,pcnetratiw"..‘lwr'n-tr'.11;\-'c“ peg-1‘ -4 nutitea? moremenu thd[E]<_'l':'i'.-l] metamorphicEI':CF.1[}]:1E'§¥]1é-_ event,31‘”! . cataclasis)L .zt..1-. .. 1:. wit]: ::-\:L!1:':j}' [1"- 1'.2'.‘.|[‘]1E1‘*'|E|[{'_-'\J_!'.i'.'|'L}![L‘[-‘.Ll- U. Ft&formation (axial plane folds with northerly trend, unphibolitJgnnulite fac- P:1". ie~,we. metamorphism,HIPILIIL- ‘~!‘.]. anatexis,rll1.1LU.‘.iw. migmatisation)i'i!!._::'l1.'d-'.I\.I.[l£}ll 5} .17]F, deformation-\}I|_'|{ HIM-titan (axial.._ii.‘-.'.:{I planephngt folds. .iu‘.|.'itlls\5N\\e" with W-trend,[I'L'Eh!.||'.L‘1..l}|}"}1']3}li'~ili.-'. metamorphism?, regionalII.‘_LEintl.I.i thru-:llrn- u.. stingSIiI'iL", with\\ iil'l obductionlinvusionI_:i.‘ {an [inn iil1'!|1'\jl1!! ofL31-IE][F.iEELi}-‘lt. ultramafic roclra?)5-.n.ks_" a Sedimentation.EHIL‘TH iI-1'.- of.-.[' KuraseKI. in Group(Hump on21m a.1l1.I-..cr~.1c:. basement, whichhiljh may|!'..l\' behe represented by the FI Mton~a-Kore:I'.;'.:-l\u'rrL' Chamockite‘. |‘..1rr1t>.':. lL“..\.'|.'J{'!1.f_... Comokx. TableWilt-'4' 23 -Summary511111“; "'\'!L[U\11EJ: of geological£.1§£_".'CH.Y‘$II'| evenw in the11W.‘\'l\\'.|i.l.[v,il'a':1 tdwatate area

of the streams=.-‘.rc.{'.:1:~. and.Illui rivers.Til-'(‘i'xﬁ ThisTM.» isis thought tor-'- consktum ofmy}: gravel=\-"'].l|1|..~:41‘|-1. and sand, althoughiltémzlgh iti1 was‘.‘.'.::- rarely sen-.1c?xl...\.c:id exposed dueas. to:. the'_::-\' smallmuli amount.4..-...I.I.:1I_ of:-i' actually:1Lr.u.4l':1: &wing'1 'illgwuh'! water in:r.‘..|1L"1':L-;-r.». the rfvars.

4. Lithostratigraphy{..Hlu'nthHigrdpl'ly and.l Petrologyl’utrt'mli‘iiﬁ'

~‘I.l [.ithtntruligmphy TheT‘m.‘ MwatateMu'm‘q quadrangleL1 unhiny‘le isi> completely-.'-.JII=.p:crL‘1}".\":-'.]1i!: within the111:.- domain.{nllmin ofIii-11:1; the suitesLIiLL';1)"r:iL'-'..[;}c of meta-pe- lit-lit-w and.|::.:. meta-calcueous'11ct.u-r.li.u:1ra?-H'.» rocks."-Jt‘k~; namedname-1 KuraseKllmse SeriesSHEER» byL}- SAGGERSONSAUUEHSUN (1962).':_1*.)(\2_,.'|.']1';\: Thk lithostratignphicIHl1lJSIi-l1ifl1'.:§1]li\ unit1.17m couldruLzLI be3n; mapped1|l.1131‘{_’;1l rimilvlysimildily in'15;- theLE:-TaitdI'Iiux.[\1E1_)ElU\1AYR TaitaHills (NIEDERMAYR et...-‘. al,.ll... 1976)'I'..|".-‘t: as.12 pmdictedprL-Jiutcd by'3"; SAGGERSONbfiujlllziiSUN (ibid.),“13-35... and.1n-:i fwherZIUILEHJT to[(1 theLbs northwestIl-Jl‘i-‘QS‘; (HORKEL:HLJR‘RICL &5' ELLIOTl',ELLIIJ'I'T. 1976).l‘l't. Accordingly,Agnjcunlinflv. themu unituni: isi-i-;I"'-]1}[T'1Hl"x‘| confumed as.1:1 beingl\L'i]1-‘.;-‘311‘E=. of regionalIzml importance.i!::pc}1':'.mm:.|! It should,n]1uuk§,hr:v.' however,even. be[up renamedrcn .um-n ,,Kurase.. .lif'hL' Group"I'm p" - according.iil.l\:'l]i7'|;_'ll:|l1t]-..1L'[‘-]|'|-'] to modern lithostmtigraphic-::1r.|:ig1.li.\lli=..11- nomenclature[lt'ld'lll‘ : (HEDBERG'I'if.lll’al:1i(.'; 1976).1!. . TheThL' presentE mappingumpi‘i‘. in the'I1':‘~':\V.l[¢:[:_' Mwatate quadrangle- irallglc wasw.1:- of sullicient-.'1i_1_i._'!a;11{ detail.-.rt.-.i1!cl.11]-.":w.1 to allow a further subdivision~.1|.'!nJi\-'i.~.iz-n ofVJ? the[INC KuraseHuman; Group[hump inin the:1“ area..:r'z?;.. Newv lithastratigraphiclit|::_>\1:.|!iu1'a'}1||iv unitsI of theL.|‘_‘ rankHEEL; offormations:.t In! ||:.1'_jc';.n~. could._.mM be1'.“ dehed,as'_r.:li. '.\.' wellVin?” asilk one{\IIL' ec~nomicd~important{'a_r.[1n1|i1g.,- ..iE‘tIi'1;1I‘-.-’ mem-::.r]1: . ber of one of the--1n:';JI.n=.- formations:. (see tableu|.. 1).

4.1.11.1.1 The MugenoMugt‘m.‘ Formation[:1'FTIIIJTitll': is'1» ther':‘ highest_lli:$1 lithostra~igraphical|i1|1l;oit'.st:' '._|P‘|'.i|_.!.: unitunal ini:' theLin; area;\l1\‘\|:-f'-[ only its.[\ lowermostliar-won n-s-t partpui'r. lieslim: within2x thethe Mwatate‘.'-\v..r.|rc quadrangle,5;: .nh';111_._r§:-. exposedu_-.\pu).<.L-.i. onMugenoin; ." Ridge in the northcasternnorth cusrr-rn corner{mm-.- of1.1 the1}iL‘\]1E'i‘[. sheet. Here,HI-rc. numerousnull-.2 marbleIMI.‘ bandsIii:}}-.:.'4‘\'.IEI]1:ll‘hL‘ with thicknesses up to several'['..-| tensH.‘ 1'5 ofI11" metres ace in-in tercalatedic-1-..-.]--'-;a'l withaxilll biotitei‘iu'ntih: (-garnetL=.n!':-._'[ -kyanite v.‘_.'-. ' - sillimanite-.~.i||i:‘..lr-.ilv gcaphite)-.,*_r'.np§aitn' gneisses,1‘ and schists,iv.» and3.1.1. the:‘II-n occaJional. -.-i. -]|n.:1.1.=‘. band of typically'ypi. .Iily white‘.-.']..i'<_ orI-I' buff1W2?!- quertz-feldspar-'l'.;.l."?.’ SH». ‘! (met)gneiss. -..\. TheH'r base'.|-.t' of.-‘.- theIi“. Mupicno\1l1;t'||.- FormationE --"".1.;r.i.I-I| is taken..L z :. as the‘11L— lowermost].-.\- . 1‘. reasonably continu- owt1.i.!':'|.H|‘l|.' marble bandL‘Mnl on"‘. the western‘ . I: r footH ' of.' MugcnoNIH“. 11 Ridge. The top of-'. theTII:_' formationfuu'..":!-.{t5.:'-. is . I . . _ : oauide”HRH-l; (to'_!- the‘!ll' east)l.|" of- : the'.||I.' Mwatate-‘I'L\'.x1.|‘.x' sheet;'Iuw' it' is. considered to be the major|i|.'...[ lirhostra-l]|l|l.'.‘.':l tigraphic2:;[1-1}.‘illl_ hiatus between*‘wm‘li Kurase|-\_;-_._\-_- and. Kasigauh..:~i-'-.:.( Groups, now well known from recent mapping in the Taita':ai1i|l~.:.\'l!'i)! Hills (NIEDERMAYRi-z'-.’..-\\-'|:_.-._-.-.__: et at., 1976). About 900 m of the lowermost part of-‘. the!|1r_- Mugcno:'\'1i'.L_'r.|1.-"\ Formation!'--In:'. lie within the Mwa- tate quadrangle; the total thickness".:'.\\ may be up.1‘I' to- 4000EHFIl' m.: .. Mwatatev‘J‘J. .1141» Quadrangle("‘2” .mmﬂ‘,

. - ‘ ‘ . ‘ .1 k37 ErosionE: H andmm peneplainisation:gmiahmzmnrrm Segmentation.‘wgn vnmuun ofH? theV". cqstalliner}«[.q];1m-y. rocks a- q DepositionMap 4:1.‘31 of“17};t Karoo-sediments‘ ‘pyflfl, 7:4 longwnyu-Lmn regionalfi mmmuizones of catachis‘,‘L:1‘}“.\i‘~:lEIlL‘J'll‘Jrll" (Lineaments) 2 Upliftlr'phi" and.m i erosion”my.”

if Fsdeformationi-ur: (open,‘npczn undulatingI::Hrz],uing foldsinHk withuniti‘ northerly:‘.uH]1v,'rlj.'[H‘z‘ul'..pL‘!xr,-rm!i\'L”' trend; ,,penetrative" peg-17"" 4«i matite~?!:L.i[iffi”\“Hi“C:1H"[[HJ]HIt‘LHH‘H'I‘lliLL‘\CIL[.\4Hdtlu-i‘wmore thdmetamorphic event, catacksis) 1. F2deformation{>8617n15n4téwn (axialaxial planeplum foldaf‘>]‘1'»‘v\'l’.}'\ with northerlynullht‘lj')‘Emmi..L!!.::}1Hw]ilv trend, amphibolitelpulitepmnnlitc fac-hr ‘d:P ie~,its, metamorphism,XML-Lunarplnnm, anatexis,:lYLHA‘\.;:‘v, migmatisation)HIindflNJMu-T] 2:f‘ Fkdeformation17' «Lglwrnu rm (admum] ~kneplum foldstk withNNW-frend,withN\\\‘ 'IL‘IL’“T11(‘[.1111‘12E72'11-f31 metamorphism?,~1'K‘}:i"‘l].ll‘h!"3* regional thru- LS stingarm; with obduction/intrusionm {ULti‘flll‘iHTIHZNiUU ofM7 ultramaficHlHJmafL rocks?)x-ufix‘ uLL . ; . , ‘. Err' Sedimentation\r-JeHTAKi-w‘. ofw' KuraseH ,.l»r‘ Group(aTHLJP on(1H a‘L"‘AHCHLL’IN.‘.‘.}11(HYilt.‘.'1"t.‘ basement, which may be representedYL‘1‘TL ‘7: ILTL'C by1““! the? ll' s. Mtonga-Kore1\-11‘=H:._".-. Hum Chvnockite(,lhdrnmkizv: Complex.' :rmplwz. Table'I't: 2J - SummarySmrmflan ofw! geological.tn-nlxmimlwwntxint1uw\1uum:.c events in the Mwatate area

ofw'v the{hr streamsar'mms andJIM rivers.FIVCTL, ThiiTliix isﬁfth-Light thought to[w consist. wlvxiat ofgravelm ,114 andJHEIMHI‘E.41§}'I\1L'.L'.HH\.‘.‘.I\ sand, although it was

rarely seen& exposedOxpxmmt due‘11:: toEx.‘ thetip; smallvzrmH amountumwzm, of‘ i actuallymmAHu flowingHuwihg watervmm inm thethu rivers.[hf-Cf}.

4.4‘ Litho~tratigrnph~I ltllrmlmllgmphy and PetrologyPctz'olagy

4.1 LithoruatigraphyI ilhuzfrdligrdphy The Mwatate'\-‘!n.zr.1rcqmuimnglc quadrangle is35 completeIygmm‘plctcly withinwith}! theThe Jntmindomain of the[lac suitemite of0f meta-pe-HIL’LrPC' litesFix» and.md meta-calu~eousmum-L13]..nmsuk mcka rm‘h namedname} KuraseKumxc SeriesSuit-5" by. SAGGERSONH.‘\(_;(;IERI$¢)N (1962).It‘ll/3'3. This lithostratigraphiclirhmu.mzigmphil, unitmm couldme beN: mappedmappe“. similarlyaimihtly iniu thetun; Taita'l'aim HillsHill.» (MEDERMAYRuNIEIWRMAYR et1:: al.,.Il,. 1976)l“_‘(': as predictedpnflldc-i by[.5 SAGGERSONSA(,}(]I.1~’5K )N (ibid.),HWMU. anddIl‘i further{llxthcx toEn the[he northwestHurtllwcst (HORKELHUN Kl:l.u\ & ELLIO'JT,["1 l [01”]. 1976).FUTUH Accordiiy,:Mufi'dingéj,‘ the unitunin isix confumedUnflimm‘i asw being ofMfr regional3 "‘zml importance.impmrmn: L‘. ItIt should,~hnt1la1. how-ELIHAA ever,mm. heby renamed[mmmmi ,,Kurase“Kmaw Group"(Map? according.uu’JI‘IIH‘|_.1 to modernmmivm lithostmtigraphic“Illufll atiguphi: nomenclatureI‘ll-HM‘ILL'EAILLZL‘ (HEDBERG‘HHH‘QEIH. 1976).141.? TheWu presentplumsm mappinghm; fig inin the{In Mwatatexwumt1 Mu quadrangleupwuawlu wasv.4: of‘ ‘2 sufficient>“lHi;i;’:lt;1ct.xi[ detail toEH allow.111ux'.‘.l a furtherlulr'iu subdivision\'1ln;i\">»infl ofw? the[1r Kuraseawc Group(Mu hp inM the[12¢ area.“I111.NCV.’“[114MITJT‘lILftJr‘Ili‘L New lithostratigraphic units:1r13:.nl of . . H . . theflu, rank[.HH. offormationsmt inrflmiiufls couldul bem defined,kiL‘lCLiHA as well asa oneanu economicallycomm: hull?nulwzmnr important mem-wig-:1; berEHI ofHf onean: ofwt therim formations{WHILM‘I‘HYU (see:ng table[49‘c 1).

4.1.1l.1.i The'1 hr MugenoMugcnn Formation[urnmrim] is1a theML: highest‘ill‘L‘llt'nC lithostratigraphicalliihuxtrummmp‘r: 911mm,11.1}1cumznnly unit in the area; only itsIr‘ lowumostluaxvnmwt partp411 liesNth withinaxillﬁn theIlw MwatateKin-«Hwy quadrangle,[lihhhﬁtny‘tL‘Blplwuihil\111‘L'ILHHl: exposed on Mugeno Ridge in the[11L northeasternHurrfxrcm. 'n corner1 1mm ofm1 the'124: sheet.nl, Here,llrzr. numerousnu‘wv' us marble11.:T11“5L' bandsMALL with\xt'?‘ thicknessesr1\il,1\Hk” w upMy to[M severalucvm M tens[LI]. ofM metresHm?) L-- are in- ,7 1 n '51' u 1' ‘ tercalated with biotite (garnet‘XUHHL‘t - kyaniter» \ ‘mlxr - sillimanite:11 iHLHlLL‘ - graphite)(wrung gneissesgnrh :7 - and4m} schists, and the occasional bandm of typically'n'pi my white' or buff\wtV quartzfeldsparquart.“ (-garnet) gneiss. The base of the Mugeno FormationI" “I'LMIHILI is taken as the lowermost reasonably continuous marble band on the western foot of Mugeno Ridge.I. The'I‘hc top1m, of the formation7-H Itmtiwzf is outside (to the east) of the Mwatate sheet; it is consideredL‘,‘H~‘;wglj’u:' to be the majorL1" Lithostra-litlu‘mTlA tigraphic hiatus between- ‘rr KuraseKm tw‘ and1'1‘1 Kasigauhwzum Groups,(hmups‘ nowmm" well‘.-.‘,V.\.‘1|H\\.'.‘A known from recent mappingHI.lI1]WiHLZ in the'L Taita[411.4 HillsHWH- (NIEDERMAYRNIH‘1'!"“\1,-\YH et5’ al.,‘i ‘ 1976).1‘ About“\F‘x"v=:I 900" m: . of theflu- lowermostLrum!’ \ ‘ V pan" Ni ofw? the'M Mugeno"Jag“ Formation} ‘ 2:11 .i‘lwri lie within the Mwa- tate quadrangle;'J "HIHK'E‘ the'1; total thicknessm ‘ H» - may‘7 ~ be'- up tov“ 4000.‘p‘ww m. W. Pohl k G. Niedermayr

The type-section of this formation would conveniently be chosen aaoss the d at Mugeno Hill.

4.1.2 The Mwarnte Formation-: is poorly exposed; most of the &t arusin the #I and east of the quadrangle are thought to be underlain by biotite (vet)gneh schists, banded gnehand migrmtitcs, with hands of phgioclase amphibolite~ ble, quartz-feldspar (garnet) gneiss and kyanite (-siUimanite - muscovite -Mu)c tzite. Good and reasonably continuous outcrops of these rocks exist only on the hills wut and eat of the northernl" Mwatate River valley. The noahern tip of Nwni I the best exposure of a migmatite proper in the quadrangle, withirreguLr ohliten& the banding in biotite gneiincs! by mobilized fekic material. Elsewhere, at Nwni, ded biotite (-garnet) gneisws and feldspar augen gneisaes are intercalated with pl drac (garnet) amphibolite. Typiul is intensive foldingat all &,as wellas Gq ted thin ban& of unphibolite:.| in migmatitic biotite gn& bands, the frapentr wing internal earlier foldingI (FI) and later fragmentation and rotation, probably ternponneoua with FI On Zongoloni W. identical more or less mobilized biotite (-garnet) gneissu tain bands of plagioclase unphibolite, marble, thdy foliated quutz-feldspu (ga gneiss, quartz-fellspar augen-, and gnnitoid gneiss. At two localities on the hill a an important band of kyanite (-siUimanite muscovite - Mn ) quartzite; this is sibly one horizon repeated by overfolding. Outaops, however, do not allow a p ve statement. Graphite ia virtually absent from rocks of this formation, except a very minor tent in marbles, and one small occurrence of soft graphite gneiss on the hillTash rth of MLengereni Todrthe north-west, the lower part of the Mwatate Formation characte by thicker amphibolites seems to wedge out between the nuasive biotite gneisr the south-western Taita Ws and the marbles of the MgrmaMindi Formation. The formation's lithouratigraphic eaent is determined by the base of the or ing Mugeno Formation, and the top of the Mgama-Mindi Formation underneath latter is considered to be abow the remarkable marble bands enveloping the Mb {-I Kore ChamocLite Complex. The thickness of theMwatate fornution may vcor J; ly reach 4000 metres. Howoa, repetition by axial plane folding could exaggerate sidenbly the methickness. It is not possible to consider one single section for a -tion of the Mwa u Formation; for convenience a longitudinal section along Zoagoloni Hill to the bwer part, and along the Mwatate-Wundanyi road (in the Taita Hills, 4) for the higher part may be used.

4.13 The Mgnma-Mindi Formation is in contrast to the rather monotonous Formation characterized by a wide variab'ity of metxediments, which in lodge a variety of felsic (7) intermediate, mafic and ultrdc meta-igneous roc Its higher part is poorly exposed with the exception of several conspicuous m bands, which endow the Mtonga-Kore Charnoddte Complex. These marble may be intercalated with biotite and/or graphite rchiis and gneirses, hut witho outcrop data this can only be guessed. No type section can be proposed for the sa! reason. Mwatate Quadrangle 15

The basement character of the Mtonga-Kore Charnockite Complex has been re- .\. cognized by the present survey. The main rock type, exposed in the hills Mtonga, Ko- ' re, and to the east in patchy'I.‘\.{‘f exposures.\'31L'.\ under|‘.II ix'1 shallow soil, is of intermediate, calcd- -. . . kalic composition. Contacts with".'i‘.I|1:1a'\I:!E|I!\'EI-xr.- the country rocks areII'.!'.-'.'.!.(Er\':|-- nowhere exposed;from thege- ological map it may be deduced,.<.'ll,ll52|1|||l\--!|I|\ll'.\. that the complex is generally concordant. Thiscould be primary, but is most"I'I-sl probably['I!--i‘-.:|.'-]\_r' dueIll'u' to[-. tectonicre'. 'I-Il'n readjustement in the sense of RAM- SAY (1967). The internalstructure of thecomplex seems to conform to the defom- tion pattern of the surrounding rocks (see chapter 5). Below the calcareous upperjag-1 MgamaM: am” -Mindi Formation follows a horizon characterized by preponderance of quartzo-feldspathic|.’-I !r]-{-. rocks, including a fmegrained, thinly foliated, white to buff quartz-feldsparT gneiss (possibly a meta-rhyolitic tuff), a medium grained, rather massive q~z-feldspargneiss (could be a metarhyolite), and granitoid gneiss bands (coarse volcanogene metaagglomerate or greywacke ?). These posr ible meta-volcanics are at Mgama and at Mikeli Hills associatedI‘.\E]li.||.'lJ‘."1I_}I.|{Ili\1l'l'/it::\ with a quartzitic rock containing (mainly Fe-) sulfdes,|II.'\. and with marblec bands,|‘\tr‘.\1\.l._[[. graphitel‘.|l:: gneisses'Q‘HL‘In'nLl'j andtu schists..§.\_]1'.:\|.\'. Biotite (-garnet) gneiss bands.'.|'.1\l.‘i and4m]. amphibolites.: mm.- are almost.J'lnmur absent.Ilwcn‘; in theseTIH'SL' beds.lunig. The base of this'i::‘ conspicuous. :‘-::~§"1.;-_u:u-_.\. quartzo-feldspathic.];.; horizon possibly.‘i'bllv representingmy“). ﬁling. a;.- meta-rhyolitic body and its!-.\.‘.'- volcanosedimentary.‘I|.|‘.]'1\‘\'l|‘.1|:‘ equivalents which forms' '.\'!.-ri:'iml1.a Mairimba hill,hill. the tops and the easternL'I " slopesJ. .[nx- of Ride and Alia hills is the higher lithostratigraphic:1'.| iahi.‘ boundary:} of..- theIL; LualenyiI. u.‘: r1151 Member.Mylniu. The base of-?|:1\ this member:' ':.|.. is identicalwithI the base of theMgamaMindi\1g'n111u-Mihuii Formation,I’m IBM? i4 considered to be situated at the western foot of Mgama Ridge. The'1'!:c member[I'lt‘hl' draws its name from the important green vanadium grossularite exploitations of the Lualenyi mine, situated within its higher part on Ride hill. Characteristic rocks of theLualenyiMember are graphite (-sillimanite - muscovite) -1 gneissesurn-Kw.- and.IIEI! schists,\.'||1~I.~. intercalatedEI:1L'::. at a scale of metres or tens of metres.[":_‘x with'\\'|"| numerous'I'il‘ll‘1-||l~ thin bands of granitoid gneiss, quartz-feldspar (garnet) gneiss, marble,I: I; and.l?' 1.....\:.-....I occasional- lyly biotite|\|..ril:' (garnet-kyanite) gneiss, and amphibolite. Small gossans at some localities and\ {I numerous||-|'||||'|.:|'\l- finds1|.|.'.-\ of.ui gossanous£1 float in soil above this member point to the existence ofn‘. smallmull lensesII'HTJJN. and pods of suEdes in unweathered rbcks. In many instances uvi- ties vartlv ffledrill-or! with“1|.“ suchH!|\ ironhvdroxides have been seen in anatectic, concordant pegmatoids - indicatingHir'." mobilizakon ofthe sulfides duringhiih-grade metamorphism. Geochemical assays of gossanous-I|.\ material]I;.;' have shown that Ni, Co, Cr, V, Cu and Zn are present in anomalous quantities (seeFt'.‘ chapter 7.3). The deposits and occurrences of green-'_'_. vanadium'\".’1.||: grossularite known until now are invariably situated-\1L;:\ltm‘i withinw a higher horizon:J. ofn.1' thellll' Lualenyi Member. The lowermost parts of the member as exposed at the western foot of Mgama Rid- ge show a gradual lithologcal change to rocks containing:[.|i:|if;L,|11-.--. more biotite than graphite, L. . and thicker as well as more numerous marble‘s bands.IMIr-_l1\.'|'.:;- This is'\ takenI. as an indication of the nearby but unexposed base of the member.l‘}:'.’]||' L'1'. The ultramaFIc rocks mapped at Mikeli, and.IHI] at.il Mindi occur near the base of the Lualenyi Member; they are considered to represent a regional thrust|||[||\| or suture..!‘:|._ An- other small occurrence of altered serpentine west of Kambanga would then imply a stratigraphically higher thmst within the MgamaMindi Formation.‘.Ir:|s. From1 :-:|I. the" present mapping it was not possible to reach definite conclusions concerning'.":|\<'|.'||.'||' theI|:: mode of em- . | .. . placement ofthese ultramafics.The time ofn: emplacement,II'I'.[‘:.1I'|‘1I!'\'|II however,|]r""\'\|.'\" isI: clearly pre-migmatitic (pre- F3 and F2) because of the heavy alteration of the ultrabasics by acid fluids during high grade metamorphism. W. Pohl& G. Niedermayr

A type section for the Lualenyi Memberwould best be combined of apcofXe along EIW coordinate 9601 from the foot to the top of the unnamed broad hill north of Kide for somt 600 metres of the member immediately below tbe productive grnn garnet horizon, and a profile through Luanlenyi Mine No. 2 to the top of Kide hill comprising the uppermost 100 metres to the overlying quartz-feldspar &s horizon. 4.1.4 The Mtongore Formation is again only partially exposed; it is considered to ex- tend westwards from the western foot of Mgama Ridge. In top t wked by a change in the rodtshancter from the graphite (-muscovite) -rich gnehad schists of the Lualenyi Member to biotitic gneisses. The base of the formation is west of the Mwatate quadrangle in very flat, featureless terrain, and will probably be determi- nedI with-II greatI difficultiesI‘. I' I only.-.\ The available exposures"I. showLuv biotiteI |--. (-Ste- garnet) and banded'1- gneisses3" predominantly,;:I .! : a, with2111:. important'!!:|'-~I|i.||'|'. beds' of marble; quutz-fuldspar (~et)gneissL ..-;. and“.1. granitoid gneiss ue of-.: lessII'I- importance.Ii!![‘|.-!:'.-.i .- The thickness of the membcr represented a- longiI. profilelil‘ A-A“. on-'I the[Inc geologiul.JI,'-'I|-I.-1I.I| mapI‘|-.' is taken as about 2000 a 4.2 Peaology For a petrological desaiption of the rocks mapped in the Mwtequadrangle the following groups are differentiated (however, not all of these groups axe nuppable units in the area): Meta-sediments: granitoid gneiss quun-feldspar gneiss quartzite biotite (garnet) schist and gneiss graphite (-muscovite) schist and gneirs sillimanite (graphite) schist and gneiss muscovite schist and gneiss crystalline limestones calc-silicate rocks Meta-igneous rocks: meta-rhyolites, rbyolitic tuffs and ngglomerates (?) chamockites plagioclase mphibolites garnet amphiiolites ultramafic rocks Anatectic mobilisates, migmatite The weakness of such a classification is well reelized, namely the difftulty to dif- ferentiate with certaintv between felsic rocks of irmeous or sedimentarv, osipia Doubt- ful attributions will be dedared as such in the fotowing. -

4.2.1I_ 1 Meu-sediments\iLIJ 'alallllil'l1|\ ...... GranitoidIrr.;.11r.:.u]511c:~;-;1-. gneiss is afieldIhl'.-I termimm for coarse~ainedmcksof qumm-fddnpathic com- :- . . position,g-- .I: :'. whichatlil. Ii ...occur. In inIII thicklhl- :\ bands:§.i]|.1'~rl: of tens of metres in the north-ma Ridge; thini! bands" LII-i. of--r the||.' me-...1 rocks are ineercalntcd thmunhout- the[:I'L' LdmnrriBLamberii] IIC::"-,-!, :\-IC[Z|i‘-t'1' ofI1: the[EI- MgarnaMindi=-' I.- "~1illlh Formation.IX»: These rocks typic&~I .-."H\ formII-r'i' poddve‘|"'|‘ui[iL'I' outcrops,I. unpa, and\Ll'i-l mayI11 u; ser-‘- _- ve as marker horizons in fddas wellu photo mqping,r :- [pi‘imx .\[ :.' -. :g- 411.! IILIIIIEJI‘HKII‘IE'. : . :u- "..,‘I'. 1‘ "IIml‘i-JII Iii: ‘IH‘L ...(1.lI.II..}-I1]\1|]. . .. . , l - i . 11d: \‘L'hhf'i ‘.‘I|.l\' HEL'H .JI .UIHIILIH‘ |:" l"l‘.\t"

'L'l' '.‘. CC I'1. :u_".k\ \II'I_' I'J'I'I.':.'IIJ]1|.:~1:I la.‘.'\'rII£'I" [[t't'slll'FHJ‘. u If.‘: IIII.:-.'II:]I ' '-:I.-\ putpll}r'II]-|.I-\I~_-"IIL'_V -.I-."Il(|i1 unhulpﬂh II: ' -II‘.I. :II'J)‘I111uuu'l:|n:\.x-“‘ . '|[|i_'|||l'. [“-.' Hun-h. p.n.’._ Emu-J :Ind IIiiL-j. .‘-\II\'|1L' “II-f ’i. 'l‘l ||-'.\'. “hiﬂlh'lllh i-I-w' Il'”\|.' I|I|i.»I- UL. .Ii[ .. IPII‘I'.1".:‘I|]:JI‘I|[ILII1~',T[\\-'t-!_':i|]|:'. _--.\:‘!'

(1' II.i-.I"-II| ,IllLi.\.--L'I\ TIiJ'I' :.' . . . . | . '. I'tih'JK‘.H‘r'i‘lllllhfi'iibl'JI'IlI'I'IT'. '11::1L‘li111.1:l11[:‘" i‘-.‘\'1‘ ii I'i‘ c: I-jl'li'! ‘15:. . ., I: _ ‘ r: I. .ulx 11’ “rpm glit‘lnf‘. IHIII r l'r-;- -.._=i.I.|iI-.-.I.i.I'.-.:.~II In 11H: fit-h: :I' I:I1‘_I E'II'I‘ .‘u .I'..-: -- ..JI":."\_ |.-:-'.I.'r‘\,'u.'. in “- -I=.!I I'm L']‘-C.‘I éiTL‘ HI": illll'l‘ii'. '33! :.‘:tIIIrI. :Itwi‘f gncing mum [u 1hr: I:‘l'T-.'I[]'I{I'[|]!i.L c-gz:ixu.lL-II‘-. ..;'_ l: '.'"|L {£11.12}. Cl _Ii[ cywac kc. [.QIILITIZ-I-(‘ldhpilt' gncm 'Iq s: I:1L'I1'11.IIT: or ‘I-l11L'1:_1'.lll'.]I-::.. w} ' .I a an.“ [whim-Ii [IN k. SHE-SIC ‘.y1\cr.>'}.'!n=.r .I E\lllli:'.-:[i|'-II .I‘. I- .r L.I-:._ In] .a:-. IE.-i!|]JCIif.PIT‘;.-I."-.{1II‘.CJI‘.I.il"-. :tI'IIL':'.Ir'L- » 13-3 .i'III- l..'V'iJE'i.ITj-'.I[1H{II-{EH}I]11.]['{':'-j-I‘tLih‘-‘Ii‘.'[.l'LiI'JI I ': I-h‘I] i -_ EJiIrr;IlH . . . |'-.- ru..‘Hi'!'\a'l'.‘l!. :IL rInL‘ iqlslty. (j‘ldrﬂ'1'clLi-‘41‘MT gneiss hands 111m] surm- I'II' I'm- .rLL-Im'L mm?!» in Lin- Mir. (lll.l.:.l'I1!1\.£_lL‘. .H' KML‘ .Izlci MJII'IUI'IEJ‘J. They .l!‘.i 'Ir..:\i\12l||‘. l-- ww.” ht ‘l‘r'l.' CI‘ I'I..:‘.'k[.‘.l' hurt-{ms HiHJilIII'! .- m ILI'=IIIIIIIIII lune:- ;' .Imi r'I.'.-. HE'\HL.J IIPd.w fhi~dq& (Ip .-III;.‘ '._\]1I-. :I :1“ - In mna b.Bda of ths LPah~l 'n [lI-_ \I:I wcm h omddmabls quurtitks. .n' '|'\ I rIILI'. u. Ith |.1| rartfabion. fp maspedmen from Makiaml, . . lLIHr" ."\I|!!l\ 3mm I-:.'I.'I edges, whichmay be rcrrmnnts of@ -.=I.I-'.-.\1:-.3\:...-I|:rIrIL-ELL-c \'r[|2'\|\"'-.' :u'-._k~ I.\ I_‘_=.. ddrp~~show mostly quadrille sfmcmns; :_\ [III'III 3' \I-‘.|.'.\\ .-- ._: - hbmdwite Rnasd md zoned. Biotite

Siiaocclas'lb tnqsdy Wrgl~ntpturad. Auu- estrmssexamiwiwgaofryp~.

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.I: \ljl‘. I :I I. I II. - i?ICI9!UFC L'IiL'E . ' I ' QILII'IyIis-I. I.. . . .|[| it I- -I' . ' I . '. . '

*- &Ed' h bmc*eis| tWe~lo mt sump$% btored with-. Mimes and. -GBology— Depf.,. l+us&. W. Pohl& G.Niedermayr

horizon above the Lualenyi Member at Mikeli and the Mgama north-slope (P 1015) Sillimanite-kyanite quartzite - as a mappable unit only found at Zongoloni hill (P 1099-1105). although thin bands of such rocks have also been sampled north of Mindi (N 125) within graphiteaillimaniteH gneiss.:H The ironsulfide quartzites are lightgrey rocks, coarsely ctystaUine with‘1‘ interlocking quartz-“L grains;_ ordinarily the sulfides are almost completely Leached from the'. rock‘ it at thex surtan, so thatm. the quvtlite is wggy and irregularly covered by limonitic crusts. In[a addition,‘ ‘ the rocks carrym'. a distinctively poor vegetation. They may be metamorphic cherts associated wilh,‘ volcanism. Sillimanite-kvanite auartzites at Zon~oloniate Linht-nsv. weathcrinn to a vmIU~ local. rer: ‘ 1. lief~~ covered~~ ~~~- witk ~~~ a~ den&. thorn"~~ ~~ bush:- ~ :he exnosed-rc.2 i;&vemown~.-~.~~~~~, &fuselv~vAt~amecis of ~. ~. z~~ ~~~ ~~~~- ~~-- --~~-~r~~~~ ~ hchen. At places, the quartzite contains pods of coarsely crysUUine bluex kyanite.L“. ThcsJ are small‘ individually (up to a maximum of one cublc metle) and constitue} Less than I %of the mck-mas.‘.n." v Quartz occurs in large wins, partly filled with sillimanite needles; sillimanite‘1 M is dislributed‘ w . in. the rock as single ndesand elar&vted bundles of fibres; graphite| and rutile are accessorieg limo-1' nite fills aacks and stains the intemanular matlix. Unt~nicalforw the whole is a‘ swimen1' of Fe quartzite with spessartinc from southern Zongoloni (P ii04), although Fe-rich, dirk quartzite is more‘1‘ ‘ _ common'MH in the northern band. BiotiteD\MIJH. (garnet) gneisses and banded biotite (garnet) gneisses probably are the mostm ‘ widely“gm-Ix distributed‘w rocks in the Mwatate quadrangle. Their tendency to weather easily,.'l‘-[l‘. however,illi\'.¥.\.'L‘I. makes outcrops of these rockgquite the. Larger outcro~sexist only onmm the“’zr hillsMH‘:1"1-- Pusa..- Zonnoloni. Mkennereni- and Naoni dona- Mwatate river:.~~ elsewhere. bands of‘i-l'w biotiteJ11 gneiss intercalated with other rocks have been mapped at Mugeno, the western'.‘.|' footH of Mgama Ridge, and MtongordKasindano. These rocks arc thought to represent',' about.L one third of the Mugeno Formation, more than two thirds of the. Mwatate"7 Formation,:.. Q'gﬁ'mu‘{www.‘c‘y possibly up4 tov 50%"HI of.‘. theI" LualenyiMember,I ".lr H and1H“. more‘ :r‘ thanHut! half2111' of the Mtongore‘.Tr m; m Formation.f Linn. In1‘ fresh5: -' outcrops1' ‘1“ and‘I ,‘“w::;- hand-specimen,1‘t‘,lHH"'- they“Ia-5 are-[v\-.. well foliated,I grey._\ rocks, usually banded by in- lerstratificd. lighter“.‘1‘ and‘.' ‘. darker‘ Stu: laminae,ilz‘H'Hu at a scale of n to tensI ofy: aria.‘ Someu y of1" this banding may well be inherited" from‘ \ sedimentary11W] 1‘ stratif~cation(So or S, - s%e chapterm 5),x while‘ other types are clearlyx caused by mobilizationM 1 of felsic material...x;.v' duriog high-gmde_ melamorphhM r.‘ w' ‘ (S1): Thej biotite gneisses are eseniiallyvV._<", a very._.‘ uniform:1"|ZHH!.'. group“I‘M: of rocks- with1 ‘.H.“'.‘»:‘." little variation m composition. Typically[‘.;‘ ‘_‘]*"“.l (P 1049, 1055,' '~ 1107,Hg'Hn‘IjL'M' 1116, 1145), they contain, xenomorphic‘ qum,{ 7 little if anv vutash1 feldsvar.’ . .- nlaniocksei - ‘ (olinoclase-bvtownite.' idiomomhic‘ to mbidiomamhic.‘L'-‘ twinned‘ add zoned),‘1‘ Gotile,“v and garnit &dish brown, pokllitic; wkm01: an1. intend\‘ . &been observed‘ in' the7-“ garnets,‘ this was not displaced agamst the s of the rock).‘.Vr-‘D Felsic[\ and' mafic‘1 minerals are‘* altematlveiy_ “ enriched‘ in successive bands, to give the banding.'w characteristicI for‘rt the rocks.T - Accessories\ w are‘ apatite,‘ zircon, tourmaline‘ ‘ . locally, and. fi‘ ore-gains.w. .. H Where“U. = biotite‘ i‘ gneisses.- - arem interstratif~ed-“:-'..'. i with " otherr‘ '[wk rock types,"4- the&In v min-{Hull} u} may'1..' vary more widely.m3 At Mgama'.1v they1-_ have‘.-- been--.-- obsemed-' tor‘ grade. intor: granitoidmum gneissw u (Pa!) 1048)1mm and quartz-feldspar{1' 1 p11 gneiss‘ (P2" 1056);W' at Mtongore they contain' sillimanitewl' (I'1080);'w-w. at.1 NmniNul’x. mobi-‘ lizationH ofw'? felsicm material"MH'H' leadsNW:" to migmatite (P-!'!'|"' 1107), olhers aregtanu6ticp' 'MM“".J’H_I‘H 1120) andH‘ contain hornblende‘ (PWWW-“H 1090). Graphite(Juplmr whits\k’H‘T‘JHJLL[1{'|\N'\L and gneisses have been obsemd almost exclusidy in the Luale- nyi‘ZT-w Member ofI theW:- MgamaMidi“.‘_gm-m \13'1 3' Formation, although it is suspected that such rocks form also‘ anM important\r‘mu' w part of the higher succession of this fodon.As they arev very soft rocks. & a rulev and are easily weathered, natural outcrops are rather rare.1‘ Onlv the_ "meissic‘_' and alumosilicate-rich4 rocks mav be found outside of &cd erno- x ‘ V sues. Rockcolours' " \ are‘ buff, light grey, yellowish or greenish dependant on the rock-'. formingI v _ minerals."l ‘ Graphite1, rarely determines the colour, as it hardly occurs in higherVV' percentages.pr) ,1'___H ThreeI ' distinctl varieties‘ of' graphiteup V bearing'I rocksLx canW“ he differentiated,lll‘ll'cILIntwm although.1' M M transitionalF' ‘ V types are not infrequent: ql ,I I |' {\lumi: .1[!n_'i:'

.‘I 1'|:||.:\ ': 'IHILI _ r:.- hu: n:.m\.|_\' pl.u__\_r!n._-|3~.L-_ P HIM-r. t‘n Lm. hurl; u! .J.i}1'r..1L--IH. .J -_'n..:u xi? I.=124:!!1L‘-_L'ru[1.’1:lu “Hit "|\: IllJ;;I".K-t’l .m1\_ |'|l'.l\\1h\':\lL' In hurnlx l! ”Linn: :1?“t \I-IIiUHJI'IHL' mm hm“ ‘:‘.-'-lll.']L'~_ back arnaaoscopamlly.. . .. remarkable knot- _ l-x‘ I':' -P lI-:_;_ i‘ I'_I_~' .- I' If.II_.:' P 1mm, E’ Lil-w kcoesorw-.-.\. - are NW~,apatite, tounnali- :1-.'. I..".-! an “llﬁ' my yum. “ll: ~.|is:,‘. _ i\T\ [cum II‘II: h:- aa frequently and:i_.p- typ~dy-|'.. .,bo- . lJEL':\ [17'Lyr‘lx‘t1ix] ’llill- rn: the\'|\|!|‘.'--.-'\.’|!l'.5 auartzoontent is variable -_"=-|1‘ w I‘L' .:.n';p]-:1c'._r ... '- . II. .J.'-. t!l]\!}1\«'I‘J‘\-'H- - "|II.|'|]i‘.'f||'!- In! Ia; .Ims ephivtr; '{‘.|'\'=\‘U|.'.Ii".' dup-v-iix ..rc-.-i|'.'|'.!"|. I_\ ' 'I‘hc graphite concur in these mt 'is Hmstly ~d 2-5 %;oha few specimen {mm rim mp m Mqumn Rulgic .:r LlamainnmwraBO.1.8Willi.- hare been observed to contain r1|ru:'L-;,_r:'.1phi1c. Uhmﬂslg I‘m. :hue [mu-Ever. r31.“ liyMLr-sr6-hi. 1.1 1-- occur as minor bands or len- sx-s 1m. rizil' Lu warrant furilmr i1:\’;‘.35ip_.itit.u11. TI'C _.'.i"i'p‘hllll.‘ \1. his“ .IlhtgIIKLIShL'R1.}.‘['.‘i|.'-l]|'\' \'€\[|'..il[| mmwr-alwnumerous 'cl'IhIHsmall 'i\-Inxl\:.bands, lenses ur hru's rig]: in Fu-SHHMCS whit cluvulcd 3xcr_a._'lwr:1it_.ul Vulihr.‘dues atof 7Zn, Cu, Cr, Ni and V .:-L'l: Limgltt-r ‘fj. Thia [mirth 5r; tlncil origin u. hi? :Iinuyzlc . I..|')'\. 3‘ :c.'. II‘. \-'. Mn. L‘, (.2 I .‘\:¥ -_'\\'E!JL£PE'1H1. E i‘n- -.:-' . z . . . '.'.H?‘-H1t".1L"‘-'U~!\3 In.” Elude mn- i]11.It':.'-.r‘.’lr.]'~[1i1 an&,I.'.“a:'|.'.\.[!|11\LI'\ muscovite-sillimanite schist,

Sillilumﬁlc [-:111I5cx.svile} s'L'hixt» .IIhI 1"‘11l'iI'L'h haw- :Dm I": 1::i.IL-.'l 4x [- \\i[]|-’J1.|lL‘I LDLk; Ht IEIE’ LUJJCIIE‘i“1(311'11‘C1.'i-iICy --.]J.‘ lJ.||\:.|‘}‘ \.-._+:_'.i-L‘I,l|1_.-_--.‘;-_y.; ,wcl] [Icaiiatm'l rad-.5 r_i'§1:x-i~;<‘ly Lu shin-hm“ .-p]1::.1mn..c. ‘ It vb (Hum! vul'LmJL. 11-1I.JI1‘|\ -'-- t}!l.|J’1;/., :11k;]' [- i\[.‘.!r lI'-'['f1-‘-'l‘.'-'\.I _~-:ml'..xu. 1r1uu‘(:\-'I[-_'-.k\ lr||1\_‘ll11'l.\l ..|1'. x'nrru. 11‘); '

4.2.2 Meta-igneous rocks Meta-igneous rocks within the Mwatate quadran& were aot asaribed by earlier investigamm. This is in part due to better o~tcr~~~e~aod.~lftor the prospecting and mining boom of the last years, and partly to a dBhrmt iucupmtatiion of the orkin- of certain rocks bv better methods of examination. adt& - kceof science. Even so, some of the following anributiona of rods u, the mefaigneous group are still conjectural. This is espedly mefor the f& mchr, whem gcocherni- cal methods helpful with the more basic rocks are less dsdrtrr. ~eta-rh~olit;and -rhyolite tuffi ye thought to be repreemtadby the quartz-feld- soar. -eneisses of MaLimba. Mikeli. and Kide. The mela-rhyol~tes(?I are Light, massive rots, form& hnnmaat aahml owmowi. They have Branoblastic or gtanulite tLhue. Theu main &itu&~an qaute (Isainly x~nomo&hic, .olatv: .. sub-~diommhicmains with embaved. rounded odnas oc~m.be): rllultf4dam1(abundant microcline, orthoJase).plagioclane (andknc - ~lbmdohe;Mmed ;hd zoned, cbrrohod by al- kall feldspar), muscovite (strooply altered, unslable), and biotite (m).Accassolirs am rirmn, N- tile, apatile, and opaque malter. Spunen attributed to thhpoup am P 1095, P 1130, N 123 and ..N t7A Meta-rhyolitio tuffs (?) are whitish to buff, tmy hmiwW mdihouppe4 at Ktdc (N 122), Mikeli, and Midi (N 126). They show granoblPstic to gmrditie tax- withxenomofphic, partly platy quartz (large grains with emkayed edges rare), orthodrse and miixoclina, plagioclase (andesine to labradorite, twinned, pady zoned), biotite and muJEaite (tlw latter pale grean due to a certain Crcontent). Acasories are rutile, zircon, apatite, gn!phite. and opaque mat-. Charnockite constitutes the hills Mtonga and Kore west of the Mwatate River valley. There, medium grained, well foliated, brown, andvery uniformgneiascs form conspicuous boulder outcrops. Under the miaoseope, these mdrn show ganoblenic texture. The mineral ammblage is quartz :alkali feldsgar - plagioclase - hypersthene - diopside - hornblende @ 1083. 1984). Quartz is subordinate at about 5 % of the rwk. Both feldspars, alkali feldspar (st about 15 961 and plagioclax (60 %) may be recognized. Alkalifeldspar proved to be orthoclase, commonly perthitic with Ti; braid-, and string-mioroparthites. Plagiaclase is in the rangs of oligoclase - bytownite. twinned or unhvinned, and partly zoned. Bent twin lamellae reflect post-xystalline deformation. Hypersthene and diopsidic clinopyroxene are grouped together, in about equal a- mounts (5 % each). Diopside exh%its occlslonnlly distinct exsolution lamelhe of orthopymxe- ne. Olive brown to dark olive green tsch-akitic hornblende (6 96) sumunds clinopyroxene in clusters arranged parallel to t6e planes of foliation.These clusters may be remnants of maticphenl~ 21

.-':IL'I'-I II. aq%&ikua~aWsslm-up to about IIl]?|'I\1|I-':.l'kprcmtedintaBYeI” . I.I 3.I

N i \'| \ 1 '

‘1‘}. l _3

4.": _‘-‘.

:1 'II‘HH I'|_ -.I_I .‘x1IIH III] - n#'.‘.IJ[ dnarmiad\LI‘lI_':||i1I:\'.E - i-;.I,I 71.1] 'T. I.-: II. .‘x..»IJ FIJIH'} ‘-.'I|' VTIJHI PAL; H.171? III-:I III 7 IL}; i;Ti_]I1:1\ [JIM Uﬂh II 3h '|,I.1 c1- 1. :IIIJihllllL'.

VEIr-ILILI 'E'Jl‘jq ".i'|.rIl 'J'v' hi] '."i_ '5.

3: {I 11lL.i|I'Ji}]i1|\.H'i[ _i}1731'I‘Z'iiEL“_'1.lTI‘.'I[‘IJ"' I ll 7-1 K '- 1': _.I'I-.! N 1 ‘II JIIIE gmmllitu :'I\' 1)::- [Ir-n: I'*-1<:=‘.II;.I .mIl KIJIL' Hi]: :\~.~.i\'cI] I'-." 1hr [ljl'tL‘lh .1'. l_.|i\r::.I:II| \'_ MILI- iI-w -:- -. I. ] ljl'i'Jlil -=I' NahrI'iI'a; An [1351. thIIimku

'] Ilt' prI-IIIIIIIEILIHK [IILJ\ Inn-41 MUM-rm 5’ 1I'I.""I -. .[lhlil]5.mil@ BeslII::~'=: hckswrnrl w- Ihn‘px'rnxunti. 111.“: L}'II:I'-JI{'.11KIIIL‘ _l' 10:43 ﬂux; = Il-I-u &~l..|'|\':I\C‘ TlB rorin &+.b I" .:| Kin-mm {HHIIH 4m .1115“ linu. 1n 1hr: = 'i:{' --17 u hi-. kI: mmI.I- Ilr' ~~~dwlprnomrtieIsl iv .l‘ .-.I-I .I III -iI’|l!I1'li.L ‘IEEL' I'I-L ks l'trl‘u’L: been humplcd. |'- In II'IL {III}; I\ Vt]; {71-9 gum-n1 -'l '||\ :‘r ‘I . maul}; ]'

_ 'vIgI-;1'~i11L':LL'.p.11[1_\- cll- -'|J.1‘l , E1: Ilnhlumh; 3.;1 . I. , .. :n' El'l\'|L' pa‘x 'L' M“: i ,'I‘.'[H}]|'l|"ll . I- . Ii-IrIII: HII'IIL'IgHrIxxIP lI'IaJI‘ nltlul'llnl'¢*lr . I. r. '-'.II :‘|1\‘|"‘[P1”1\)h| Hil~ \'..ILI]II1-ty n! :hu Ll‘l“.[‘|-.'-I‘.i--" - IIIIIIIIEILl'H I~II.:‘:"I.T]1c:Imhc-:h.1tn-\IE:i1I.-niPlHH“ |.: {III' In lll'l m- }; Hid“. Amphil‘ulitcs have hct‘n map M! with}. {'1‘} l--'-.~,‘-:I P.i!1 -.'-1' iT-" F :-III'I.-.I"II-I: :II.LII:]}': [Eng-I .It Lin: hill» NJHE'L'I.5h1}\€.']1_ﬁL'I'L‘E'JIIJ'lhllz/Jllll'iI'll)": ,WlnyamOf&eL*frg.I-i | Int-52‘ ':l L}: J:'!;L])' ‘I‘-'l'|||!Cd. {‘fljidlﬂd dri]p]1i‘l‘--= l iIL-x l!'(’\\-'l“1'lll'\. ll l'!:LII \L‘I [IV-n. [hr-Ir I'--I,'k- I‘i.'-I' | I- :' p . _L‘J-I I.I'«,. pi "-i: I.-.l. . ..}I..:.:'» I-‘ ‘I . = _ ' 3 -' I -\-_'I‘.-I1'-a | . 'l'. -.'.:I-I' -: ! 1| I._

'|" !| l' [I'Ic‘LIl .Inmy: n1 EwII \.J1‘.1‘,‘-‘|.c\ E’ 11' L. l 11%)| 1"“, of'Ii‘. wxp$ibolitca| fScwl I NwiN” um: are I: '.i 'I. .-.|".:I]II\_" l}[11l':1'\ i!) 1.11.‘|n.' 71. 'I II‘I__Ii ‘. ll II'~I ofHI Wid\Ii- ..:I'.- Cr ye hmted. I ! wan i . a- 11:1 .il": igner.-u.< I-:'_.:i‘.'. --1 rink.“ :r- mg?” ,-\I \-€;_'.:r11Ll Ridp. Amphﬁa .‘Illl; 14113: thihop to a few mmrw re im- ixi lw Hum? '1” Slope-ma H‘III IIPlJH' ”1' :‘I'll'aif :'-I.ocksL- are.II; ~argfprcaadsmatl, ss they -!I, I‘r'-\‘..l: '.‘ [21(- baa-c [Illi' i.|l.ll:l‘[|‘.': .‘~.1-_ ody, which meam at the sme time. ‘ FFF F

theF western[ footFVFF of theFF ridge. Here,JIF F‘ both‘F‘F, plagioclaseJ‘ amphibolitesFFFFFFF.F1<: andF garnetFl' amphi-F1 bolites‘F have{n.F beenV found.FF Uddw the microscope,[ the garnetF amphibolitesF ‘ consist of' plagiochrH FF (OIigodase, FF'F . - mdesine,FFFFlr-FF twinnedFF F F and, .. zoned),FFF idiomorphioFFF'FF'FF FuFF‘FF toIFF subidiomorphicH FFFF‘ tschcrmakiticFFF hornblonde,‘F F 'F andF paleF‘ reddish-F ‘ brownI VF poikiliticl‘. garnets,F plrtly' with indusions of hornblende, zoidte,“ and opsqueI mattu‘I in pt' rallei1F arrangement. OnlyH'F‘, opaqueF F matterF F was.F obsenred as an acwwryFF FF mineral (P 1029,F““ PI‘ 1060,Fq P 10771.F F - OnFF the base ofF~ trace metal» values (tablew 4) the Luulenyi1F amphiilitcs are thought to be derived from igneous. FF material.FF ’ F A‘ hornblendeFFFF F FFFFFF gneissF F foundF FF: onFFF thedumpFF FLFFnF of anF excavationFF.1 F in.FFF theextreme~. . southeastFF ’ of theV, sheet,‘ (P 1091)FFF‘ F isA probablyE FF F meta-igneousd ‘ ‘ also4 in. view of itsy highFir-l" trace metal- J values (see table 4).5 ThisF rockF consistsF ’ of' (quartz-)F ,F plagtoclaseF V1 F - diopside,31F [~ F whichF'JFFI A is ma-l? inlyI alteredFF F FFFF to actinolitic' FIIF hornblende,’FF‘F‘FFFFFL calcite,FF F' andFF,1 zoisite.FF],FF OnH,FiF the dump,FFFMF} itFF wasV-‘F assoc-F . iatedI,IF'.".“.E‘|F~,F1[“.CY with g~et-biotiteiFFFxtr gneiss.gm 1‘7 Ulamdii‘lFTJIF‘FVV rocksFFF-lm have51 been mappedF HM onlyF‘ at‘ Mikeli,V1 Mindi,74' FFFL andFF 1 to the westFFF‘ of Ka-HF mbanga. The threeV occurrencesF areFF allFH situatedFF FFFFJF inF the5 southern put of the Ldenyi Member, which is moreI F F1 meta-cdcareous-pelitic[‘F1 F F , ,FIF My ‘1 F‘:‘F1F!FF.] than the northern part. The latter con- tabWm more H v quutzo-feldspathic[F FF [:v"l V‘Ii (meta-psunmitic)[FF | F’FF horizons.FF'

SampleF‘FCE'L, No.\Qm. Rockl-‘mi Ni Co“F Cu(11 PbHF Zn Vk CrL'

P' 1075'IF ’ Amphibolite"mph, Fling 1000‘FFIFFF 125F,” 20,‘FF 100'FFHF 90‘Hl 400AIFIFI 485'FF. P|‘ 1077FH' Amphibolite{HF {'FFFFF'FF‘FFFFJ; 10001mm 125F)? 25 100IFIFF 80wall 35057w 410-F‘FI P}' 1084FF Chamockite‘ 1000[FFF‘H 65g": 20k‘ 125[‘7 80lF 50 280‘ F P[I 1091FF..I Amphibolite 1500llFFF 100FF‘FF‘F 10W 100FF‘FFI'F 100[HFF 200,",I,.I€1F 4257113 PI‘IF‘F 1114 Amphibolite 1510lﬁIFF 11512F 90FFF 85 140HFF 1100HHFF 500mm P1’ 1119“IFF Amphibolite 1500‘13‘11‘ 110H“ 88‘7 130INF 165FM); 1240lib“ 500:FHII PJ'F 1127 Ultramafite 1100FFFFF 105\FFTF 63 83 115 170 1200 P| 1131:F Ultramdite 147511757 70F‘ 85 185 145 290 2500 P|’ 1143FF F Ultramafie 700ﬁFF‘ 70FF 135 123 95 210 1800 N. 130" ChamockiteK F FFFF ‘FF 400JFFFF 65 10 . 80 80 50 - 90 N 131 Charnockite( FgggyF F 350Fm 100‘FF u) 100 100 550 150 Table1,: . 41 - Tracem metalr J.FFF:FF1!FFFF.FFF=:F;F'~FFF:~ content in metaigneous rocks of the Mwptate 1:SO.M)O sheet area,FFm (AAS"\‘Vw assays4- [\w after.FT: ’F hotEFFFF leachingF'FF:}F‘FF1; in71': HFIHCI by the Chemical Laborato- ry, Mines and Geological Department, Nairobi - Analyst: E. P. Mwaniki). In the field, ultramafic rocks do not form natural outcrops. At the locations cited they could only be observedin prospecting pits. As far asthese erpmesallowed, the following obscrvat~onswere made: The dtramafites form iew of rather imgulv shape in graphite-sUimanite gneiss andlor schist with bands of quutz-feldspar gneiss. They may also be in contact with marble. The size of the single bodies ic estimated as varying between 10 (at Mikeli and Kmbmp) and 100 metres (aMindi) of the long axis. Contacts with the countty rocks may be concordant or discordant, in an cases vivid chemical interactions along contacts during high grade metamorphism as described by POHL & NIEDERMAYR (1977) at Mangari have been proved by field observations. In handspecimen, thew rocks are dens, nonXohated, ofgrrenish or yellowish brown colow. Under the microscope, they prove lo consist mainly of orthopyroxeae (enatatitc - bronntc) and edenilic hornblende. to mmorquantlties have been determined in rddition: quartt (P 10971, mu- 23

v3.1 41' I“*‘ l'Hiw 1'\'4‘w .. :11‘4‘.::‘1“xw:'k4 {.L'. 4\(N ‘412),_‘4 Yomc~pme-. l :4 "\(N H127)x..' und4 spinet,' 41’ El ‘ I ] ﬁnumlh, -w'.:1;..":;‘.:'H~ uh.“- H": .‘-:H_- ‘L-l ‘ ehy‘my m.MiH ' 4 an" d&tmWlt7’4‘141‘2'w"’ | a. L mnl'. “w ,- ~m i1 angk‘ hwy ‘\"‘.1:\‘."\ an4:. -ibed 4conreatw‘v .4 inz '\.rNi, #Co,4 ‘Cu, ‘C ‘H.‘L HS 34: -1 . H 4“ is UJEMM‘: 4 7f of' anigneeus m: w ' origin of thee any LLHELILIEiHHS {tum l.UHIEL.l'4"I"4HY‘. a" slmilDI dtsfrma theTai- n._“u' Nll'il'.3l.'.1“-.'\1:\\'R LT. .41.. 1‘73; 4'“: Tum. 41% (POHLI’H‘rH &A NIEDERMA%%,".ll [ll |-"‘.’4‘-'.':i ‘ t!'l’-.‘(' IUi i'i.‘ {TL-l" I'lﬂv‘n' L“L‘_ .4i4131':T£‘\ \l T)": I‘.I;'_1'l_' andH1 i ~rolctnim2” V '7! origin&,_1_ 4' V|\ .:!I;-rr43 [1} 3411.114 3.131: rm-MHIHHVM‘.-:"\ dud g‘k‘h:"‘4=':\7ht 1"L'HJMM&titiesolutions [41h r‘r Wto "H.thet' [11-.'v.'."7 .~r..1:-.-.‘i'14wc .xln'ntiwmusiu} tTLVA‘Yl‘.’;“I\' uh}: 4_-HEH’I‘. rocks- w -- mayH beM- summa-Hm!

Iv-wrnmﬂdifwn siliudtﬂu; Imuimliml. 41141 .4 .411x‘.1t1rm~f the4'uti_.;in..lminnnmdi; inw.vm«1v:uk. .4'4‘44 4iu<1llLutir111,.nmi um i4 lumen! in Mg Jud (Ir r>1- :iw mummy rm. a At ‘Jungmi. (”h EJIL‘»CC~':~ 164.1 ((1 [Etc 1'4‘t114.l'ir.~:‘4 44: .MUILcorundumrm (ruby)r'IUy and4m! 3'}*._'L':§green Mg-\WL' ( r-[wna::'1|:.|lincs4 lnttJituHim.4lcpf'reii*‘-_w!‘.n'4rhrmhu'11ih‘.gn‘vmrw'n.1'r.'cHw-aMIHhylliteashtos have been produ-

In 1111- ‘\.me].i M1..H\1iL4‘H.ezz:4‘4.~. I‘ .: minumwt'im:‘z..:v.u_-:~v.-u1.tw..:.u:been found to:4 “mumcontain tiny1i'.'_ Ul'dE‘h .11 MIN. gt'n'uudum 1!‘_11"‘.'4 [nilmf‘lfi <;1].1‘.1{' Unfu‘x‘,hinllhowever, fi‘fln‘r. have.HHL UH!nor yet\‘r‘: been;-.‘. h .53.“ . -'.t {CL}.

1.3.3 Anulcclit Innl‘ilisulca. nupnmtih‘ [123.244.47.1c 1114.4.1murpnmr.4.4‘n94iv.-.1\Ic \:':\. mlof felsic.‘wlu: rockr4 - mar-J11:-constitu- HIM in [52c Vim-Mute41\1.uir.x:.gic.

L-‘A 7:. mv {MElli:arcmignmmmmzxwllmgu‘glrmrrn‘i“main”..‘x-.|i-1-4p:4.--rz4'toid bands andveina present ini-. all‘H -V‘.il'.zlv|¢_- r.:-._'L.-. ['\;cpti4_;11:. .II'C‘ :';_n_']-_n ! .4. Lump math-Hn &g{AA-.4. I" them resistant against to- MI 4.1- partidl ”wiring .11 the pr-mwflitinnt um ".ed (ulnamafic and metac~ureous 'yvlliphllhl‘littffi. C]U.ll'f.".[L‘§, ' I'L. ,.i]‘.4‘: I'H'Ln'h ”41V“:the roe& of the Mtonga-Kore Chu- Azfu (Inmpicx. [JJHLlL|‘.'1<'I‘[‘ilil’.llll~l1‘}i-\HHL'!CIJII“.4 L‘1HT'I\I.K:T v :14:L 1n m . 44'1JI'i4uhxions 4mm.and H20-pres- "':|I'L" H44 .1 V'.1"1C‘I\’ ut Inrfiwlhmh: ethc \q 44' 1t: .T‘imlkxw‘: qumh' winlctx I.!l!dl[/-}H1(d§i3 is] [apu-plgfixwimp1)::‘44i4m1ixwim'rtu.and d&ts (,,pegmatoids")”Dear .414 4| h" \nl'.‘1‘1.I[1>}}t-C:k\ia}‘.lr -}.~i.1;2m11\4‘ chum up mm? '4 .';1§.1rr?-pr\r:t~]1 f'elxlspur-mviscmitv.‘ Irma-Hui: pv-gmuirm'tes (penetrativep.111.- over larger..|.~ -.§i.~.€.m\'.£'§. graphic Enlvrgnwth Hf qwmrir MM hflJHIME: Quartz. vuinlctu ‘F‘_.HT m.1i:11‘_; in UP» .zr wflwn ,‘I‘v‘weirsesw andn" schists4 Hi 11w of‘ the'M. Lualenyii .4. Muml'vm‘. Ham Arc). y~ thin ‘W: 1. rim: _‘“ cms thick)[4‘4 - and‘ relatively'4 v shsnI lu'llw \ :1' 1C: \L‘Vi'rxl] HH"T('\‘1C’.‘_‘TV‘H . “"1’1“ 4 H’ 4 \1-"' andv3.4; folded as well as discordant I1]"‘"‘1-'.. ui'm‘i'llch. cutting F2 folds.Th- «we, rl'm mm“[I :411 1'4 4.1743 . of such veinlets exist in the area. In additi- -:s. .4 ru‘ :_4‘ EL. r‘.,:.[‘_': trunk-1. ve diffuse margins, white the supposedly la- 1w mum ~in-w ‘~llllp1‘(VlJ‘}‘.l§"' ,. (311.1112 ;-]ml;l~|1 i'vzpal 1‘].4gi<44_'1.4~4 Injumunwlxpegmatoids are ubiquitous in the biotite _'.iI\-Iiu---. 'I'j.‘pican_\' ”My; Mum 1’41' .4rdant14% bandsV‘ m ‘- and.- 7 discordantt:- 4! veinlets in the 4 4 4 4 z . - !l4_"\' ?Cw'“14_‘x’4 .“‘H".L‘47‘_"'.K.‘4 ‘.‘. chaptet4‘14" 4.2.1). The structures of these pegmatoids are very variable, reaching from simple unfolded bands throqh shear- and now-folds to pry tic folds and boudinage. This indicates ldyhid differin conditions of de=tion, probably controlled both by the nature oft1 e orqdl rock as well as the amount and nature of the mobhuD&ac and sharp boundaries of these rocks todthe unmobilized bands have been obswd. Occasiondy, a loul enrichment of dark minuah (mainly biotite) dong the boundpries is very conspicuous. Quartz-potash-:|i.i‘iu ieklspar-(plagiodase-)FIJI-1‘11.“ Illr‘i.l{'_:sl".'|.]_‘I-C- biotiteIT} (game)"!'|1l.'l! psgpla$oklaPUEI'ILHUIII.» occur ewntial- I . . 1 in the same\..i.._;' way\'.'.£\' as-.|.”‘ the[:I!.‘ ones"' -'" just described. They|L‘\ show\IIl'JHr" how|‘.I' " 'I me^,"" a tendency to :1 | Aoud earlier structures in a diffuse penetration.I'. ~ccord&,.’\-'|'(H'-511|L{l'\.'. they' M:[L’ hereIiL'E“. connide- red to be a later pe toid generation.:.-".-"1.!‘i.-i‘. TheirIII-ii; dimadmu.III]!:“-'.-~]I"Ii‘- arc..5.'- hquently.I-‘.":‘I_|‘:]-.".iI.'|.\-' E&&I«int-I .:-r to‘, the earlier pegmatoirWhcre thisi|:j- itllw of-..-| mob~tion1m‘.-:‘J!i.’.lli-:)I| dt(i."L outcropacale, L'i'tiP-SI'JIEI. and.m-l " . . I ...... ' -- .. . I _ | earlieri's|'|"-.‘I' structuresS'.r'\J-_\I. are.!!'.' hardly£‘.rI..'l:J\ recognizaEr‘. "l:|.|.’.l[‘|t.‘.T le, theI.|:' rocks'. =\‘\\ ace: L &dl il; migmatitesHmlilrrn inin thisIN» re-rc- port.]'-:_ fncluite besides mu- .‘...... l: ‘ |_.| I .H _.=_.. =1. 5;]. ‘. .. 1""!- scovite.\\--\-1I.. and:.}\. green._J-.LH tourmaline,'.|.'|Jrl.1\l inL. bothIIIEI due(IILL toM- the”In &en&LL...I....1. '. Blgh.| gl we_-..!]"_ metalJ.JLl.s background|-.|L:\ in the country rocks. Locally, they may contain pphita}‘.-III§L‘ in1H largeIiil'gfi.‘ rosettes,Tux. ah& of dimanire, bluish kyanite, sulfides (mainly pyrite),I‘E'iitr}. urd:amI nuile.:"-.:‘.iln.'. Very\'-;-r\' often,when.- a quartz- core is developed, or quartz-veinlets cut thefIlI.’ Paglimiilr iadicatingin ".I.I.I a late' hydrother-‘.'I‘.'II['I‘.-|.]li_'[' mal stage. The above mentioned late quartz&\E-.|\l}-LI." '."\!I!'. cutdug foldaIt'll“ and othu..lllm earlyL'-lI'I_\' structures may be consanguinous51103:; with thbI'llis poa-ppakicpm: " quartzdeposition.'irl:x'-LIL'J“I.-Jh. At Mtonga Hill pegmatites cut the feh cJ.rcr in the corew (Ill-(- of{:1- the anticline, but also.sI.':"' the1i}:- mainnmit‘. charnockite-_'I!.i_rnr>a'kirrs nearmm thethe northernMOHIH‘FII &t[31:21? ofmi the7. - hill..".l_1’m(‘n.urur. Both are rather uniformXIII-I. rr-I in composition,- ”II-””4"" consisting of lnrge mkrodinemicru' porphycohlaatr,.‘5.l>[.\_.\t‘1||l:pl.a_\_I_i.I3"'.-.1.\r_‘.CELIA? some p&odase, quutz,(1'. and: magnetite21i.1_,_' in coarsely cryatdine pockets.‘5. The northernHIHIIIL‘I :1 pegmatite1!|_':_'i|l.l'\ can_J.II beL”) fol,[IN] lowed more::.-Jr-- thani|‘..=.IJ 100 metres dong strike, at near veM‘.i{'.t| dip, _ and on!.:| swage..\'L".'._ ‘Ilzusi 2 metres thickness. It is thus the largest pcgmPdze Ken in the qudrangle. .. . , . . . MigmatitesMigmnlihm develop-.|C‘.'r-]L‘-p from? banded-.m.'.r-\'i gneispes,D1015.“ wherewen-:9 mobilizationll‘;-"‘:“.-||'.’.1E]~'JII hashm. obliteratednl‘lncmtc‘l ear-em- . . . -. . .' . . . . 1 |. lier.k.' structures'3I'1'Iil..'TlE]'L'.\ som1 &,E'II. th*[I'm-.5. naithaTln'llila'f the[:lL' wel1.l‘|1‘.{{:l\iof the TIH' original'..I|.‘L'_]|"..1: rock\ nor301' itsH). banding|‘II‘.1||.|]'|J_.,'_ is1" re-IL" cognizableiFJI‘IC exceptL-ru L'E‘I in5.11 traces.1t.1<:L‘s. A largeInge outaopI'JiiI-.'T'|i"- of +tituillignmtites iais the[IlL’ rocky northernnnrllu‘rn pro-inf-.- ' I ' I - : moniory|.|..uLu..-1~.' of Nmni."\J.u»:‘.=. Hill. There,'l'lwt'c. generalgum‘m! growthgnu-ex: of.-_-.1 feldspar-bkctsICIkIHI"J['--1‘Jrl.‘~[.‘1 and peneuationpa: CLmUt-‘z byI-x quartz-feldspar-biotiteIIiutiln- mobilisatesr11:31":i]i5:1;cs has11:15 created(fl-.110} ,,n&ulitw"..11c'L1I'.[IIL':\" (gnnitoid.:__.::.1I11'T.n'-' =. rock(”Lie with nu6c15:..Iit' schlieren) and ,,granitesu.\-r.111i1L-.n"\\'ir];- with hypidiomorphic13'; IIiI-L. ::'[.\I|El team.I'vxEnm. . 1 Similar.‘iil‘..ii.1r rocksr ES haveIlil\'L‘ beenIJCL'H obmedi"‘l":L‘I‘-'L"L] inil. wPllcr:\!|i.'iIII..‘|.' outcroU'LIL'CTK'JEJI‘ a elsewhereI" '.<_'\x'£’1<_-:'L: at.H NaoniEmmi andJntI at:I.’ Zongoloni7.:rn,_-'-.'1]s.u;1i. This pattun}‘.i[u’L‘r.'1 ofn." distribution-I!.~"_: truth-:11 ofnt' highlyhighiy mo&dumbilisuf migmatites1::I;._{T[1.iLI[c‘.\ isi$ huehere inter-Intur . 1 _ . . pretedrpm-{v.1 isIn beingI!\1'i"]:.-_.‘\-.IL1<‘. due to1m local variation of pt,;. pH20[311:0 and.|n_'_r.':1c the compositionv-nnpc..' inn of[IFEIW' the origi-Hr" ' 1111|l.1I rocks.[-3. Ln. A.-’\ systematic,-_\'.\'tr:i:‘..-_li-._ regionalI‘. '1' pattern}m[[em ofuli higherhigllvr and.HLI. lowerIriw '1' temperatures:r‘lllp{.'::1t1'.rr::. reachedrun. cannotc.1I1u- I-'_ beIn. implied1 JEL'LJ fromI‘lllli.‘ thisIIIJT- observatiou.Oil‘fit'f' :ilH]. OthaIIIIllTl' highly[My mobilized{:1 :Pilé'xm] rocka1m I i include the ..'..‘ .\.:.1.. ...»'\I . '. .‘-. |.. granitoid'._'_{u\..lL-.\.u gndsses,_._"Hr.'::w.<_'.~.. somev.11”: banded{LLILIILI} quartz-feldsparLlllllIEI.: 1r_]-.1\|.‘«.u gneiam,hhcn. and.-.HL: theLIN! almost.|.|.J'f"\L ubiquitous .:I'. ' banded‘2 biotite'l‘intitv meisses._._'_!1i.':\"\I.TS. As'1" mobhtion||:1'I511i:-..- of the tkn ,,mipatit;"..:ni;\:r:1..[i1r:-" would'.-'."‘.il:I] only-.\.']|I.' leadIr !I| to confusion.\ (I! I ItI was'-.k'.|‘ therefore‘I'I"It‘|-I!'I'l_‘ restrictedIII..‘.\?'i"I.'f'-.i to" the rocks described:|\_]';-(| above._|I\.".\':'. 3.5T1'11L'Tlliu'n

1w1-m 1‘. ”IL .\ -=:J.n.|:‘ml' rue heavily defmmcd. As a .l I: 1' l '.i--;'.aHH~§'x=IiI. ].i_\.'-_‘IE'I..'H‘ (l‘- r -~ WNHW'H ‘ , M 1“ l ‘:';-74Hi~-\;'.iun EE.‘_\|..:."\L!'I"E_lk_l"1-‘|W\:_ ;‘ m m X NW. ‘E‘:'.l"“.'\ﬂl\1;‘}1:\,".: “1‘!'I.I_“\f'\";‘2\“. 2W 1“ I. 1‘ ‘ I1 'AIJV‘Lpili, fxil um" .Hh'" kn \“J{L“

P I ’I." '1IL\ w H:‘ ‘1 a". '.;..‘\l.,nr1|“p|w..m.w w H‘w ':‘ W]: }-_ M H m }‘.II.LLIJL‘,_'LH.HU\.JL‘} .41‘:"\:l‘.r.'|l\.'1 [h LH Hmni r w: i]- :y---r‘-‘\-‘1.Izin[_'{-l-r'mvwic, _-:r.:.1- :zv. 3' " xxwfl‘ 1 'lwm'im r"-."'I HIV‘ twfl'ilit‘y w? 1::.-,H} ' 3p V.- l'. i“ Er r. “hm; «MM ‘1‘“; -1‘:“~1._-.\L“l'uxl'. “L“J_‘I\-L‘_€.L 1' 'IH'H 1".L' if. I" i ‘ ‘1 ‘»_" v'.‘ H | uwfiumu ixVIv_'"'H|$‘.'1">H}‘VJL"1‘II:L"'M'II- :1: .iul l" x. ?h Hug‘ A :‘m ._-rmpc{c-:1r beds m 631M: Iv H ;.~.|Lm_‘_r1ci~ss.mc_ Jud 'pc -rmln‘i.i \m'i. . ‘ . KE'V‘K' \“..H'L‘ .L Hflt'ihni'll'!I'IL'Vt‘JL. '.£\H| 5171 _ ‘smmctrik HI njv'mIm-Hh u-‘- an L‘ j, H [Him :v‘mimg .am! \\'l-‘I.t“-;‘I'".hl ‘ .17.: |.w{:<. 1'w 'm_"-' (1r;- nH'nnyh Mir .1. I": w 'i-_\ I‘m-=1 _r- vings, theI1 axexx. of minotfo-‘ . EL _‘: raw p11 [Hui L]!:HHJ"iHH 411-14: r:1:- .1n::_ I..-»:1'.Hm .3 The heatibn1m H is a b lines-H' . :1'n .H'.‘.L[='.‘dli?\‘1‘<'lill I", .md ['3 I'ml‘iu. i win ‘m- appuvnflj.’ nut A"':]IE1:'.VH in. Iln- mam. .tM-H .. thir may‘ pnnlygm: I he dueV‘. to* '=, ME-v‘nlhl'upx. H‘hnfl"; 'iimmr {tulinrvm l-li‘lJ.‘ Mr.- .\1‘.‘.' “1 m "1 3|. Mf‘w\1“_“.1i]].lliu_‘_'f.‘. ”my In: xi‘m- m {lull-film; It! ‘ 1 :ME “:1 of‘3' lithohorizom“(FM-lllfll'i/HH‘3 across_:~':‘ u; thesethe“: Ec'ulllitL-r‘ it] (11C T-d' : “Ella 1.“ -'I IIIL‘V yifL' I‘K‘MI \"-.Pll!!)".‘\{ .i‘é fl'1[1|_"5 I31 lln'HL‘ Ill'HCHHtI In _HIH"~_‘ 1'1'M1'H‘ r10.1"»m:“Um!dis;.»L1u-:nunL

FM} I|’1d\

Hw Mm. 5Wi:1.i;k11wLitH‘u».htz'crcntnLcaliv; If‘c \twmxv. am; w w |\ "i>;\r:,:rr.u{ lh TEL. :.'I-]1\'\'.H'L' ~31 F qTiIE'I \ ‘5‘ ”my: n'r- I'M-uHim; .*\ 'JHJH :Apnm‘l --‘-:.|1‘:ir‘; m , 1“} u\‘]H. m. 3'”. ]_ ‘ 1.1- i- wlwrmimzul in 9;- 1‘. Uni "H twp. .1 ‘ L ”\Hu‘ “w , “lbw ,, "L‘1i‘:w(1‘..H-lllluiHhhfu'd? m. xx} :I'.’_z_!':"|-_‘Z :-:-:1 u 'H - r ":11! 5‘ m 5 3‘ {11“ w ,. m .mm m thy ~:c:1,_1v.1:..i Ian'ulqi I’ \ [|\'-.-Hlnm:.[ In :x‘mtmli‘cm. Elfin .-ni.l.\.‘..|' 3": " W’.‘ w "mm v \ Tmr‘ I3141.41hun'Lt‘LIyesterly strike*1" 2k): areJn.‘ theC1H.‘~'il..i oldestfl\'1.uli_‘llrr ' M lv “ v , 3' 7 m V n “I [ foldw Tin-y mum' L'vcz'y\\'hcrc '12; [he qmi: . v ' i \ ' :4 i“ 3.:1 am and ‘iindi in imgcr xi": Jr- 'm 1 .M [um um- :‘ustr‘iLtod In {M'- Emn-r u. M—i' ‘ W: ' n! l1LIh'IE‘:E.‘:xiH[l1C L‘:\7. "7 I r‘ v , '1~ 'L": :0 represent (Ev;- nri ‘ _}- lm .rlwy migmdtiti‘. mui ili.~.‘.[L‘-~. mm; I1“.|.:Lvi_h~.lr_c_~ wining Fl 1-:||.i\ .m- lln" .mclb u 7“ . ‘. v _ i": 1w. ruminalwztt M r;‘.'L:H.L1!'HL'q§ fulul~ ,I‘II)11_._‘{'|v.-‘.l|.\..‘]\ ‘-.-- J Mi {a in“ ‘ N; v _ m11p.;r1ic:f PT‘.‘ ~'.}h..llil'x-“ n.|u.1l.1l|;: -||l I‘v. “xiii. [. : 1‘ .‘ :‘j‘w ' jrw‘fi'fl‘ F1',x1'.- :.‘I§I'.Ili‘.‘l\1|:‘.__i|.3l[1|"‘\'I-|l-‘ i 'r ‘ ‘I- 7.3,- \. ——~H\- ‘ \. .— \ ‘I‘

.4‘ (H,‘- ‘

\u \_ _ ., q R A C. " \ .\ ~ x '.4\A‘ . \ x

‘ ..\ x\ \ ' '- y _

\ \ “x\—-—.

-_ 1“

N \\‘ \

\ VC. b4

77" T} Fig. 2:[\‘J SCHEMATHZSCHEMATIC SKETCHESSKETCHES OEO.F PRlNCI';PRINCI = ‘ PALPAL FOLDFOLD TYPES DIEEEPENTIATEDWFFERENTIATED i :NINTHE THE M'VVATATEMWATATE ARAREAEA ;'\.l\~.‘1:.-.tc Quarlrrmglc _

light quorz-feldspar cwss

'L rll .," . . ~ Fig.3:Fig.8: SKETCH OF EXPOSUREUREAT AT MlNDlMIND1/ / GG1—MINE: F1 synclmalinal foldfold refoldedrefolded I by F2

1i was [on high to allow shearing ”flow folds“ and ptygnmtli foldsfolds:irc are‘levclcspcrl. developed. To wliirli cxrcn! Fivf'olils of larger dirixensimis tlmn some (cm of mutrcs wrurelvngtli In nlmcrvcd at Mgamu Ridge mayr exix‘t, ix .1: present difficult [u alchilax The: .(‘S'nUHIP rinn is. liowevcr. .tlmi such- .. .folds , - are generally- of. small to medium (llI‘ilL‘Eiblt,.I115, TheTheVVltlL’, wide, DPCII, symmetric 0r .isymrnclrir‘ FJ—l-ulds‘ however. lmvc lwcii ”1:1;c ringing from several Lens ml metres to several kilmucrrcskbukes‘.‘.'itV‘3lL’l‘.g(l1. wavelength.Tl'ntj; Theyplunge plungeLL. to tlic nortli, generally with about 101;. (frosvlijlrlx at approximutcly right .inglcs tn FI-folds umuroccurm in Llicthe nurtlwrnnorthernMp Mga- mu. Riulgu. They are: wide, upen UndUldllOUS plunging Mat 50740;JMo0 nmtlxnoahml ofCARL uat,ii» acco-m HlprlHiL‘Ll by minor Crenulaliuns of 8" These [ranv-rxc (Un'lprCSsiHnJlcompreasiodlCdUlfL featuresﬁa an“ are

L'OﬂSll‘YCd to have rcsulled from a local restraint ml the clonglitionelongation1Iumllcl padellilr B1.The The

(9.112011 l'lf this Y'lf$‘.[\'.\-\H(. llCI‘HC‘ICY, LA‘JHUI b8 \lk‘l‘iik‘xl Al PC'ZsCHQ. W. Pohl& G. Niedermayr

5.2_‘ FaultsI Imlx I and.IIIIII lineamentsIIIIL’.I=III_III~ One fault only appears on the geological map of the Mwatate quadrangle, cutting m&bles in the northern Mgama Ridge. Minor fractures of dimensions which cannot be represented at 1:50.000 scale are numerous, hqwever. Comparison with the Taita Hills, where outcrops are more continuous, does not suggest the existance of many bults of herextent and displacement in the area SimiIarly, the impressive linear features of the Mwatate river dey,and the west- dope of Mgama Ridge, are most probably not foults, but zones of pronounced fracturing, jointing and cataclasis with little if any displacement. The Mwatate Lineament extends northwvds into the Taita Hills, and southwards into the Kinjaro quadrangle, with an overall length of around 50 km. 5.3 Mtonga-Kore Chmockite Complex Few structural data can be collecred at the exposures of thia complex, and these hardly allow a rational interpretation of the internal struceuee of the complex. It may be assumed from these data, that the complex lwbccn dfecradjy. F1-I I tf IIFa-folding;I III'.‘ g the former is represented‘II’IIII,‘ byII'.' a:IIII'IIIIII,I, constructed‘ axis (8)f dipping. 'I, 03I to 160IIIII ,while.Is.“II F1I is thought to be responsibleI ; I I for the'III strongheationI imprinted on the chnockitesII‘II'IIIIIIV. plun-2‘-I “I ging,II, 10'' III toLII theI north.'II F2-foldsI ‘ mayII well be present, but unnot be recognised beuu- se of' theI absenceII ofII! migmatitic,I' ' mobilisates.I I The complsx doeqnot seem to beI struc-III turally'L'EI', different‘I'Irz'III' from’III:IIIII its country rocks,II although k is considere% probable, that'III itI re-I presents. I a tectonicdyII I III III\‘I emplaced’ basementI IIIIII to the Kutw Group.

5.4’I I TectonicEIIII-IIII significance.IgIIIEIIauLI, ofIII theIIII uIaampfta:'lII‘IIIHIiIIIL‘II The Manpi thrust system

SmallII bodiesI I ofI ultramdcII IIIII rocksII I. haveII IL beenII exposed by prospecting pits at Mikeli,‘I' Mindi,‘I‘IJIIIII andII I west of‘ Kambanga.In II‘ III This distribvtion is here tentatively interpreted to re-I flectIIIIIII»II intrusion or obduction- II I alongI a thrust system, which may have been formed con-. temporaneouslyIIII,III III with‘ II Fldeformation.I ‘ILII The thrum would have been foldedI by“I laterI tectonicIII' I phases.IIIIIIII Supposedly,I uIII\ theIII thrustslyI I I, underneath’I‘I‘I“ I II theIII ~to~-~or~~hnrnockite~om~lex,III II RI I II II I I andII to the west atI the' . approximateII, I lower.‘ II boundaryI II II. ofI‘ the’II Mgama-Mindi'1' I " II Formation.I I II AboutX . 20, kms alongIII II strikeIII:I toI the"II southeastI III of"III MindiII occurIII' I theI importantII ultramaficsI ofI Man&,‘,‘I I whichI I urryI I minerahationIIIIIIm II I II ofI redI corundumII andI rubyIII (POHLI‘I .I. I & NIEDER- MAYR, 1977). InI view. of theII economicI I'I‘ I significance of these deposits,I I the‘II thrustI system will be called here, ,Mangari“-I’I VIII thrustIII system".I‘

5.5'1, -‘. Minor\IIIIIIII structures«tuning» BoudinageI'IIIIIIIIII.::IILI isI) commonI I throughoutII I Ig’II .I the area. Thin bands ofI’I more competentI I.‘L'7l‘HI rocksI (amphibolite'I‘ I IILI. inIII. biotiteI'IIIIII’I- gneiss,III» II» quartz-feldspar“III'" gneiss, granitoid gneiss,. andI: marbleIII II_I inII graphite gneiss mdII schist,IIII' ulcsilicateI I bands in graphite schist,‘ etc.) form5 I ellipsoid raftsI.." in.theirI IIII: incompetent’II. I IIIIIIII‘IIIIII'I'I‘I country rocks.I , TheI I spaces‘III betweenI‘IJIII'Ia‘LTI adjacentIcII III bodiesI‘III. mayII . beI filledI‘ll by pegmatoid_: ' I, mobiiateII (see chapter 7). or theI. countryIIt'III rockII‘~ surrounds them completely.’I‘..'. Frequently,[I I the boudinsI' II: are internallyI I foldedII. andIIIII rotatedI I in relationI 1 to theirII \ countryI IFI‘, rocks,I which isI considered due‘II to shearingI".I parallelI II. toI layeringI I , in,. the countryIIIIVII rocks. TheI calcsilicateII boudinsIIIIII in graphiteIII schist,I associatedI II with the depo- sitsI' ofII greenIll I grossularite,’ II I‘ have rarelyI beenI ‘III found to haveI a welldefinedII II ‘ longitudin$ axis. At MindifGGl-mine, however, such axes have been measured to dip with 40 M watate Quadrangle EU

1') 0400, approximately parallel to the above mentioned Ll‘Oss—‘t‘oltls. in addition to pie-existing layers in the rocks. boudinage affected also veins. and Veinlets oi the peg matoid mobilisates. Therefore it is conternporaneous with the [—‘3deformation. and parart’i‘ystalline. Late-crystalline deformation is indicated by bent twin lamellae in leldspar and in caltite in many specimen throughout the arem l’ostscrystalline Cutaclasis has aiilietted roclxs throughout the area. resulting in high ly cracked feldspars and garnets. which in some specimen are set in a finely crushed. matrix.

6. Metamorphism The metamorphic rocks of the Mwatate area are the product or» hithrgrade reeio rial metamorphism. Most mineral associations tound indicate aruplriboliie tacies. as already noted by ]. WALSH (1955:]7). During the present survey. the occurrence of granulite facies rocks was recogni7ed, and more details were added to the under standing of the metamorphic history of the area.

6.1 ProuressiveD Metamor hism The MtongaAKore Charnockite Complex exhibits clearly a higher metamorphit grade than the enveloping gueisses of the Kuras‘e Group. While in the former (”tint and clinopyroxene together with orthoclase. plagioclase, hornblende and quartz co artist. greenish hornblende with plagioclase characterizes arnphibolites contained in the latter. This observation of a metamorphic hiatus clearly supports the proposed cover/basement relationship between both units. Amphibolite facies mineral assemblages are widely developed in metavsediments and metaA/oleanics of the Kurase Group. Metaipeiites are characterized by hy'arrite and/or sillirnanite. the latter sometimes replacing the former. biotite and orthoclase. which may partly have originated by the reaction 7 muscovite + quartz + plagioclase ,, orthoclase + sillimanite + more. calcic plagio Clas‘e + HEOQMIYASHIRO1973226) except in the absence ofquartz. ()rthoclase is frequently corroded and replaced by inicrocline. Partial melting ot the rocks is ubiquitous. Metaibasites of the cover consist of hornblende. plagioclase and variable but smal ler amounts of elinopyroxene. biotite. and garnet, The amphil‘roliies at Mgama Ridge contain hornblende with brown or olive brown colours in 7., while those south and north of the Mtonga Kore Charnockite Complex are green. It is not clear. whether this oi‘rservarion reflects a different metamorphic grade or an originally (lifterent bulk co mposition. Meta—calcareous rocks in the area are composed olicalcite. dolomite. quartz. diop side. tremolite. rarely 7oisite and grossularite. The absence otwoll.mt<:nite in the pre- sence of grossularite suggests. that the lrighternperature stability limits oi the latter mineral [MIASHIRO 1073:275} were not reached. Meta-psammites and metamorphic. originally telsic igneous rocks consist mainly of microcline and quartz. with variable amounts oi plagioclase. orthoclase. mustovi te. biotite. garnet and sillirnanite. Flattening of q uartz grains at some exposures lead: to granulitic textures: the mineral assemblages. however remain within the amp ri bolite Facies type. MUscovite is replaced by orihoclase except in quarry-free schists :ri 30 W. Pohl 81 G. Niedermayr

Mgama Ridge. Orthoclase in turn is corroded or replaced by microcline. Partial melting is highly variable from an almost total mobilisation (granitoid gneiss) to the absence of observable mobilisates at outcrop scale (quartz-feldspar gneiss derived from ? rhyolites). The observations cited allow the following conclusions: Progressive metamorphism of the kyanite 7 almandine 7 muscovite subfacies was followed by a phase of still higher temperature, of the sillimanite 7 almandine 7 orthoclase subfacies of the amphibolite facies, as described by WINKLER (1964). Accordingly, extreme conditions of the amphibolite facies have been reached. The coexistence of kyanite, sillimanite and quartz, widespread partial melting and the ab— sence of staurolithe and cordierite prove that relatively high pressures have been rea— ched at a high temperature level. Metamorphism was of the Barrow-type, or the ,,me— dium pressure type“ as defined by MIYASHIRO (1973:74). Granulite facies rocks form the Mtonga—Kore Charnockite Complex. The main mass consists of oligoclase, orthoclase/microcline, brownish—green hornblende, diopside, hypersthene and some quartz. Minor bands at Mtonga vary towards more felsic or more basic composition. The uniformity of the Complex as well as the nearly total absence of anatectic mobilisates are a striking feature. It is conceivable, that the comp— lex may represent a dry intermediate intrusion into the Kurase Group, which becaU» se of impermeability to access of H20 during metamorphism recrystallized into a granulite facies mineral assemblage. This is considered to be one way of granulite-forma— tion by WINKLER (1964). More probable, however. appears to us granulitisation after expulsion of water from the rock mass during one or more earlier metamorphic phases. However, only radiometric agedeterminations on specific minerals within the complex and in the cover rocks will allow a definite statement on this subject. The conspicuous metamorphic disconformity between the charnocltites and their country rocks does not favor a relationship proposed by BAGNALL (1964) in the neighbouring N. E. Tanzania: There, BAGNALL (loc. (cit) proposed the formation of both metamorphic zones by one process. Diffusion from the granulite facies rocks of K, Si, Al and 0 would have caused a migmatite front in the overlying amphibolite facies rocks. Typical mineral assemblages observed in thin section and reactions considered in» dicative for the conditions of progressive metamorphism in the area are shown in fig. 4. The relatively wide range from 3 to 7 Kbar and 600—7000C illustrates the comple— xity of the metamorphic history of the rocks in the area.

6 .2 Retrogressive Metamorphism All metamorphic rocks of the area exhibit features of partial adaption to lower p/t conditiOns following the peak of progressive metamorphism. We include here tentatively the formation of 7 microcline at the expense oforthoclase 7 hornblende at the expense ofdiopside 7 the kelyphitic shell around grossularites 7 muscovite in granitoid gneiss and graphite schists of Mgama Ridge in rocks of the Kurase Group, and 7 hornblende and biotite at the expense of pyroxene in the charnockites. i\'l\‘.'tlid[13(QLlJtllilJlC

().3(:01TClL1[lOHUl‘UIL‘UIIIIOI‘plllCand structural liismry Unfortunately, the application of radiometric dating rnctlzotis during tln- prawn! survey was not possible. Act‘ordingly. the following correlation is imscd on geologirtrl reasoning only. and has to be understood as a pl'CllHllILlT'y .r}i}'.~rougli.

[\Atonga-Rorc Kurasc Group (ilinrnockite Complex mtaclusis rctrogrcssivc reactions FJ-dclormation (more thermal ampliilmlitc fzrcics. pcnctrative pegmatitcs)

gzrunulitisation .7 Fg—deformation ampliilmlitc limics {low pHZO) IHUTQUTIUI‘PliiSIn‘ unatsxin and migmutimtion {iiigli pHZO‘; F1 deformation (Manguri tlirnst system; cnplacemem m“ ultmmafiim: lower grdrlc V'ir‘trnnor- pliism ?) Sedimentation denudation uplift presently unknown structural and

metamorphic events

bar) (K

Fig A CONDITIONS 0? tAETAtAOFPPHISM N THE M‘NATATE OUADPANGLE Pflud DEDUCED FROM MINERAL ASSEM = BLAGES AND lND'CATlVE REACT - DS- ONS (SHADED AQEA) Reaction curves and phase boundaries of

Al? 5'05 m ”2‘s“, 1”.“ wNmER 402m Pressure

1 alblte.p0taS$Ium feldsparoquartz 4 H 20 - men tremolitemalcue.quartzdalc‘dolomule

Wk) dropsdeviremollte~calcne~quartz

rt muscowte . quartz‘ poressaum fold - Spare Sillimamte \V. l’1'1l1l1\' (i. Nitxlt‘rinayr

7..\liner111Deposits .1ntl ()c1‘111'1'ent'e5‘

7.l (ienerul llntil 11tLite 11‘1‘1‘11tl11'. 1111 ”1111111111 tle11115i15‘ 111 econoinit‘ signifiednt‘e were. lx'nmvn i:1 1e.\‘11.\'11t.1te .5l1eet 1111-11. 'l he l:' 1001') 11>l1111i1'11l111111 J \VALSHJ‘JSS‘,111.1te25tl111w 111‘11111‘e111‘es1.11‘l5.)xtnite1tntl 5illi111.111ite. 1111.1 the 11.1 111111111_yingte.\t1le511'il1e5l111.1li 111-15 with ele\'.1tetl 111111e11t511l 1111111111111 garnet .1111l11l1n11111l1i1'0) 11111l11111111l1e111l ('11 51.1lli11e li111e5111111‘1 Analysis. Since then. the 1li51'ovcry 0f geniqunlity green q105$til111it1 .11 \le.1.111:1.1rttl11i l\ll111lll1&51.‘l111111;t’1l the. 21111.1 into one Ulil’llti important 111‘1115111111-111‘111 l111.‘er5 \\'itl1.i11 ll.15t \l‘1'1111. 311.11111in1g 11‘ the .1111 within the Kenvn Austria Miner.1l Exploration l’rojett. «l11511i heel in this report. 51:1'11e1l t11 investigatetthe geological controls of the gemstone tpt) sits; in 111‘ ler t11 .155i5t 111'0511111'1111'5 11nd miners in their t;1sl\‘. ln addition jeverdl new mineml 1>et111":1e1111.511t red 1.11111-1. 1111‘111111i5‘e. l1lue zoi5ite (t1111711nite).11reen tournmlr ne. IL‘tl 1‘11r11111l111n .1ttl‘3:. lxyanite. tildgllctltc. 511incl 11111lrutile coul tl l11 found or re- til?l.llcll. ‘l‘he (IlDA 1'1e1'i11l survey 1977 Covered the Mwata'te sheetttnally, l1otl1 with 11 radio metrit .1111l11 111114111111 511111111.1l11ntgllightlines .5‘111-1cecl 1'11 1 l'xlll tlistanee.ll1e1n111111e1i1‘ contourrrnap 11101l11111ll1ytl1e 5tuveyi5 geologitttllyinter'pletetl111 the. following ‘l111111 tt'i 1'.3.\1.'liile1'e1‘11111'l;5 (1.11. tl1e1;11li11111et1‘ie resultsmaylw l‘11tt111l under 7.7. An etononi .111111‘11i511l 1n the area. is (ontlllnﬁ‘tl in ABSTROMINERAIQS report “Geologienl l’1'1157111‘1'ti11g anti lieonomie A551‘551nent of the Gemstone Belti115011tl1e.1 stern lieriya". 'l‘he 1111111015 vie-W5~ expressed in tl1e1Collowin11 pages does not necessnri» ly relleet Ali.“ l{()1\1llNER.r‘.l.'s opinion.

7.: ,l.ll[C[pI't.’lJtl()ll of. the Aeroniugnetit‘ Data (fig. 12) A regional treml of the magnetic field in the area is indicated by the following ol15erv.1ti1'1n5: \1.1ltit-5‘ are 1e11e1'11ll\ l1elmx 54 100 gammzts in the SW. 11ml .1l11'1ve the m1'11l\.i11tl1eNE. Single iot'k l111111l5 are ee1t11i11lx not tr11t'e11l1le on the map the stint» t1111'1l grain however. i5 wellr epresentecl l1\ the predominant li1e etion olisolinexilong 5t1‘ilx'e. li)’ visual i11tei11retitti011 l11111‘tl011111in5‘ 1111111 he tlillercntiated within the quad» rangle: the 5<)t1tl111;1.5t. the M55111“ Ridge area. the Mwntzttc tintiforni with the. nortlr e115'1..1111l the 5in1g11l111'liet1ture1>lthe Mtonga 11111111111lv in the center. the 5111.1tl1e11st..1regular111tte1'nnlhighmintll1.1\1.'51.5.':1111111g1e1.l1111'11.1llel to the 111-3. 51.1111511l 1e1;i111111l Sli NW 5trike wt the [OL‘liS.l11Llll§ .11e11.tl1iel\ 5oil l1l.1nlr\tt5 (over t11t.1l1 ly the1111.51.1llihe1‘11t‘l15.;1111l the5i11‘11itiie11111'e11l the (lilil‘Q‘I'CHt l‘lCld v11l111'5 1.1111101 l‘e .151 1.61'111i11e1l. 'l‘he 111 geneti. 111rtter11<1ve1 the M1111n11lxi1l1e 2111.11 Sl1(1\.\.5‘ well the geneixtl11(11'tl111111 tl1\1.'e5,terl:.' ttcntl f1lfllt‘t‘t)(l\'$.lllc l1i1_1l1:5.1111ll11\1.5tire 11111 1111ril1ut11l1le 111 511eg1iii1‘ 1111 l. units 111.11111e1l in the .11'111'1. ’l ht- 1N’lw1'1t11te untiltirm is well t111111'11l1le l1y the '111'r111111e111ent ol the 1111111netic 111111 t'1i11'11' lint-5. 'l‘lie .111111l1il11'1lite5 111111111e1'l .11 the hills. ;\;11)11i. MLt':11gCtCt1i;1111l11tZongolu 4 ...... 1 . 1 1 1 1.; 1111“,” 1'11 ‘11" re111e51-11t1'1l 11.11 ll11t lt1WS. lne«l15t‘or1't'1nt‘e netween .\'l\\'11t.1te l'oii‘.11':~ 1111l MeunH-Mintli Fortuntimn 5t1ggeC5tCkl l1y the 1>tite11111 1111tter11 111111l11111rtl11.\e5t or .1\lt111111.1 i5 5i111il.‘11l\1'1'ellet'te1l111th1e ptttern 11ltl1e1n11g1101ie' contours. ln the 11111‘tl1 1:11.51. (it the 1111111 1111121. tlte 51111110511l l) l1\\11li1)11litl1e rOtl15‘11n'l putly l0l111te1‘ocl< l111- 11111l.1z'ie5 i11 eonrituntiun with ;1111111 11t little v.1riul1ility 11. 1'01.‘ l1 51151'1111til1ilitie511111111— 1111‘.1 111.111'1111‘ 11l211‘1111tte1'n. (.1111L1'1111'Sti11e1 (ht .1\l ugenn l'111'11111ti11n .11‘1‘1111‘1‘1' ﬂat 1111.1 ; - 11 11:11. 111111:1.11.11'11ll1'1tti1tl16‘11'111‘115I1‘115'L‘. Mwatate Quadrangle 33

The positive Mtonga anomaly is elongated in a north/south dwection: highest va— lucs measured were 34625 gammas. the lowest 33910 gammas. To 1110 north. a gza dual decrease oi the values takes place. while the an» em and western ﬂaa‘afe qui» LC steep, the western one slightly more so. To the south, the anon’lalous values decrease abruptly north of Kore Hill. The positive pealr ol‘the anomaly liesjust southwest of Mtonga Hill. To the Southwest of Kore Hill. itself reﬂected by nearly background values, an impressive negative anomaly occurs, This is elongated in a direction which seems to cross the regional strike in that area. It is difficult to evade the conclusion. that an intimate relationsship exists between the Mtonga Kore Charnockite Complex and this unique magnetic feature. However, the shape and the configuration of the anomaly are not in accordance with shape and internal structure of the (Tharnoclrite Complex. The source of the anomaly is different of the rocks which can be observed at the surface. As to its nature, only speculations are possible at the present stage. Most probably, a considerable concentration of magnetite will be the reason for the high values.

7.3 Green Vanadium Grossularite Green vanadium garnets were first located in 1971 at Mindi and MiI eli Hills. Little later, the Mgama Ridge deposits were found, and actual production of the gemstone commenced in 1973. It has since attained the following values: Value in 1973 1974 1975 1976 1977 Ksh 640.794 1.616.818 831.774 1.391.902 1391.948 The ﬁgures were supplied by the Mines Department, Nairobi. The important new find of gemstones in Kenya soon aroused the interest of germ» mologists, and results of several very involved mineralogical examinations were published within a few years (SWITZER 1974, GURELIN 13’ WElBEL1975 SCHMETZER et al. 1975). From these publications, the mineralogical Characteristics of the green garnets may be summarized as follows:

7.3.1 The mineralogical characteristics The green garnets are grossularites, which theoretically have the formula 3 CaO . A1203 . 3 SiOz. The chemical composition of a well-coloured stone from Lualenyi-Mine/Pit No. 1 was found to be (GUBELIN 8t WEIBEL 1975): CaO 35,1 % (37.3%) N320 0.1 57/72 MgO 0,5 % MnO 0.75% FeO 0.05% Al203 20,9 % (22.6%) \7203 3,3 % CI‘203 0.190%) Ti02 0,25% SiOz 38,7 % (40.1%) Note: values in brackets are theoretical contents of chemically pure grossularite Internally, the vanadium grossularite contains liquid inclusions and minute cry~ stals of different composition; among others, quartz, calcite, and tremolite [”byssoli te“) have been made probable. Externally) idiomorphic crystals or irregular nodules 3.1 \V. 1’1;lild'\’ ('1. Niederinai'r

”potatoes", 1.11 these garnets are surrounded 11v .1 kelyphitie s11L'll.L11ns1st1nL'1»1 L311 11111L-. L'linopyroxene. spinel. quartz 111111sL'.1p<1111L'..

7.1.1Ilu-geological Controls ()1 the utologit: .11 L'ont'rols Governing the tlistrilhution (>1 tl1egreeng11net deposits vL-rv littlL' 1111s11L'L'n published e11rl1L'r. It 111111 been 1L‘Lou111/L‘11. hov1ever. that the Vana— 11111111 11s the main colouring agent was most niohahly derivedf r0111 originally bitumi- nuus substanees 111 the country roeks tGUlSEIlN 5V WEIIHLI. 1975}. During high 111117 1lL' 11101.1111111'111115111. the lviturnen was transiornied to graphite. while the traceanetals were IIIUl‘il17L’Ll and could enter minerals then heinL7 lorrned. The basic lithological L'nnirols 11111r'lvlL- hands in graphite gnciss 7 11.111 heen estahlisherl before SKIDGES 1974‘. During this survey. all producing green garnet mines 111‘ the quadrangle were visi- ted and essential geological Features were mapped in detail (digs. 5 7IO}.

Minkent'o-rnine (fig. 5) The mine lies on the wcst7slopc ofMtzarna ridge. A 111ghly varial Ie series of musto— vite7graphitesillirnanire sL'hists and gneisses with quartz and pcgmatoid lenses and 1117 tertalated (1 11.1117 1L ltls'p'ar and granitoidg('nL'iss hand .s 101111 the higher slope 01 the rid7 gt around the 111111e.IhL' l’OCl'tS dip quite unilornily 40/090 In the Opencut a band of 1:121}rhite schist with layers of yellowish weathered. originally pegmatoid boudins has beL 11 found to contain green garnets 11101151 115 tootwall T he productive horizon is the lower one of the. 1101111111 layers; lure the houclins are less 111111140 em thiLk and 70 cm lonL thev lo not have defined lone axes hut are more or less round viewed vertical- 1v to the toli'rtion. They consist of nontronite and some lirnonite: green vanadium grossularite is luinu found in 1'1111 ofsinglf houd ins or 111 the spam between adjoining ones. There. quart/ oeLurs' together with 111L511L11tes grossularite. trcrnolitc The L'nLlnsinLr gray1111111 s1his1 L'ontains several per'L'Lnt 111 su lfidees 1‘ 111111111} psrite. specimen 1> 1111,11,; 'I'hL' exposures 11 Gitshureanint‘. situated about-" 11111southotMinkcneo-rnine.are 11L1'111)'i L"nti'L 11 to thL ones 111st dwerilnd. ALLlinuly. they are not illustrated here.

1.11alL'nyi 111111L' no.1 (11g. (1) 1111s mint-- is situated 1111 the steep western slope 01' Ride hill. Here. the roL'lss mapped 111 the surroundings are graphite—sillimanitean11st'ovite sL‘hists and grieisses. with hands (1111;1'1111110111 11nd quart/feldspar grieiss. as well as several interralations 1'11 L‘ry7 st rlline limestone. (1L'11L'rlll v. these rocks 11111 eastwards with ~10 500 In the 011111111 t verv e11111plie11ted relations have 11L111 111111111TliLi"Lr111rl<.'1lle wall forming the 11L111'71L-1'111'11l 1'.1st7sl11pL of the rut is a pegrnatite vein L'utting across all other rot'lts: it is 1111111L'1L'11 11); 11 strongly weathered 1‘1llIll—l‘I'CI’Ci’d to the east. which then. 115.1111» 1:111. 1111110d graphite s'L'hist with 111terL1111'1tions ()1. quart/1L Itls'par gneiss .11111 :11111'111L'. heavily 111'1111'1111'11 1my .1.\1111 plane told: 11111'11ve7le11t'111s r1111 1Lw 111Ltres.

\Vt'st (>1 the |i11utl 11111119peginatite,1111.111tielinalstruL'turL' L'.11111L'1L'Lognizetl11}; t1 O attitude 1'11” 1\v11 LillilIl/d‘clkﬁl par’granitoid Lineiss hands which is then 101111l 11y 11 sxntline 101'111L'l1 hv gr 1phirL- sr'hists w ith qu.1rt'/7\'L1111L'ts 11111 lw-mrirL 7g11phit’L lenses. '1 .1Ls1 .sLllisfs111L: 11111.11sLlyl1'11111'11..1sillusn.11edm 111;. 5. Iiiese rrlrservatimrs are inurinetetf to rellL'L't 1=1 geological 111s1111'v 1;? 1:1

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folding linliin; 4' ncgnm‘vitc iiill'HSiUIL nnil .: in l."ill‘i,i“.£j ’lm viriiiunﬁ The W” . ' '. ,,1i.1: “i“.i . i. i «,1 1l\1‘)r“. ‘ivtxumri .Hv lint vi. L, ‘ n x. ml inpi'tn litizigwii «, iiuxt 1110: ['5‘ ,5 in 1.1m llll arm; 1,. As reported hi“ the mine niinmuw. green vunmmini giflw‘ijlyiflit‘ with LIH;:I'I.’. ,w znolitc. 7L)l\l‘IC. utg, Wax lUlIIltl in L1 “rm-l W'IHHH soil graphite w lHSTS [llUllfJ‘ the pct, l‘fli‘illtL‘ wall ziinl untiniiing scvcml itieti’vs lNJlW'x‘.’ thc pry-writ pitilmn'. wliurc ii Mix: lt)‘s[ .1! the liotluln at :1 small shalt. Amnnil the. DOS? ol tlli’,‘ .uitin,linu lim‘nictl lijy ihw Litiiirt'xrl‘cldxpin' aiss. a lcSS itrmlticiivc lnungh «>2» tlic I'CL‘l wan liillMVi-‘il l()1 .wx'cml niviw‘cs. At prom-m”. lmwcvcr. ”Hill-C51]: ‘HCL LiUl lw such. in this minc. ‘hc inwdiitiim. int-in; stnppcil

Lnulcnyi minc no. 3 (fig. 7) Sitnatcd in the upper reaches ml. d small Villlﬁ‘)‘ running limm noilli irli Ride hill Iv, [hag ZilJI'ElEi‘JS'C‘ this mint- ecntls ovur .i (unsitlc‘mhlc l'lDI'i/Oll‘éil and mrtiml \lifwtall LC. ()nc pmtlnt'iive hin‘iwm exists hcrc. hill :1 Considmuililc piii‘t ol‘ the nutlnvtiun wax reportedly {013ml in nent—siirlzicc hluish Claycy pods. clearly a product xvii weathering. Tho prinn’n'y limriyon 5061715 to hc quite puor, and has hinlly heen lini. )W‘L‘kl to mmr than a low lilC’El‘L‘N‘ ilt-pth. It is :1 hand of small bonding ziin. {mind if! a (ltirlx' I‘CV. sandy graphite st‘liist. which in its turn is' intorcalaicd in a writ: Oi.TUUM‘OVllL‘7QI:ll‘lllv . . , . i [C \‘(liiﬁu wnii tin.1it/»5tiingciz< anti pcgnintml lcnscC‘ .li ti occasiz’mnl hands (1i‘L1llJTT,/* A , . . . .y ,. ‘J I feldspar .iml granitmd gnciss. All thaw t'()Lil(.\ (lip wnh zilannt ill] in im' Ctibi or north-

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Lualcn Y i mine no. 2 lli\ 81 ,télJ LUCiill‘d nnly about 1 kn) nmili ml ‘l.iii1l£_‘11v\’l mine nu. it this 0a (in lies mm! pr’ulwgil'xl} in the same lithosti(itiigxxipliiu horizon as mines nu). l 21ml 3. The . '21 cx’pix» «cs nn‘x‘i rmitc—gtiiphitr suhists with qiiartV—stringcrx‘ :nnl pc-gmgitoiil hands. inn-real: ll with @111 ni/ lulglspiir :intl granimiil gnciax lmmlx~ the latter “milling intr'u pewnati ts.» r[‘ll\,‘.‘;c H)il'{> .‘i .p gcncmll} with ll) :W in the Cd\[:él.\i«}l}3lilf1L‘i‘ijlklﬁulﬂilll>2}llk"‘ up Lu (them If) HiULI'L‘S win/c length are <>l cz'vnhlc Folding: i5 tlisl‘iui'nionit, the ingwn- potent gmp' itc \Lliists liming mart- intone-sly ilcl‘m‘mcnl than 1h:- (Ompctcnt lolgii wiv isxcs. ln tln: wntion unveyml. loin lmii/uns contriining given g t ‘ have l'wccn it" cogni; 'i. .iltnun li lmii/mi JILL l min the nun: i'i'i)kl1‘il'll\/L‘ nnc. In thy north, [lit‘xc limi/unx HH'l'c iniz; onc. in the \OiEll‘i. ihm.‘ {CG-RC [u he pi'mliiri,ivc_ 'l'ht \'ATL1(ll‘LllIl gruwnlnx’ite ix lmiml in pm‘lwts mi ltnscx within the ixmtlnrtiw lim‘iwmx whith an: , ‘ I1 _' l 't ': , pztmgm \l' :isxntmfcu whh 1 iilxtijh d‘ l: ilw.’ gil‘iwc for Minlcwiiu) mine. The {lisrii lintionrul Hull pHClil‘tSlSll'Il‘U‘llltH‘ l3(‘7‘,‘.:‘\'i31..ll'llO‘. [it nil- in lin hurl \ (:vi‘

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e tlilltiztnr1' ‘ 'i.‘-."vi'l\l§1:;*-(>i- ‘ :ht ~.(;3" “ - *x e r . tater;_ 1 in. the l'.;lit’1; i pair ol the V . . . . y r [ll-Lil‘s .'7:li\|_\"»‘\'1‘.t‘q".iiillift‘ ‘ClllEl’Q. O fie} THJlI‘l‘iC lit'tl l'l . . 1, , . :77 C ,l . ll 5 UJ'tVCI' ILH'C. ll’liu > ()3 tlIL‘QLJldI [Wild .ln :‘ rte been hunted by » , > . ,. . . . . 1 . stematu prospettniu. lhese tontain tiny red r orunnum t’ivsrals see eelou ,7 ‘ .‘- ‘ The (KB-mine r" l’yworldn‘gs provided the occasion to map the distribution oliuieeil vanadium garnet nodules on a partially esposed plane ml the productive hori‘lon, as pointed out by [lICHllHL‘AlHIiI‘lagCI'.l1)t)UI‘()}‘/lnii)‘tl.IllC‘tL’l\11(V[CCI()Iilt'tt)1111‘t)lt)lillt‘ll' location. The nodules seem to occur irregularly and unpredietably. wherever the ori pinal rock may have had a suitable eomposiiion. The seetion oli lie. 9 shows. that the tjl‘tfcllgl'i).\‘.\lllrl1'ii\_‘lHﬂ'LZUI‘i here is at the base oli a marble bed in ‘IliLf uppermost part 01‘ rtrustoviteeraphite schists. This is notably different from previously described mines.

(iGlAmine f Mindi Hill south flirt. TO: The excavations of this mine he westwards ol the rounded summit «it a small hill south oiMindi Hill. The summit is formed by a thither marble-bed. whith is underlain by graphiteanuscovite st‘liisrs with an occasional interealation oigraphitc-sillimanite gneiss and lenses or irregular bodies of ultramaliic l'()Cl(S. The Eraphite-muscnvite schists in turn are underlain towards the western base oi the hill by liiotiteigarnet ‘LV‘DQTLL. General dip is with 30:: to 4U“ to the northeast. Two larger trenches have been opened to a depth of about 8 metres below the surface. both with short detlines as depicted in fig. 10. Green grossularite was produced from one horizon in both cuts: the geological situation suggests. that the two exposures represent the limbs ofan F1 Told {an antiliorm with a northerly plunge). The produttive horizon in both cuts is exposed on the western ﬂank ofthe worv kings. so that the distribution of accumulations of green grossularite as marked by the mine-manager could be observed. Again. their lotation was found to be irregular. The green grossularite horizon at GGlimine consists of a bed of boudins. which viewed vertically to the hori'lon are mostly round: some have pronount‘ed long axes. whieh have been measured to plunge parallel with the dip of: the Folia‘tion. Summing up the results of detailed mapping. the {allowing geological controls \ u uld be established lior the presently known oreurrent’es and mines of green vanadium grossularite in the Mwatate quadrangle: , regional lithostratigraphy All presently known green garnet locations lie in the higher part ot the Lualenvi Member of the MgamarMintli Formation. This is not by ehanee. as understood at pre sent. but may be explained by the geot‘hemieal and lithoiogieal rharaeteristirs oi the rocks concerned. ~ lithology Green garnets are invariably found in graphite gneiss and schist. either in originally more calcareous beds or at the contact between such beds with the graphitie melts. In both cases. the availability of silica, alumina. and lime lot the formation oliurossur larite duringr metamorphism was given. availability of colouring trace-metals ageot‘hemistry‘, The above Cited analysis otia green grossularite lirom laialenyi shows the rolouring metals to be Vanadium i‘ \r" J. Manganese Mn: 5H} \‘x”. P011? 4‘\' (L Nicdvmmw‘

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1.11. Elm (31; i-iiiiiiL‘ .11'L‘ .il "'.1tcLl it; thL highL-i p.11'tottl11‘ tliiL’X lllllm I1\‘11L' L’iilniitc \1’l11:15,1111l‘-,'.11'L"‘.\ 111L‘t1’L's / ’1 5 1‘ marble l.“rl.‘\l. l 1 it's lowcr 'I.11't. l1: 11,: irr1'.:ul.1r b I llk.\ o., 11lt2.1n;.1li1 rmlxsl1.1\IL'bL'c11loL“1teLlliysv steinutit‘pi'I'iSpL-L‘Iiiig.TtL-L'ontaiutiixx'rtwl(11111711111111L‘IVStulsIsLx'liLloA‘ ' a l 1I j 11 The (Kifrniinu ,I" liiworlx‘ings provided the 111'1‘11sio11 to nip thL- 1list1i1iurion (>l‘pﬂljcll v.111;11li11111 garnet nodules on :1 partially cxpnscd plane 01 the productive l10ri7on,.1s pointed out by IhL- llllli€*lll.lll.1gCl. ln ouropiniun. tt is 111: turtoniL‘ L’ontrol oi their loLution. The no1l11lc5 scorn to mg 111' irregiilmlyanti l‘1liplreklllflrll‘xl:ﬁ.V\'llCIL‘\"CY:l1L‘Ul'l’ ginnl roLlL may have lILiLl .1 suitable composition. The stion <>l ll}? 9 showx th .11 the Ll'k'Cl] Irrossularitc hwy/on here is :1: thc b we of .1 marble bCIl in th c uppmriiost p111 oi musL’oVitc grapliitc sL‘hi ts. This is not 1 ll» different from previously LiL-sL‘ribL‘Ll mines.

(.Gl -niinc ,I' MinLli Hill south l‘iLI. l0 The excavations of this minL‘ lic \\.'€:I\‘Val‘il8 oi. the. rounded summit (ll. :1 snmll hill south of Mintli Hill. Thcsununii is lormecl by .1 thiLcr 1n;1rblcbc1l.whi1l1 is underlain by gmphiteimusL‘ovitc schists with 1111 occasional intercilation ol‘gmphitcisillimunite Lgnciss and lenses or irrciruln' bodies of lllffdﬂ‘ial‘lf lOClx'S. The grupliitcimuscovite sLhists in turn are 11111lL111111 tow1111 s tllc western base of tin hillli1 lIiotitc—gzu'nct iiL‘iss. (veneral (lip is with .10 to Ill) to the northeast. Two larger trenches have becn opened to .1 depth of about 8 metres below the surface. both with short declines 115 (lepictt‘Ll in fig. 10. Crccn grossulilrite was pro, duceLl from one horizon in both Luts: the geologiml situation suggests. that the two exposures represent the limbs 01.111 F1 *fOlLl (1m antitorm with 11 northcrl V plungcl. The productive horizon in both uts is c.\xposLLl on the \xL‘stein llanlL' ofthc workings, so that the distribution of accumul.1tions ol qrccn grossularitc 1s markcdl the mine-manager could he Observed. Again. their lr>L.1tion \\ is tournl to bc IIrLgulary. The green grossularitc horizon .11 GCrl-IllinC Lonsists of .1 bed oi boudins. whiLh ViCVVCLl vcrtiuilly to thc horizon are mostly routi

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giossuhiritc F 1111;11'tz 1’ \1'Qii1151t0nitc 1'111111.11'tiiit1'1.1Sxi1<1\\nin'MiYASHiRU19.1:2//1Ln 1111111 i1cipt111c:)<1i111ic 111111151whore.gi'oxsuiarite \7111111i1ii1111v1 i196 11 unst11i1ic 111 siightiy hi1 ghei 11111111311111t111115 01'11111111111111-111131111118111111111115111117111 111111111\1i\\1'11tzit1‘ 111'1111.H1,1\\'~ 1'1'1‘r oniy research 1111 1'1'1gi1'11111i .11.;1i11 111.1y 11ii11\\'1i1‘tii11it1‘ c11111'iusi11ns. whcthcr areas 1011 Mining 11.1111ii.1si1,111it11 >1i'111111i1i 111,1 1-.\1'i111i111i 1111111 11111511c1ti111; i111 grossuhu'itc. 7 tectonics Th1: 1i11i111'1n111i1111 11i'1h1: 1'111ri1's containing grvcn grossuhiritc hefm'c. 1iut'i11g.;1n1i 11i1 1111' 11111111111>1phi1111 is in 111111 opiniun not111ii1111't'1'1111t1‘0i Ancxccptiun 111:13'i1111'11511s. '1\'1i11r1 iimuimn ildnii1111n i11'111111i11 i11111 1ii1'11t 11111t111wi1h Ciuvcy 1111'ixsi1y eariy ii1111i1 tint; .«1'111'1 .1; 11111-11 ihil)";1 ‘111i.11.11i11'11}i 111i1111 1111. i. 111'11t (1(§.1-111i111:,Arworixings .1110tiii'11 siratmi 1111111. V1 iiczc ti'11 1ii.\'t rii11'1 ti111'1 11i 1111111111 1:111:3511i11it11 within the prti>1i111tivc horiyon 1011i1i i111 111:1pp1-1i 11111'0i111i1i1111'e \\ ith i ' 11ti11n 111' iohi axes 111.1-«i711111‘11i. The 1'1'111'1'1'11111‘1 111'1'111'1'111111' 111 141111-11 éi'iHNIJiAI'iLC within i1111is itmneri 111i ..i1111.11ii11,«‘" iicnti1'11h11 i101i' .i11 11,0<« :1111'1i111'1: i1r111i>l11 th1111'1111-1110n1:1,iiti11'111'31i11 11ii1i11'xx11 «1111211111 .14 W. 1’0111i\‘ (9. Nietie1111ay1

SAMPLE No. Ni (71) (fr \ (In Zn

P 1013 R 105. 15 70 275 198' 7250 P 1024 R 300 50 200 460 93 2100 P 1027 R 4175 103 70 85 55 3500 P 1050 R 33 8 25 80 30 78 P 1052 R 195 55 1,70 575 BE) 8750 P 10511R 53 5 33 10 13 185 P 106611 105 ~15 215 625 48 7500 P 1067 R 178 50 173 435 38 11750 P 1068 R 80 ~18 143 175 55 700 P 107‘) R 103 65 4.5 175 180 10250 P 1082 R 195 30 1418 1-100 63 403 P 108‘) R 90 75 63 700 15 16500 Note: A11 va1ues in ppm Table 5 7 Trace meta1 content ofsamp1es from 1V1gama Ridge (AAS assays after hot 1eaehing in HF/HC1 13y the Chemiea1 Laboratory. Mines and Geo1ogy Dept, Anav 1yst E. P, Mwaniki). P1013.1024.1027.1053,1066anc11079= gossanous ﬂoat P 1050 = sheared granitoid gneiss P 1054 = vuggy.1in1onitie quartz P 1067 = graphite gneiss with 1imonite P 1068 = limonite with quartz and graphite P 1082 = bluish grey e1ay t~i11ingjoints above the green garnet hori70n at Lualenyi Mine No. 3

SAMPLE No. Ni Co Cu Pb Zn V P 11041177 2973—5 7 7707 7703’ 100 405 85 1> 1128 R 1050 85 810 78- 975 1100 P 1133 R 420 155 85 650 30 2000 12 1138 R 2000 80 185 475 275 ni1 Note: A11 vaiues in ppm Tah1e 6 Trace meta1 content in gossanous ﬂoat from Zongoioni (P 1104131 and the Mindi area 1AAS assays after hot leaching in HF/11C111ythe Chemical Laboratory, Mines an11(;eo1ogica1Department.Nairobi Ana1yst: E. P. Mwaniki].

res: The data ant1 ohservations C011CCEC(1 so far do not support a tectonic origin. as 17111.5( (Ti/(116111 are rounded in .111 directions. AﬁkOI‘diH}; to the xensu strietu use of the term. however. houdins shouhl he dearly e1ongateri para11e1 to contemporeaneous 11'1111711xex. 1t appears. that these structures may he inherited trom the original sedi— 1nent>ﬂand may represent 1arge.mure ea1eareous coneretions. or possih1y he of (iit'é'Lt hiogenie derivation. Further research into this matter is suggested.

7.5.31’1'05peeting Prospecting for green grossuhirite deposits may involve the 1-()110wing methods: 1)iret:t 111011111115 : to examine r'othx‘. grave1. ea1erete. 5011 (11111 a1111vium for traees ()1 [green garnet lnLii1L'L‘t mytlnuls .» to SOLU'Ll‘. 1:-111<.‘1.1l.\ . 1l._’\iliL‘.1tL‘.~ .10..e1;:{1;1pl1'.01'11L'i.\.1111'l>gl1i ly. l11111'L:vL-1'.1)11c111 1111'11‘L' ol tl11'sL'x'i.-1;exz11;iyhL'11:11'.1il.1hlL'timc. rcwaL'x .111Ll prior iniiirnmtion. [)11LL'1 methnds mt L-ic'L‘n ,1.11‘11L't pi':1;.[tL>L'1i11g;11‘c .xi111plL‘.'l‘l1L,-y inL'l111lL~ visual inxc‘ tim‘.t\111l,1111l<1)1:11"11(11.\ .1ll111i11111.1.1l.v '. and .1111 hills l‘111 t1:1jy1'hiy~ Ul‘ 1hr: 111i11L-7 'al while traversing prospective 311-1.. Much more involved .11113 1i111c-L:<;11si1ming tli.‘ "icvlng 111" Mill. in mulm 11',- ;;L-'t‘;1r1tL* the grain \l/C \.\'l‘llLll must pushahly wontainb L:rcsn garnet Ll1ips from l.11z 'r 1‘17Cl'1 [1:1na and the ting Ll'List.(}L'1101.1lly the lranti r111 tuLLnl..-.111Ll.1111111LliziinLttL-rwillhe111031..Ll1'111t;11_rcr>11€.Sicving \lUHllil proleI .1hlc‘ he L'.1111L'Ll11'.1t in w: 'cr lor (.“(lPlL‘ in .1 7.00l .l1'.1111 L'Uf in l1.1ll .nLl tilled with wax-1;. .15 the L'olmir slit-11c tiny Lhipx will then he11101’L‘1L'.1Llil}',1‘ec0g111/L‘Ll, 5.111.171l for \Kk’l’tVlnu '1111 he L'nllL‘L‘tcLl {111111 the ixsc (11‘ the l111n1ic :soil layet ﬁniostly less tlia110 L'm in Lhc 111m or slightly LlCLL‘per 1llr<11n the. l1<>1t0111<1l-.1pit;15 loop .11. :1 shawl .\ l‘léiLlC 1. ll the 5170. of the .1111.11lL.. is 1111il111'1n giiLl pittinn and 1111111. 1111}; nlL:.1.1'11€1-L:l11p.\ pm smnplc 1:11.1y lt-z11l to r1111.» rsl rl1L‘1lir.1rih11" i011 Dl giccn grnsxw Pits .111Ll Erez11'l1L‘51nm'L-intelli lkllltv in the SOll‘ which Will lulll t” PL‘CC PYUH‘CKUILE gentlv. [he (lixtemcc of sampling could 1' l1>1'.1 PI'L‘llElIlHJI’V snivey {ahuin '21) 111 . . , . . 51111:11'c along the pmxpcctivc hori'xmig. .111L'l 111111'h 311..1llc1 LLimx 11 11) 1111‘ onL‘c .1 p10 \pL‘Lti vc 11'L'.1l11<.hL1L‘11 lL’>L-1LL'Ll .111Llpitti11g111 1.1'11'11L'l'1ing is i111li.’:11L'Ll. lhc €1'1;111)111\'11l 11l L‘ 111Ltl101'l .1111111 l bCOl'\’l()l.ES\'\llLll LLJ1111111i11g1hL amount of l'1hOii1 nucsnrx 11:11li'; I Hilly Onc short .111L15.l11llt\\' t1L'11L'l1. t1) the Ll iclx .1111lC1x'V .:.1m pling ol 5.1111l1 .wil ’20 -l-UL‘111L'lL‘p.l1.:1nLl .'.'.'.‘1\11:.'1111_r alum 11111. lL'ilLiuiiinolthL:111.11L'1ialL'r)llL‘.1:"1L1l. ALc-ru‘ ”C(lll: 'LLalA mainlitimn. llU\\.'€\“L‘l'. 1:1.1ylcu11l 1L1 crmrx when Lippl V'ing thc 11107 (had in llSLl iniinatel} : A miliacr nut 1Ltpr'L':;L'111i1'.1;tl1clmxilinitiireLilithcmL'lxw.1111 1lcr11L'L11l1. l‘111 truiixpm'Iml {10111 L:_l.~L'\\'hL'1L'. 111.1)! L‘L'tivcly 1)l‘1§1"11I‘C L'vcn thL‘ l'lk‘llcfwt green grnmnluite \lCP\‘.\ll unalcrnL‘uth. in >111'l1 .1 L'usu. only 1:1:(1l0g'icnl I'CdSnIllnlj. <11 wilLl-L'nt pitting and/(11 trenching may he \uL‘LL‘sslizil in finding the l‘V'JCISVl. lvnpnrmnt l5 thc point. 1l1.’1t piml CClg x'huulLl he must intL‘nsivc along Sll'il\-.. la [Orallyi Lil~ .1 01111; 1L'L'ogniu‘1l p1ml111.'tivL' l1<11i7m1 lien is the lJL'xI cl11‘1cc t<> {ind 11111. re L‘nri'Llic l parts lnLlirL‘ct methods l‘m' grccngrosxnluritt' pmspcuingrnny h1: ()l.\ which 111.1V L’LJ111‘L'1\'.1.>lv Luntrihntc- i111l1.11lL' .1 v H'lC’. y ml. :_;c1.>LhL'111i1.’.1l :1111l cnplwsiL .11l 111'1ispL1 tinu tCk'lHllijil k.\. lliL‘. l.l.\L I11 111inL1 1h “"101L11cin.1\\111<1'>L11\L'.15511Li.11clwiththe '1'.r1l111§l1.1l011\‘i- [UllillL‘llt t;1vu'.1r.1i'alL- lUl .11141'1'. Lgi'nx'snlniiL' LlL'pmiLs l..i111li1‘;1(or111i111'r'.1l> applim 1l1L" sar'iL-pr.11.tiL'L's .150111li1161l.1i'.1>\.'c l111'1lieLli1L-1'1 5c1r1l1..\l111L'r.1lx whiLh 111.1v he L'onsiLlc- 1'L'Ll111i11LliL'ALc grL-cn 15.111101 111.19.111.11 are: ...... vphltnv. 1'l1l1)r11L', Z'l?\lf1.‘. ttL'n'mntL'. Ll11>11\.1.lL-. L'K'C'L.‘1‘11.\11 11111'\..1>\'111- ‘l-iighxitﬁ". L‘L‘n 1:.)1:1'111.'1linc. ,o W. l’ohl {k (i. Niederniayr

'l he iiirst minerals indicaic the calesilicare environment. while the two last oiit‘s rt» llect the elevated traceanetal tontont in the rocks. ..Indicator rocks" are Sull‘itlt‘ri'it‘li graphite schists and gneisses. preferahly with mar - He and. talcsilit:ate liandsand’or houdins. Unfortunately. these rocks as well as the in, dicator minerals are little resistant to weathering. They will hardly he recogni7ed in natural outcrops. but rather in pits and trenches. Geochemical prOspecting methods may contriliute during a first. regional stage of prospecting. when areas ofihigher trace metal background are heing south. This is coir teivahle within a large scale prospecting campaign. but will contribute nothing once a prospective area has hecn recogniyetl. Similarly. geophysical prospecting methods might he used to locate the graphite rich rocks. Applicable could he aerial electron‘iagnetics (graphite 1‘. aerial radiometrics {higher uranium hackground in graphitic roclx's‘, ground electromagnetics. resistivity methods ground radiometrics Although an application of these methods may be useful in large. virgin areas. they cannot be recommended generally. Geological mapping may in many cases give the same results. although slower. and will in addition produce a wealth of useful data. which may he quite important at a later. more local stage of prospecting and mining. A possible program for a green grossularite prospecting campaign could consist of the Following phases and activities: 1st phase 7 choosing the area Work during this phase will center on scanninpr geological reports and maps [available from the Mines and Geological Department} for the location of variegated graphitici’carbonatic metamorphic rocks. 2nd phase regional prospecting The area considered favourable from a general literature survey may now lie prospected h): aerial geophysical surveys. regional geochemical ground surveys. liy car and foot traverses in order to locate siutalvle host-rocks. indicator minerals. and. though not to he excepted at this stage. green gros» sularite. 3rd phase detailed prospecting The prospects found liy earlier work now have to be subjected to (li‘tillr led search for green grossularite deposits. Methods used would he wetisie- vine of soil samples. pitting and trenching at regular intervals wherct-ver chips Of the mineral have been found. Every greeingarnet occurrence lo cated will primarily he developed along strike. in order to get data on the location of the richest parts. This phase of detailed prospectinpy will pass into mining. whereever marlv etal’de material is encountered.

-7i..i.—l‘ Mining of green qrossularite The nature oi the deposits oii green grossularite predetermines the possible nieth oils ot‘i exploitation. Restraints are added in the area by the absence of abundant and

\‘llCdp “dill-CT. Present conditions in the area allow the application oi. simple ope-mph and under Mwatate Quadrangle -tt

. . , . . ,_ gmund-' n: miningIT.|.“.||‘.L‘ methodsI..L-?I| J\E\ only.- |||'\'. TheJlu' resultingnut. labour-intensiveness, however, cannot a priori be considered-i asn aaiimlu disadvantage in a developing country. The careful obsem- tion of almost each.l. shovel~.|-.-.-\--| of.' material while being handled will ensure, that no materid of value is lost. Heavy earth - and rock-= _~. - moving1mm: equipment would of course allow the quick removal of large quantities 1-.:.:-.-I:r!-'..of overburden, and in this way a much higher production could\{J'.J|i|. certainlyU':!.J::‘.]'. be achieved..|.]'.'|¢"\-T'.i. TheTil-J reaction!-'.ui'.la]1 ofI-Ir the'hc overseasI'YI' -.I'- market]I‘-.'.Ir-l'1 for1|}? the gems, however,h,,-._ might be unfavourahle to a large quantity of.-?1:‘1v|n.1‘.y-I the material.I Exploitation|~.'.‘J--I[.«['.-a'| of green-. garnet--. from: : deposits. uaw in|.'. thethy MgamaMindiE\-1.,'.1:1:-_ \1:n.:' area.-.:u-.| involves:mnixa; the'- following:VI --H -'\‘.'|!1.-' steps:“ICE" - removalJi‘li: of overburden/or driving" .- underground'.JH.|:-r;-Ir~-II':-.! alongdamn; the productive horizon - mining of the rock containing‘ greenL‘R'n'll gmssularite'.-' *.\LJ'L'.[E"." I - preliminary sorting';51._' to removeI-,'J|.|“.'L‘ largerLEL'L'.’ nodulesIl' |I1'.||.L"~ orl'rl aggregates.Iglﬁl , of green garnet - (wet) sieving of the15.-- fmerMIN: materia1,remod|!..l‘.L"‘.-:]‘ 1.3: :u-‘ml ofMI thegrainI!” size - 1mm, sorting out all green gmssulariteEllt‘ grains,‘l'. and.mf. chipsLIT-u - cleaning of the greenL']r'1‘|| garnetL -.. frommm it'sH matrix:a..|"1\ (tools'I‘-r.-|-- usedHam! maymu beEu a smallnnml] ham-law: I mer, chisels, printers, wire{' brush,I'[|'.' etc.) - sorting of the green grossularite';'|\I"-'~1|].J"Hn' according.I. . I-I'Jiruﬁ toIn colour, transparency,1:.|]|'\‘|‘..I1.!1l". and size. Well crystalked specimenlllu'H may“:IJ‘.' fmd!i[:._ al|'-L'['.L{ better detamonglam-nu mineral{11: ' collectors, and should not be!'-L‘ destroyed-'.1‘».r:l ‘. before a careful evaluationill“ as.1“ to[-.' where a higher re- turnr:'. may:_J n beI‘L' realized.null-1.19..

7.3.57,1,3 MarketingMJrLcrIn: in ‘ The'I'llc abovelli‘|3'\L’-:|,‘-1I‘l-llll cited production figures11;:1H'21]||.1-.-'I,1'I: illustrate the'i.l difficultyIll”; 1131‘. to produceI asteady sup- plypl} ofwax-.11 well balancedi‘-.Jl.1H|:'-:. qualityIlll.1i}l“ from:'|--|i'. the irregular depositsHim-.11 of.-1-I-.:1"|-..~xl;1.||!il.l1.- green grorsulrite. In orderr.:r: to achieve.lLljil'lI‘ theIIIL‘ best‘FL'H' prices[‘i -L'\ :-. - - a steady supply of reasonably comparable'I'.| ‘zl 1|‘|( quality,.ill.!.i['.. andL.:-.: I ' . . - well sorted"[L'-][1.l-'IL‘I‘.I"51',!I||‘ parcels, not run-off-the-mine'lll: 'lllIIII material",!:,f: I . - - I - I are considered‘:(|-|‘.-‘.11|[|.7 advantageous. Of course both'E: demand.. I'..:iI.'_ -‘-'||.|-J|'.'considerable1| u resources-'.1'\<.\ andIil‘l es--. ‘ periences on the side of the miners. Faceted greengrossukrites with a diameta'li‘.ll|l'c']' ofHI more|- ...-- than‘111': 3': mm,‘.|.-|||‘ or-u1' a weight of' mo-'IHI ‘ . . , re than 3 carats are quite rare, andl.I-::|]1I.1“-! command special‘1‘" '1' prices,'.‘r]- r."~. whichwllh I! are fned”l between[It'fVJCCI'l buyer and seller-i!..'1' fort-=: each-..1.1.1 specimen.~1‘.'- Inn-:1. The[lhn' majorityr- -:- of--I' the[lay gemsL'I:JI1:\-'I. trade at-' the1]]: followinglr-‘H-Iu'id; approximate pricesL' (EuropeanII'.‘ 1‘;.-.I|1H.1'.1r.:;‘.. market, 1977):9:7 good colour poor colour 1 carat 2400,‘r'H' 10i'il kshlcarat'."\|'l.'L.!‘..l| 1-2 carats.ml» 40001mm 300jun kshlurat|\-.||.'\ r.|‘- 2-3 i\.41'.:|\carats 6000[IIEVJIJ‘I - 300ﬁlHl kshlcarat, “lg-Ag

7.425:1 RedRu! Comnduml'ur-.1:1-.lnm (Ruby)l-E |:|\_\" Tiny ains of red corundum (ruby) have been found at the following localities: - 2 !?m south of Alia peak, Mgama ridge (E 180 R). Here, the mineral occurs tp gether with red spinel in a marble horizon within the Lualenyi Member. The occurrence has been extensively examined by trenching to several metres depth, and was found to be uneconomic, as no ruby of sufficient size to be marketah- le was found. - GG3-mine, Mikeli Ultramafic rocks, now consisting of pyroxene and amphibole, are in contact The fvst minerah indicare the calcsilicate environment, while the two last ones reflect the elevated,t” *-"H trace-metalVHJJ‘HHVVH? content in”at,“ the rocks.‘ “r. ,,Indicator'..ii[.Hn.r rocks"rm‘l-u" arer'v" sulfide-rich.r HM‘ I' ’m,‘ graphite schists and gnehs, preferably with marble and calcsilicate bands and/or boudiis. Unfortunately, these rocks as well as the indicator minerals arem, little.F'U resistantw 1mm to' weathering.'.‘.:x,ml1wi::;'. They will hardly be recognized1 m‘- in1' naturaln outcrops, but,' rather1;??w in1" pits'f'H' and‘(HiH'L'i'mt'u trenches. Geochemical{;l'L|L’HL'HHl.l|}\K|D\Pl'\[‘11‘_"Lw\| prospecting methods maymm contribute‘,"If‘.[1."‘11L41‘715i11 during afl 1‘ii'7&st, regionalI: stage’ .: ofv' prospecting, when“ ‘ areas,x: s of"1 hiier.V" trace’l metalw ' ‘"J'f'xufHHH‘JJIL‘“UHH"HH’II. backgroundare being south.ThisHH-i- is con-MW ceivable within1 a largetn“ scale‘3. prospecting'v‘ r ‘_ campaign, butMr'.x')H.wm-llmtx-HMMM; will cmtribute nothing once“use a prospectiveFuhlnmu, area,.:«'.:: hasxlulriiv,“ been recognized.jaw} \ V ‘ -i3 l‘;.4[|‘., L'LHI'II‘V\HJE i‘IHHEH'LHHL ‘I'w,’ 1‘,.N1HV]:\LML‘ L‘ JFJ "ll .77 Similarly, geophysical prospecting methods might be used to locate the graphite-I richililv'nl!‘ rocks. Applicable.“\Ii3'h» (LIB could“Lil"L‘ be aerialU'Il‘ll electromagneticsUIL" 'l“"1lL'Lr (graphite !) aerial.m; i radiometrics1.1 ii mu-tzi (higher uranium background in graphitic”mun rocks).m, ground,VII'NHv]; electromagneacs,LIIJLL'HAHL'ILC a, a resistivity methods ground.rrlrwwl radiometricsunlinnimrh \ Although an application of these methods may beuseful inluge,virgin areas, they cannot' 1111,",‘vl beI :' recommendedI(\"JTHE.£‘[V|iL\i generally.‘9“(‘TII‘T‘QI1\. Geologic4 mapping[HJEWP‘IHS may”1.1V inin many[H.LH'C cases‘ ‘1 “ V givefi the anmsresultr, although7}] slower,4 " and(1,“: will in addition. produce'rl a wealth"i'h of\I useful<3M.] data,lit‘l which may be quite importantvqm T 'V at a. later, more local stage of pmspectingHm; and.l mining.mimny A possible‘-. programpmgmm for1m a.1guru:IH‘AHIJHICpithpulil]: green grossduite prospecting campaigntamp‘kmn‘ could2M1,” consist",7 r off the following phases and1.1m1wr1w activities: 1st phase -choosing the area r . , . Work during this71w phasefl“ s".‘.'1H\,L‘HR‘IUH will centeron sbmmn;ucmmguulgeological reports[up‘n'a and41ml maps:Iggra (available from the Mines and GeologicdDcpanwnt)."Qindi [)PP‘H'IT‘JL’IH forMy the7],; location1w .lrinm of variegated graphiticlcarbonatic metamm-phic1‘ J1 Phix rocks.['Hx RN. 2nd phase - regional prospecting The area consideredH , tux: favourablemilrm 1L fromIIWHIr a gcnstsl literature'nr.;i‘1n'wl1rw,' sumy maymm. nownun. beML prospectedI‘m-qty, 1rd by:‘j, aerial,zmlfl geophysical[a '3;t surveys,'. rcgkmalmgiw", 11 geochemicalQumhullmfl ground‘P’illlll'l.:. surveys,H‘y‘g".’_ byl‘ ‘,‘ car£7.11 and'i‘ i footh)": traversesT: f‘L‘»| inorda‘. tolocate"C siutable“hitflblt:lllk‘grr!I:ILrl-\‘x host-rocks, in- dicatorHm] minerals, and, though not’ to1' bel‘ excepted at this stage, green gros-J“ sulrite.Hiring 3rd phase - detailed prospecting The" prospects1‘: found by earlier work'w! nowmw have to' be subjectedI} '1 to detai-'i led1 search,H for green growlarite deposits.1 “ b: Methods wd'l would " 1‘.‘J}‘L be wet-sie-' E ving1' of‘1 soil samples, pitting andMM trenchingtwn‘ Him: at‘1', regular:«';:111.1: intends'1-1rc'z'\'.;“‘- whereever1-,.‘uuz chipsMn ofr": the mineral have been found.‘HL Everylmxvvu‘lm" greengunet occurrence' rm“ located'IJ will'i‘lv primarilym- be developed‘EJ‘HJIIL along strike,‘TH‘m.w‘~ in order to' get data‘Ev‘w‘ on the“u locationI ,Jii‘ w" of the richestr: parts. This'Hz; phase' of detailed prospecting1'1. will2:“:‘HHLh’w'1H"::Hy_.v-gmyx-w pass into mining, whereever mark-.1. etableup v materialu - is| encountered.‘ ‘ n 1

7.3.4II MiningMmmu ofn1} green‘(LL‘H grossulariteu’uvmlmm TheI'iu- nature11.1mm; of the'11: deposits' oft7 greenF‘ grossduiteM predeterminesw. mm the possible methods of exploitation.‘Ir-UHUDH. Restraints.w arew added‘iw in the"M area byn the. absence of abundant and‘i cheap water. Presenty , conditionsEr: ‘ inm ther ‘ areaI allow‘ ‘ the1 application of simple1 open-pitv ‘ and under- Mwatate Quadrangle 47 ground mining methods only. The resulting labour-intensiveness, however, cannot a priori11~1 be considered aii a disadvantage in a developing country. The careful observation‘21 of almost each shovel of material while being handled will ensure, that no material'11.11111.11111.'.111;.1.11111 of value is lost. Heay. earthL'.‘[:' - and.1"1: rock1'11 - moving‘111.1VH'1..‘.111 equipment{‘1111121'1‘1'1‘..11“11")1114111'1‘.111L'L"lil1\lk' would of course allow the quck n- mod of krge quantities of overburden, and:1111111111}: in tlus way‘1'1;‘. a1 much*111111 higher1L1L1I1‘: productionr1111?! 1::-!' could certainly be achieved. The reaction of the overseas1- - market1" 11m! for111 the‘.1«' gems,'-'11:~ however, might be unfavovrpbk to a large quantity of the(1"HJ1' material. Exploitation of green garnet from deposits“"11111‘ in111111111‘~.‘11:.121,11'\1111.11..:1u- the MgamaMindi area involves the following steps: - removal of overburdedor driving-'.111.11.-1_g.-1111111 underground along11111131111 the productive[3:11; horizon1' 1 - . . - mining1‘ of the:11 rock containing~1111.1.111.; greenJUL’L pssutrite51.1w 1.11111: - preliminary1 sorting to remove lvgu1111111: nodules11111111:1. 1 or11: aggregates“.1211" of1 green,_',1u1'1 pet.1: 1 - (wet) sieving of the fmer”1111: mated,111111L131J1.13111112.“ removal of111 the1111 pin.11111:1 size - 1'- mm, ' .17.. sorting 1.111111”; out1 i 1 all green grossulvite‘ grains«21:11 and1x11111!111111 chips - 1 - cleaning of the green1._1111_-'. garnet from11 11 it's1 ma& (tools'1111 used11v.111*11u may be1'1. a1 small1111.111'1xt‘; ham- mu,11111.-1~.1'11<~11:1 chisels, princes, wire bwh,1 etc.) - sorting of1' the7.11; green__':1.‘L‘.'. grossularite__'1'11\--111.1=1'11 according1,1 1'111'1; m7.4 colour,111111'11'. transparency,11111151311- '11 '1', and.11111 size.\ih'. Well1.1»"u1111\\1.11|1.111 crystnllined specimen11-111'11‘111'1‘11 may fmd[1:111 a111; better market'1' among‘11111-'1._: mineral..111111111_11{111-. collectors, and should not be destroyed before a careful evaluation as to where a1511L11c151- higher re-

turn may be realized.,.

7.3.5. 3: Mvketing\hlkuring

The'11-1'11‘.111'1‘.'t"1_11.1'1‘11"11111‘ above cited production111111111; fwesillustrate the111: difficulty1111211_;11\ to11 produce:111111111_ asteady11-1111;\:1}‘ aup- ply of1151L'1111‘.11..11.1.i well balanced quality from the inegulv deposits of green grossutrite. In1:: order-11.11-r to.r_1.-_._11'11:'..- achieve the111- best111:2: prices".11u-1 - a steady.111'1 supply'11111‘11-1'11-1‘1‘ of reasonably111111‘.\'1.11111I‘11111‘11 comparable quality,_.111.1111‘1 and1. - we11.. 1 sorted1|:11‘11;'1.111.1'11-1.11111111':111-111;1111:'11_-11'111111.11 par&, not run-off-the-mine material ' - 11 arei considered11‘ 1L'11'11 advantageous.11\'1:"'.11._'"' .11‘ Oi course1111_1 both1111_ demandL11.111:1 considerable11 1h.“ 1‘" ‘11“' resources":I1:' and:' 1. ex-\‘_'\'- periencesr‘ ‘1::.\ on-1:'11.:1E11 the side of1’111_1:111.1.~ the miners. Faceted greengrossulariteswith a diameter of more than 3mm, or a weight of mo- n than 3 carats are quite rare, and command specid prices, which arc fwdbetween buyer and seller for each specimen. The majority of the gem trade at the following approximate prices (European market, 1977):

good'11111111111111' colour poor[1111111i1111111' colour 11 carat11":1 2400:1-11‘1‘ 101'11..\111.r1:.1‘1 kshlcuat 1-2' _‘ carats.11” 4000‘, 1:111 300'-',1'11'1 kshlcarat1\~11-"1.1r.-.T 2-3.1-..11'.'. carats 6000"111111 - 300“"15-1'1'q17'11 kshlurat 7.4 Red Corundum (Ruby)

s of red corundum1'1 by)‘1 ‘ have11111) beenL found111 at411.‘ the following111‘11'.‘ localities:N. . 11 , __ , .‘ 11 ,, ; . Tiny- 2 r-m south of Alia peak, Mgama11.11-111111..1 ridge (E1 18011‘1111.111-_- R). Hen, the1111.1 mineral:11--1.1|11.- occurs.11 together with red spinel1 m1111111.1‘111311111131: a marble horizon within,t1'11111'111 the Ldenyi11‘-11-11‘.‘1 Member..\-1:!1|11‘! The occurrence11".1 has111 been111.111: extensively.1' 11x1,-11y-1_ examined111-1': by trenching to several11 metres depth,11.‘ and1111. was found'1 1' to be‘1 uneconomic,‘ k11:111"‘1 as1 no111 ruby of sufficient size to be111111. marketnb- le1 was found. - GG3-mine,:11 1 1 Milreli1' Ultramafic1 1— 1‘ 1 rocks, now1. consisting1-1‘ of pytoxene11 1 and amphibole,1 arc in contact< W. Pohl& G. Niedermayr

wlth felsic rocks. In the soil above the contact, tiny chips of red corundum ha- vq been found. Extensive pitting to examine the contacts at depth remained without success. - 1 km north of GG1-mine, Mindi (P 1097 R)

Ultramafic rocks similar to the ones at Mikeli. are cut bv minute veinlets of &"Dee- matoid nature. Red corundum and'- spinel'..1 (?)in very small grains occur in these veinlets. The occurrenceV‘ has been prospected" '-. x by trench' prnlng to the hed- rock, with a negative result. l;p"d ' ' - 1,5 km south of Kambanga1‘ (P 11341I - 36.>v R) , A pit has been opened here to a depth.. I‘M. of 6 metres in graphite schist with bands of marble and cdcsilicates, as well as' pegmatoid'~' 1., segregations. During this survey,

red corundum could not be seen in theI' pit;'. Ii fragmenu were locatedon the dump, however. Although ultramAtes have been mapped1: ' .| at a locality only about 2 km along strike to the northwest\A. (P 1131 - 33.~ R;._ here without corundum), such rocks could not be found inAM the diigsnear Kambanga.M It is nssumed, that the chips of eem-corundum- found on the dum~.orkinared - from the marble bands. In spite of the non~conomicresults of. allx- prospecting for gem-corundum in the Mwatate area until now. further work is certainlv recommended. Until now.. onlv, a few occurrences of ultramafic rocks have been found. It may be expected, that with additional finds more prospectsu 1‘ and possibly deposits of the Mangari type (see POHL & NIEDERMAYR 1977, for more details) will he located.

> 7.5 Other Coloured‘nvw GemstonesH‘HI ‘ In addition to green grossularite and red corundum,V green tourqaline, red pet (rhodolite), blue zoisite (tanzanite), turquoise, and redl spinel have been found in the

Mwatatel" sheet> area. Green" ' v 1y tourmaline is common throughout the Ludenyiw -‘ Member, where it occurs in numerous pegmatoid segregations, and in pegmatitea.14‘”, Toi the knowledge of the aut- hor, only a very few pockets of green tourmalineml”) have been mined in the area. All occurrences known are toosmall and too irregular to be able to support a proper exploitation.

l'H‘ Redl;“i garnet‘ (rhodolite) is exposed in a small pit in the northwest corner of the sheet, and is widely found on the western flank of Mindi. The stones are invariably very small and rarely of reasonable quality. Therefore, they could not be exploited and

sold‘ at a‘ profit on the market. Future, better fmds cannot be excluded. BlueMmm zoisiteW (tanzanite) occurs in minute traces at Lilani. There, a thi& marble ho-

1 rizon forms‘ ‘H an open syndine with graphite schist in the core. The marbles contain concordant pegmatite, lenses with green tourmaline; impure bands in the marble are rich in grey zoisite and show locally tiny blue grains of tanzanite. Extensive trenching at the locality did not reveal any economic accumulations of the mineral. Turquoise forms thin veinlets in ~illimanite~aphitegneiss at Kavishoi, north of Mindi The occurrence is very small, and the minerd rather pale coloured. No economic signif~cancemay be attributed to the fmd. Red spinel was determined mineralogically in the marbles containing red corundum at Mgama Ridge (E 180 R). No economic value can be attributed to this occurrence. Mwatate Quadrangle

7.6 Industrial minerals Under this heading.graphite, crystalline limestone, apatite, and kyanite/sillimanite can.m bez .. listed at. present.;':l ‘ ‘ , . Graphite(y'Jl‘t‘ isI commonm throughoutM the‘ Lualenyi Member.".161; ‘w Bands‘ rich1 enou~hw ,1: inm the| mineralLun‘w»: to warrant miningw and concentrating‘ _ areAr" rare, and' too‘w‘m thin to supporti . anH.‘ openr pit- r operation.x‘ ForI‘ underground1 ‘ exploitation,' ‘ the1: contentsf ate:1 tooW small.‘. 11 No‘w‘ explora-I tionn effortw, forr, thisr mineral‘ , canH be‘ recommended.‘Vwr'wr 4 Marble\‘LIIML (crystalline‘ 4 limestone) occurs‘ throughout‘ M the‘ Mwatate“ n M area,‘l and‘IH could‘ 1 he, exploitedii , at‘ many‘ localities.‘ , Generally,r, a‘ high Magnesia-contentM ‘ is 1 robaH able,1} for mostI l ..;rof the‘ occurrencesv. in the‘ area.,,_ If“ chemicallyM m pure; ‘ limestoner should. ‘1‘” be neededu,“ for a future' Y' 7,},, project,v.‘ y, ' detailed' ,‘x‘' prospectingJ g 4 7 should“L be, carried‘ out. , I -1 ‘ KyaniteRummy and1m! siuimanitexﬂlrnum'm; as‘7 rack-formingn ‘ ‘ " 1.‘ minerals:: ‘1 are locallyIn M developed\ ‘ at Mgama$41,”; Ridge.MIL: There,Z‘vlr' contents"M‘ mayw", reachH ‘1;‘, 10 %‘ of"‘ the rock‘ mass.:. The\ vN-M'H‘ extensions"‘-w1l!‘r‘ of the alu-2“ mosilicate. I‘I.y l'r strata arem too small‘ for| ‘ any exploitation. Sillimanite occasionally forms pocketsL_ inin pegmatoidHM” mobilisates“H. (NN 121 R) which are of mineralogical interest only. At Zongoloni,‘l 'M kyanite‘ (-muscovite)I ‘l vA pods occur in quartzite. Unfortunately, the hard country rock did not weather away as at Murka (west of the Taita Hills), where rich secondary accumulations of kyanite boulders supported a sizable mining operation. At Zongoloni, the size of the pods as well as the frequency of their occurrence within the rockmars are far below economic limits. Until now, the pods have been superfici- ally prospected by locals who suspected the kyanite to be aprecious mineral. The present survey excludes any economic potential of the occurrences, except possibly to supply a small collectors market. Apatite was recognized as a primary accessory mineral mainly in the graphite schists of theLualenyiMemher, but also in theMtonga-Kore Charnockite. Occasional- ly, as at Mgama east (P 1028 R), thin secondary coatings of apatite appear‘E"}""' in joints of graphite schist. Similarly, turquoise fdls thin fsrures in graphite-sillimanite gneiss at Kavishoi. Contents observed are less than 3 %in all cases, to that no further work can be recommended.

7.7 Ores Ores at present known in theMwatate sheet area are of minetalogicalinterest only; they include magnetite, pyrite (with base metal sulfides in minorIAHIIHJH‘ amounts),,..:n! and tuti-Ili‘i' le. Locally in the Lualeny~Member, elevated geochemical values of Uranium and Tho- riumH't‘I. areJIL‘ present.i‘ivmuw Magnetite\1.agm>tm was”x foundt~1:.:1‘H‘ in lumpy awegates in pegmatitic float at Mtonga Hill. It occurs. also‘ as1 anH; accessoryr to" a content of several percent in the charnockites, and the fme’V‘lll" blackhi sandm4 derived‘iﬁjl‘w ‘ fromH those rocks characrerises the soilcovered parts of the complex.w! I‘ SimilarHHJHM thin’~ streaks‘. m of black sand were observed about 5 km west of Mindi overm severalL, ,J square kilometres;1 my! due to the total absence of outcrops in this area the derivationin g, H of‘E this magnetite'm ‘ cannot be ascertained. A specimen of magnetite from peg- matiteI x‘ at MtongaIM'M \v HillH‘ was analysed by the Chemical Laboratory of the Mines and Geologicall , I L VMWI Dept., withM thethr‘ following resultsL‘ (figuresL inH ppm):; Ni Cu* Co‘w Ct\‘r V'\ Znin P1’1!!~.‘ 1089 90MM 151 7 5V 63' 7‘ 700MU 16500,11.'.I‘II'|_

NonH of' the occurrences1 mentionedw possesses' any economicn potentialv W. Pohl& G. Niedennayr

The CIDA aerial magnetic survey has located a strong magnetic anomaly centered at Mtodga Hill. Rom it's shape, the source of the anomaly is considered to ly at considerable depth. Accordingly,tbenature of the source cannot be determined withcertainty. It seems however, that a considerable accumulation of magnetite would be the reason for the anomaly. Deep drilling could certainly Jucidarc the case, but the eco- nomics of mining iron ore at depth do hardly enwurage such work. Pyrite is ordinarily oxidiied at the surface in the Mwntate area, and with the exception of a few localities (P 1015 R - Mgama north, and P 1126 R - MindiITree HouseHill, etc.) only gossanous float points to the occurrence of sulfide - lenses and/ or suKde-rich rocks. Except as a very minor accessory elsewhere, pyrite is restricted to rocks of the Lualenyi Member. Tables 5 and 6 (chapter 7.2.2) show that the sulti- de lenses probably contain besides pyrite sdamounts ofNi, Cr, V, Co, Cu and Zn- ores. In view of the small size of these lenses as well as their wide spacing within the rock-ruite they are considered to be without any economic scope. Rutile is widely distributed as an accesory in the rocks of she Mwatatc quadtan- gle. Only at Mgama north the mineral was found in more than microscopic amounts, however: At the sample location P 1009 R rutile occurs in rounded grains together with qmzin calcreie; it is thought to be derived &om a pegmatite u*derneath, while the calcrete oripinates from marbles immediatelv adiacent to the localitv. At the sample location P-1061 R on the east slope of &Hill, Ndle f& int&anuhr spaces in a pegmatoid granitoid gneiss. Both occurrences of mtile are of minenlogi- cal interest ody. Uranium and Thorium are thought to be present in higher geochemical values in the Lualenyi Member of the MgamaMindi-Fomtion. Actual analytical determinations of the metals have not been carried out, howera, due to the nonavaitbility of the necessary analytical apparatus. On all traverses in the quadrangle, a spectrometer was.carried along to discover. '. '\-'L' : any surface radioactivity. No economically promi3'i concentration was found. The CIDA radiometric survey in the gembelt area was originally designed to help define areas of more intense K-metasomatism, which were thought to possibly coin- cide with more frequent occurrences of penetrating pegmatites. Analysis of the data showed, that K-metasomatism is nearly ubiquitous in the aree K~~highs and lows are dependant on soil and rock types, but do not indicate accumulations of pegmatites. In spite of this failure, the survey discovered a number of U/Th+nomalies, mainly situated in graphite gneiss zones. The evaluation of these anomalies is not yet concluded. 7.8mu Waterm.” - by.w W.‘3‘ J.I NAUTA (AUSTROMINERAL Ges. m. b. H., Vienna, Austria) Hydrology:m 3.1.105“. Surface water in the area mainly originates from the Taita Hills by means of the Mwatate River, and to a lesser extent from the Burr River, which flows along the western edge of this sheet. No constaqt river gauging records exist; occasional mea- surements eive indications for minimum flows of a few liters wr sec. in the northun- most sectio-n of the rivers in the dry season and maximum dows of close to 1000 I/ sec. in prolonged wet rainy seasons [this does not concern short - period storm run- off). No reliable rainfall fpres are available for this area. Extrapolation from nearby Mwatate Quadrangle 51

stations give annual precipitation rates from 400 to 600 mm on the peneplains and slightly higher values for Mgama Ridge and other hills. Bvaporation from open water surfaces is well over 2000 mm per year. Rainfall in the area only occasionally hpro- ves the water situation by fdinp, isolated waterholes, from where most of the water evaporites. Rain on the hills runs down in gullies and rapidly dissipates in the accum- mulation pediments around the foot of the hills. In the Mwatate R~vera dam was built for the Taita Estates Ltd. This dam had a designed storage capacity of 900.000 m3.~urtherdownhum a few very small dams exist. In the Bura River a dam was built for the Taita Hills Lodge, designed to a ston- ge capacity of 190.000 m3. Hydrogeology: Groundwater m the area in general occun in the valley fd (alluvium) and dey connected fmure systems in the metamorphic rock. The alluvium is shallow and very clayey. Therefore groundwater recovery Gom it is not possible but must be sought in the fault and joint systems which cross the river dey. Further away from the river chances for locating groundwater areremote. The metamorphic rocks have a very low porosity. Only fissures and fractures may contain water, combined with micro intersticescaused by weathering. Karst-type sink holes have been observed one some hills with marble outcrops. In view of the low relief of the area it is not probable, however, that larger reserves of trappedwater codd be tapped. In addition, search for such water would prove to be most difficult and very costly.

Boreboles : In this area 18 boreholes have been drilled. Of these 14 were sunk by the Taita Estates Ltd., many of them in the direct vicinity of the dam (table 7, and fq. 13). Most boreholes yield water with a certain degree of mineralization, some nearly fresh, some completely saline. Yields are &able but in general moderate to low. On- ly from the more recent boreholes chemical water analyses are available. Many of the older holes have been abandoned. Table 7 shows that in most of the boreholes water was struck at more than one level, probably due to the borehole crossing several indined &actwe zones or more weathered rock. Mineralization of groundwater (salinity): This is due to weathering of the rocks and the relation between macro and micro pores systems. The mobility of groundwater in the metamorphic rocks is mainly determined by the macro porosity of the fissures, because of the relatively short contact with therock mineralization remains low. The water in the miao pores is of a very low mobility and becomes strongly mineralized by taking up salts produced by the weathering processes. Pumping from a new borehole first draws the mobile water from the macro pores. Subsequently, if insuffi- cient recovery time is allowed, the micro pores will start yielding mineralized water to the maao pores systems, thus gradually turning the pumped water saline. Geophysicalt..-..1-".~""' prospecting: Electxo-resistivity work ha been carried out in the area. Cross-soundings have been made near boreholes at Taita Estates of whlch accurate drill logs exist, in order to ob-

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Nulc 1. A11 depths ~n mclrn.2. USL. w~lcric#uckle~tl.3. WRL =wlrr rru Ierrl:.l. Y 15- C 70 toC 520in'l rreth.014 I -cr hole. thrv po%,r.un.ace .nhmd .n the map but nos rlr iar?~5 o XRA ta1:r2-4 .ncl.uemr ncx ~r~ehnl.~.n~~~rhris p.,c,,n'inddrll.,. lilC..Icr4 I." ,heup

' Tabla 7 - wetel- borchol. rsrord? from ihc Mva~zicqwdisntlt Mwatate Quadrangle

E E E n . E tainspecific| .E. resistivity1 E valuesE ' for lithologyE E E_ and aquifers.E _ Treatment of the obtainedE.EEE re- sultsE revealedEE‘ E. a Lhite anisohopEEE of the resistivityE pattern‘ E" in the metamorphicE "EEE rocks. FunherE ,E southE exploration' work as beenE carried‘ out by electro-resistivitE 1: E E'. sounding E h E _. E andEl rofiling.EE However,I'IEE the exceptionalE ' flood conditionsE of 1978E strongly Lited the wor R. E Groundwater(EI'EEmE-.|\\_;z--E potential:pun-1111.11 AtE this-. stage1. of researchE itE is thought‘ thatE'E. the roundwaterE E E potentialE ofE E theEE 1 Mwa-E‘ E tate Sheet areaE is veryE low,E. both~ quantitativelyEE E andgquzlitatively.u E E 'E E E E QuantitativelyI_.‘ 1E ' . it is low‘. E sincev rainwater11 in the area irwlf hard1E E contributes‘ E toE ‘ any recharge.[E- Most rechargeE comesE EEY_' fromEv Mwatate‘EEE E and Bura1 RiversEEEEEV KE eadwaters,E, ' butE storage along these river valleys\‘._1._VI E isE limited.".‘ Qualitatively\3 it isE lowE H due' toEEEE‘ mineralization‘ ofEH water contained1E" in: theE.E metarno h ic1. rocks, as well as of[ water1 in partsEE of the’ l alluviumEE‘. E becauseEEE ofE. the often‘E highly $a: licI ,,black-cotton"-typeEEr. E' ' I'“E of' soils.

Surface\EI'E_1EE' waterE E: potential:i-IEEK‘HEEEEE.

TheEXE rue[ occurrence ofEE'E flowing._' surface'EE :E water in theE lower'E'»_ MwatateEEEEE 1E andELE‘EE BuraE River valleys is no basis forE EE the'E development«EEEEEEEEEE of'E reliableE E EE waterEEEE supplyE‘\ systemsE EjEE, from'EEEE surfaceEEE water. EvenE theEEE TaitaEE‘EL Estates andEEEEE TaitaE Hills-1EE: LodgeE EE damsEE in the'EE_.E northernE parts‘1 I ofE‘EE the sheet areE ofE limitedH potentialr l] becauseE_ of’.E the high_ evaporation.E,E TheE E applicability"EEE’EE of existing technical meansVEE 11 toY minimize"EE'EEEEEEEEE evaporation,[_\ ‘E EE like floatingEEE_"E plasticHEE sheets,-'EEE. wouldE EEEEI‘ have to be examined..E

8.E‘EE ReferencesRcEL-rcmc»

BAGNALL,E'EfE-‘EE-‘xE E S.,H 1964:1 Geological'EEwEEE'EEgiEJEE relationships[LEEEEEIEE'EEE11"“ inN..‘EE E.E, Tangan*EEEEEE:.Er:\ 1.. andEEE.E theirtE'EE-l' bearingEE. on--;.I!EE. the granuliteEre'..EE'E'E- problem.[‘7

HORKEL,11'.|-.l i. A., “.11NIEDERMAYR,HI :x".'.."~.\"|{. 1..'.G. A8r I’11i1|..POHL, ‘1\.W., 1979:'-" .-_ 111-3Geology --1of the Taitai 3111!:- Hills quadrangle-.. ':.:.'.;|-. (Sheet“ll-v." 18914)|411 --L - (J1-a.(".1-:1|.11;1-_-|-.1I0.111111:-Ges. Geol, Bergbaustud. Osterr., Wien. MIYASHIRO,‘- "ﬁllll-‘i ". A.,.-\.. 1973; Metamorphism and Metamorphic Belts. G. Allen & Un- l'-' -' '1: ".‘|._-r_.1-: '111'11'1ic11- ..11-l MN. ‘-'-‘-!"‘|_':'; lat-1"" - [" -‘~,I':--; m I win, London. PARKINSON, J., 1947: Outlines of the Geology of-! 1'11;the \1Ei1"Mtito Andei-Tsavo_ . Area, Kenya Colony (with map 1:250.000). Rpt. 13, Geol.£1.‘::| 811:1;Surv, 111of Kenya,!\'1-11‘_.'.1..\.. Nairobi. RAMSAY, J. G., 1967: Folding and Fracturing of Rocks. - McGraw-W,-'\.-‘11(Ir.1\'.'-H:. New"§v".-. York.\I SAGGERSON, E. P., 1962: Geology of the Kasigau - Kurasc1911.131 Area.-'\‘.1-.1 (withWEI}.- two711." maps1:11!»- 1:125.000).!:|.‘ - Rpt. 51, Geol. Surv. of Kenya, Nairobi. S-‘VxI'JJJx'.SANDER, B.,:-... 1948:]'- Einfiihrung in die Gefiigekunde der1 L't'l.‘ll5'..'_l\|l11':'.'geologischen K6rperK1..-1}'v.:1 - Er-i ' 13'1".ster Teil.J'L‘il - Springer,‘3‘. Wien. L91;\SANDERS,.“. | .1 | L. D., 1963: Geology of the Voi - South Yatta Area (with two maps r . 1:125.000).. - Rpt.111-1. 4-1.1..11.54, Geol. Suw..\ . of Kenya, Nairobi SfSCHMETZER,H'V'Il' III/1'“. ‘55..K. W.,'\1.' BERDESINSKI,[11"13. I H R'EN‘HI W. & TRAUB, I., 1975: Vanadiumhaltiger 1..1:-":»~1:|.11Grossubr .1:1~1"1-_-1‘.1..aus Kenia. - 2..3. .31.dt. L-I1-11'11:.Gemm. ti-.Ges., 24,230-234.2-1. .'. " .3!SHIBATA,|l|"1..-’\ l'.-‘~. KK.,. 1975: Preliminary Geochronological[11:2111': Study on Metamorphic Rocks from Taita Hills, Southern Kenya. - 1st Prelim. Rap. African Stud., Nagoya [3111-92.Univ, _72-75. \I‘Jfl'I/J'IHSWITZER, II}.G. K”S., 1974:i"-‘”'-1.'{-1|!".' Composition of Green Garnet from Tanzania and Kenya. - 'ri'i'l':Gems .1115.and 1Gemmology,£1'11-11111l11_.:\. 296-297..1911 TURNER,l'[ 1-3 {QM-1. F.|._|. J. .\& WHHS.WEISS, |..L. E.,|'.. 1963:I‘ir'1 "1: StructuralK1.11;.1'” Analysis of Metamorphic Tecto- nites.1;:;---.. - .\'1\[i:'.1\\'}l1H.McGraw-Hill, New York.Yu-tk. "1‘..‘-.lWALSH,311' _|..J., 1960: Geology of the Areasouthof- theTaitaHilL(wirh map 1:125.000). - Rpt. 49, Geol. SUN.1'. 11‘.-of Kenya,K (”11111. NairobiNiairuhé. WEDEPOHL, K. H.,.. 1969:INN}: [..~.-1111>1.=.~'ili.1Composition:; .11121 and Abundance.-\1*1111:1.1111 ._- of111- r.Common.- 11:111'1111‘. ."1'Sedimentary Rocks. 251-271 in:111: Handbbok}'1.':11-H‘-1'1-'1‘.\ 1'15of [.161'11'11121211511'_\'.Geochemistry, Vol.\-"1\'.. I,I. K. H.H.‘.1.[-|]IPHF|J WEDEPOHL ed., Springer, BerlinHeidelberg..511-1.!r. WEISS, L. E., 1959: Geometry1; 11: of ‘."'.[‘tl:_‘-'I.‘hl_‘l.isuperposed 1111.!1211;folding. - Bull.[‘11I1|_1icr-l.\. Geol. Soc. America, 70,91-106. WINKLER, H. G. F., 1974: Petrogenesis11131111.:«11- 1..-1of 515111.1111111pl111metamorphic 11:11.1“rocks. - 3rd."1:.‘.. ed., Sprin-fir-:11: g-, Berlin.

[11;-UnpublishedIIIII preliminary reports by the Kenya-Austria Mineral Exploration Pro- ject|L'-:' (available.|\'.I:.i.|i‘]£.' .:'at The."the Mines and Geological Dept., Nairobi) :

HORKEL,|.1' -‘E 'i A.--1. a.& ELLIOTT,11.1.11.” 1. D. H., 1976: Geology of the Kangetchwa Quadrangle (SheetKiln-1'3“” 18911).i . - Rpt.54.111. 1.1.30 pp., 5 fqs., Nairobi. HORKEL,Hali-Il\'l_.|. A. & ELLIOTT, D. H., 1976: Geology of the Manyani Quadrangle (Sheet 18912).|-\ - Rpt. 2,21 pp., 5 figs., Nairobi HORKEL,:I" *Hii |'.l A. & ELLIOTT, D. H., 1976: Geology of the Maktau Quadrangle (Sheer 18913).4'1'1 - Rpt. 3,21pp., 5 fi., Nairobi. HORKEL,Hi 1I\'|\l'| A. & WACHIRA, W., 1976: Geology of the Mtito Andei Area (Sheets 1831 14).: ...; - Rpt.;-\' [11 5,52:1. '1'“pp., 121".1'1111‘\.'!...\ annex-fqs., Nairobi. NIEDERMAYR,x11'1.11-111-1111'11. 1;.G. & HORKEL,11:111-1411 A., 1976: Geology of the Taita His (Sheet 1891 -14).. - Rpt.14.111. 4,-1. 65. pp., annex, 7‘ annex-fi., Nairobi. POHL, W.,.\.11111-:' NIEDERMAYR,.-"-.1.-\\I1.1. G. a& HORKEL, A., 1977: &lo of the Mangari Ruby Mines. - Rpt.I‘J‘lﬁ 'il-9,70,.-1I5111. pp., 16|r11-'1.= test-fgs.,‘-1-.--.. 41 annexes,111':-.-\.::-.!1 6 annex-&&, Nairobi. POHL, W. &0-. NIEDERMAYR,"“H'J'li I-I'\'I,-\,‘1”:-.'. G.,(1.. 1978: Geology1.11.... U.- of the Mwatate quadrangle (Sheet 19512)!-"_- __' and.r_.i ther|.1 vanadiumgrossularite'..|11..|,i']1'1;1"-.1-\I |.'.|;11' de osits1.11 of| the area. - Rpt. 11, 89 pp., 8*' text-figs.,-' ':. 3"- annexes,. 5 .11-I11'1.annex-figs.,‘-:_. 1- . Nairoii..‘..1.. . Mwatate'-.‘..;..=L QuadrangleQ IlilllLll'

Find reports and feasibility studies presented by AUSTROMINERAL in late 1978:

1st Report: Results of the Geologcal Survey of the Taita Hills Region - 589 pp., maps, fqures. 2nd Report: Geological Prospecting and Economic Assessment of the Gemstone Belt in Southeastern Kenya - 198 pp., maps, fwres. 3rd Report: Geological Survey and Results of Mineral and Base MetalProspecting in the Coastal Belt South of Momhasa (Kwale D~strict)- 106 pp., maps, figures. 4th Report: Pre-feasibility study on the Murka Kyanite Deposit - 186 pp., maps, fgures. Acknowledgements Personal thanks go to the Chief Geologist, the colleagues and other staff of the Geology Department, Nairobi, whose never-tiring enthusiasm and assistance were the basis for successful work. To the project-manager, Dr. Werneck, we w~shto mention our appreciation of hrs shouldering most administrative and organisational work, thus helping us to work effectively. The Mines and Geology Department, Nairobi, and AUSTROMINERAL Ges. m. b. H., V~enna,kindly gave permission to publish this paper. AUSTROMINERAL gene- rously supported printing of this paper as well as the coloured geological map enclo- sed. During a field visit to the area, Dr. Gabor GAAL from the University of Helsinki, Finland, provided most stimulating thoughts from his wide experience of the Pre- cambrian geology of Northern Europe.