(GEA748|
June 1987
THE URANIUM POTENTIAL OF THE BUSHVELD IGNEOUS COMPLEX
A CRITICAL REAPPRAISAL
Investigators: MAG Andreoli R J Hart H J Brynard F A G M Camisani-Calzolari
ATOMIC ENERGY CORPORATION OF SOUTH AFRICA LIMITED PRETORIA THIS DOCUMENT MAY NOT BE COPIED IN ANY WAY WHATSOEVER PER 158 GEA 748
ATOMIC ENERGY CORPORATION/UNIVERSITY OF PRETORIA WORKING GROUP ON URANIUM IN THE BUSHVELD COMPLEX
Progress Report No. 4
THE URANIUM POTENTIAL OF THE BUSHVELD IGNEOUS COMPLEX
A CRITICAL REAPPRAISAL
Investigators:
MAG Andreoli R J Hart H J Beynard F A G M Camisani-Calzolari
POSTAL ADDRESS: Department of Geotechnology P 0 Box 582 PELINDABA PRETORIA June 1987 0001
ISBN 0 86960 848 7 PER-158 GEA-748
ATOMIC ENERGY CORPORATION/UNIVERSITY OF PRETORIA WORKING GROUP ON URANIUM IN THE BUSHVELD COMPLEX
Progress Report No. 4
THE URANIUM POTENTIAL OF THE BUSHVELD IGNEOUS COMPLEX
A CRITICAL REAPPRAISAL
Investigators:
MAG Andreoli R J Hart H J Brynard F A G M Camisani-Calzolari
DEPARTMENT OF GEOTECHNOLOGY ATOMIC ENERGY CORPORATION OF SOUTH AFRICA LIMITED P 0 BOX 582, PRETORIA (0001)
June 1987
ISBN 086960 848 7 PER-158- i -
CONTENTS
Page
Samevatting/Abstract vi
LIST OF ABBREVIATIONS ii-iii
LIST OF TABLES iv
LIST OF FIGURES v
1 INTRODUCTION 1
2 ON THE POSSIBILITY OF A GIANT OLYMPIC DAM-TYPE DEPOSIT JN THE BUSHVELD COMPLEX 3
3 THE WATERBERG COVER: A TARGET FOR UNCOMFORMITY-TYPE DEPOSITS? 19
4 ADDITIONAL TARGETS FOR URANIUM EXPLORATION 25
5 DISCUSSION & RECOMMENDATIONS 27
6 ACKNOWLEDGEMENTS 30
7 REFERENCES 30 LIST OP IBBEKVIAÏIOIIS
All allanite amp amphibole apa apatite bar barite bas bastnaesite bor bornite bra brannerite car carbonate cat carnotite cha chalcocite chl chlorite cof coffinite cpy chalcopyrite cov covellite dav davidite dig digenite ena enargite fer ferberite flo florencite flu fluorspar gal galena gum gummite hem hematite mi>: microcline mon monazite mt magnetite mol molybdenite mus muscovite Raf albite-oligoclase phi phlogopite pit pitchblende pyr py/ite pyt pyrrhotite pyx pyroxene PER-158- iii -
LIST OF ABBREVIATIONS (continued) qtz quartz rut rutile sea scapolite sen scheelite ser sericite sid siderite sil silver smaltite sph sphene spl sphalerite tor torbenite tou tourmaline ura uraninite urf uranofane xen xenotime zir zircon F.apa fluoroapatite F.phl fluorite-bearing phlogopite Fe.rut ilmeno-rutile REE.F.car fluorocarbonate with Rare Earths Elements (REE) Nb.rut niobian rutile Th.bra thorian brannerite Ti.hem ilmeno-hematite Ti.mt titanomagnetite V.tuch uranium-rich hydrocarbons gel (tucholite) V.mt vanadian magnetite LILE Large Ion Lithophile Elements (e.g. U, Th, REE, K, Rb, etc.) REE Rare Earth Elements t tens (metric) 9 6a 10 years PER-158- iv -
LIST OP TABLES Page
TABLE 1 Uranium Deposits in the pre-mesozoic basement of South Australia
TABLE 2 South Australia provisional copper inventory 10
TABLE 3 South Australia provisional uranium inventory 10
TABLE 4 Frovisional uranium inventory of the Bushveld Igneous Complex and Northern Transvaal, South Africa 11
TABLE 5 K-, Ha-rich granitoids of South Australia 12
TABLE 6 K-rich rhyolites (1-3) and granitoids (4-8) of the Bushveld Complex 14
TABLE 7 Calculation of U,0o reserves in the Vergenoeg Pipe 18
TABLE 8 Comparative geochronology of uncomformity related uranium deposits 21
TABLE 9 Comparati/e geology of uncomformity-type deposits and central N Transvaal 23 PER-15*- v -
LIST OF FIGURES
Page
Figure 1 Distribution of principal uranium occurrences in S. Australia listed in Table 1 8
Figure 2 Distribution of uranium occurrences in the Bushveld Complex and adjacent areas in relation to regional geology and relevant metallogenic provinces 9 PER-158- vi - ABSTRACT
A review of published literature supported by field observations on the uranium potential of the Bushveld Complex indicates that this geological region may host deposits with reserves in the range of a few.thousand tons U.O .
The possibility that the Bushveld Complex or its cover rocks hosts, or has ever hosted in the past, giant uranium deposits such as those of Olympic Dam, Key Lake, Jabiluka or Rossing is considered to be unlikely.
The potential for volcanogenic, caldera-type deposits in the Rooiberg Felsites remains at present untested. Recommendations for research currently sponsored by the AEC at the University of Pretoria are presented. PER-158- 1 - 1 IHTKODOCTIOH
Since 1983 the Atomic Energy Corporation has actively supported scientific investigations on the uranium potential of the Bushveld Complex with the aim to locate target areas for a major uranium deposit outside the Witwatersrand Basin. These studies were conducted by the Institute for Geological Research on the Bushveld Complex at Pretoria University in conjunction with visiting experts from the USA (E S Cheney) and the UK (P R Simpson).
These authors - in view of the time constraints on thtir stay in SAuth Africa - concentrated on a preliminary assessment of the available published and unpublished material which was available at the end of 1985.
Simpson & Hurley's (1986) study is largely of a geochemical nature and predicts that yet undisclosed uranium mineralizations probably occur (besides the Karoo sequence) at the base of the Waterberg Group or as hydro thermal vein deposits in areas with the following favourable features:
(a) Fertile granite source (uranium-bearing proto-ore) (b) High he&c flow to drive the hydrothermal circulation (c) Availability of fluids in the thermal aureole (transport of U) (d) Tectonically produced channelways (faults/fractures) (e) Suitable geological traps to precipitate uranium
Simpson & Hurley (1986) further identified four potential lineaments which transect the Bushveld and host the largest proportions of uranium (and tin-fluorspar) mineralizations. These lineaments would appear to provide a preliminary exploration target for uranium.
The analysis by Cheney (1986) supports Simpson's conclusions, but limits the size of the potential hydrothermal mineralizations, which he considers to be very small (e.g. Albert Silver Mine) in size. While emph-sizing the need for accurate radiometric mapping and PER-158- 2 - regional hydrogeochemical grids oyer the Bushveld, Cheney (op., cit.) formulates five additional potential exploration targets (listed here in approximate order of decreasing priority):
(i) Giant Olympic Dan U deposits in the coarse, oxidized sedimentary interbeds within the Rooiberg Formation (e.g. Cheney & Twist, 1986), or - more likely - in the sediments of the Vaterberg group/Loskop Formation
(ii) Giant unconformity/vein-type deposits (e.g. Canada, Australia) at the base of the Waterberg sedimentary sequences
(iii) Volcanogenic (e.g. caldera-related) uranium ores in the Rooiberg felsite
(iv) Chemical precipitation of uranium that has been leachea froc acid igneous rocks such as felsite and granite
(v) Nigmatitic-pegmatitic (Rossing-type) zones of uranium enrichment caused by the Rustenburg Layered Suite in the roof/floor rocks (e.g. Transvaal sediments, Rooiberg felsite)
A different approach to the problem of the uranium in the Bushveld was proposed by Twist (1986) on his return from a visit to the world-famous Olympic Dam deposit. From the available data Twist modifies Cheney's (fip.. £i£.) interpretation and suggests that an equivalent of the Olympic Dam mineralization should not be searched for in coarse-grained (oxidized) volcaniclastic sequences in areas of graben, but rather in the more evolved granitic terranes. In accordance with this interpretation, the fluorspar mine of Vergenoeg (Crocker, 1985) is cited as a possible Olympic Dam equivalent.
To date no written technical discussion or comment has yet been produced by the AEC geolqgical staff on these reports. The authors PER-158- 3 - intend therefore to analyse critically the above-mentioned prospecting targets to assist the planning of current, short-term research activities at the University of Pretoria.
In this investigation the authors studied in detail the available scientific literature on the Australia and Canadian U mineralizations. In addition, field visits to uranium occurrences in the Rooiberg, Pietersburg and Bronkhorstspruit areas, led by Dr F Walraven, Messrs I Crocker and C Callahan (GSO), provided ample opportunity for discussion and brain-storming for all involved. Some limited petrographical work on selected samples has also been conducted.
2 OH THE POSSIBILITY OF A GIANT OLYMPIC DAM-TYPE DEPOSIT IH THE BUSHVELD COMPLEX
Using data by Roberts & Hudson (1983), Cheney (1986) suggested that the sedimentary intervals within the Rooiberg group felsites could host an Olympic Dam deposit, for the following reasons:
(a) The Rooiberg Group was deposited immediately before the atmosphere became oxidizing or shortly after (b) Fe, Pb, Zn sulphides have been prospected for in Rooiberg volcanics and agglomerates (c) The Selousrivier Volcanics have a sulphidic/hematitic character resembling that of the host rocks of the Olympic Dam deposit
In Cheney's model U leached from the Bushveld granites could have been fixed within those sulphide-bearing sedimentary horizons because of (a) above.
A new interpretation of the Olympic Dam deposit was subsequently proposed by Twist (1986). This was based on direct underground observations, and on broad similarities in setting, geochemistry, age and lithology between the Olympic Dam deposit and the Bushveld Igneous Complex. PER-158- 4 - Tables 1-4 and Figs. 1 and 2 indicate that there are appreciable and critical differences between this giant Australian deposit and the proposed South African equivalent. The Olympic Dam deposit is in fact situated within a major and complex metallogenic province characterized by the association of hematite, U-REE-minerals, sulphide and precious metals from the mid-Proterozoic to the lower Palaeozoic (no's 5-11, Table 1). It is significant that Rowlands (1974) compared the Adelaidean geosyncline to the broadly coeval metallogenic (U-enriched province) of the Lufilian arc, between Zambia and Zaire. Additional U mineralization in Tertiary cover rocks is also present at Beverley, Gould's Dam and Honeymoon (loc. no. 17, 18, and 19, Fig. 1). The mineral endowment of ths lower Palaeozoic-upper Proterozoic Adelaidean geosyncline could possibly derive - according to the authors - from the erosion and redistribution of metals from the upper levels of the Olympic Dam and of similar other deposits (see no 2, 3, Table 1). The paucity of uranium in the Adelaidean is consistent with an oxidizing atmosphere and a consequent decoupling of this element from the other base and precious metals. If we translate these concepts in terms of the Bushveld Complex, we could expect a somehow comparable metallogenic fingerprint in the Waterberg and in the Karoo. The base metals and uranium (Table 4) indications in the Bushveld Complex (with the exception of the U-enriched Karoo rocks of the Springbok flats area) are, however, several orders of magnitude less than in the Adelaidean. This is a fact which strongly militates against the presence of Olympic Dam deposits now or in the past within the northern-central Transvaal. In this discussion we exclude the gold (sulphide) mineralizations of the Pilgrim's Rest area (No. 9, Fig. 2) as unrelated to our discussion.
There are also other arguments against the presence of an Olympic Dam deposit in the Bushveld, although we do not deny that the volcanic pipes of the Vergenoeg-type could reflect ore-forming processes broadly comparable with those which operated at Olympic Dam. TABIB 1 inUUHUH MPOSITS IB THB PP.B-HBSOIOIC BASBMOrf Of SOUTH AU3TBJU.IA
•o* Locality Metala Mineralogy nta letting At» Reference (Ca)
Olympic Fe-Cu-BKB Heet-ura-cof-bra a) Stratabound sulphide oxide Graben In K-rlch ^1.58 Roberts A Hudson, Dan 0 Ag-Au -epy-bor-dlg- ere In matrix-rich breccia leucogranlta 1,81 1983; R. Creaser, pyr-bas-f lo- b) TransgressIve sulphide rapaklvl terrane 1985, pers. cow». '. gold-sll- oxide ore overlying a) at ->f the Gawler Twist, 1986. zlr-mn». centre of graben. Craton (Stuart Qtz-ser- Origin of breccia la contro shelf structural flu chl-sld- veralal (ealdera/hydraulle- province). bar-rut. hydrothermal va. sedimentary).
Acropolla Oil) As (1) above Complex Mineralization akin Aa (1) above Company Prospect as (1) above announcements
Wirrde cu T Pr«-Adf»laldtan b«a«Mni, Company Well likely related to (1) above. announcements
HI. U ftu » Secondary U mineral Proterozole Nawson, 1944 Ogllvle (lleblglte) enclosing gold. sediments (»)
Ht. Fe-U-*EB Hem-ura-mon- (aiol a) Disseminated stratiform K rich leucogranlte Voules, 1975; 1984; Painter (In-CO-Ho cpy-bor eov- mineralization hosted by and gnelas of Proteroz. Lambert et_al., ,»g-Au-Cu chc-pyr-1 lm-xen- coeval granitic breccia. the early mid to 1982. Mn) plt). b) Younger hydrathermal Proterozole Ht. OrdovIc i an m Qtz-mlc-ser mineralIz. Painter Inller. i flu-bar Origin of breccia Is contro This Inller -apa phi- all. versla1 (sedimentary V9. Includes extensive co i hydraulic). U and areas of monazlte sulphide contents Increase bearing blotlte with Increasing primary schlsts.'gnelssus. hematite to chlorite ratio.
locality number In fig. 1 TABLt 1 lconiwn»
•o* Locality Metals Mineralogy ta Setting Reference (Ga)
» Gunsight u Cu Secondary mineralisation On As 3 above South. 1973. Prospect highly «beared stetaaediments and granitic rocks) coincides with Magnetic high.
» Crockers U Th TI Th.bra dav Ore minerals restricted to Early Proterozoic I.SB Ludwig 4 Cooper, well Fe UFR Mb. rut MOn. mechanically (hydreullcal ly) Wlllyama Complex 1984; Ashley, 198«; Qtl F.phl- induced fractures end comprising exten Whittle, 1959. epa Waf - mus- breccias In Ha-rich slve Na-U Th Mb Ce chl-tou flu- anatectic trondhjemlte. Y-F-rlch gneisses MEK.F.carU).** (metamorphosed analelme bearing alkali volcanica/ tuffSt).
Ml. U-Tl RRF. Rut-dav-zlr-«on Lodes associated to Ha rich As (4) above 1.58 Whittle, 1959, Victoria Fe sen hesi-Ti ml- gnelss/trondhjenite. Davidlte Ludwig and Cor per,, pyr cpy-ena. occupies fissures apparently 1984 Bio- sea qt* formed by brecclation during chl-ser-Nof shearing. apa sph all.
Mad tin* II REE Ti dav rut - Ti . sit- Lodes In structurally con- As (4) above 1.58 Hawson, 1944; Hilt Fe Sc-V Tl.hem.-re.rut- trolled fractures near contact Whittle, 1959; Cr » V.mt-heaK of Na-rlch trondhjemlle and Ludwig and Cooper, m pyr-cpy-mol. gneiss. 1984; Parkin, 19*5. w I r.phl-qti-chl- Cr:V:U- 1.5:1:0.3 U' ser-car. (stole prop. In ore) i
locality number In Fig. I I: trace •o* Locality Hatala Mineralogy Setting •afaranca 10 Thacka Ti Fe-U Oav Minor dlasemlnatlons and Aa <»> above Johnaon and Cow, rlnga RRK lenses aaaociatad to pegmatite Uillyama complex. 1975 (H.S.W.) and retrograde aehlata. Thara ia no known economic minerali zation, but U O in borehole water averages 25 ppm. Indicating enriched basement. Nnonta Cu Fe Ho- Bor- epy-pyr- Shear zones in baaeaient Schist, gneiss and T Mawaon, 1944; Wallaroo Au Ag U- pyt-hem-mol- mineralized by pneumatol Ulc porhyrles of the <1.«5- Dickinson,1953a. Pb-ln Wo gal fer-ach- fluid» of likely pegmatltlc «Id-early 1.55 ma-gold ail- derivation. Proterozolc U.tuch. Relatively high radloaietrlc Gawler Craton. Flu-tou apa anomalies extend between pyx/amp qtz. aeparatad sulphide mineral 1zed zones. Cow©11 Small concent ratlona. Precambrlan rock» r Mawaon, 1944. of Gawler Craton. 13 Port lira gum Small reserves of U O- in thin Pracambrian roeka t Johns. 1975. Lincoln concordant bodiea/ataaply of Gawler Craton. dipping tabular bodies in granitic gneisses. l«/is m. Lofty uniki Dav pit gold Small U deposits with minor Alhltite, K rich t Thompson, 1965; Range PF.R Cu, Au in =o.mu,oÉ. locality number in fig. 1 PER-158- 8 - in- 196" 140* SO 0 50 100 150 200 Lake Eyre-*~^ V> South C^ Broken Hill Willyama Block URANIUM OCCURRENCE IN TERTIARY COVER URANUP OCCURRENCE IN BASEMENT MESOIOIC TC RECENT UPPER PROTERCtfOIC TO PALAEOZOIC \ | LOWER TO MIOOLE PROTEROZOlC I j GAWLER RANGE VOLCANICS |1.55-1>5G«I ! | ARCHAEAN RELICS 7 METALLOGENIC PROVINCE Fig. 1. Distribution of principal uranium occurrences in S, Australia listed in Table 1. Geology and distribution of mineral occurrences after Ellis (1980) and the maps published by the Australian Bureau of Mineral Resources. M"| 27* 2">* 31* 2S*E i 22*S ( rB <: r > 2*' L egend \ \ PERMO-TRIASSIC BASINS llv^j WATERBERG 6R0W 26* [{vX-A POST lfCTONIC IGNEOUS ROCKS I 1 TRANSVAAL SEQUENCE AND OLDER I J ROCKS /^va\ BUSHVEID IGNEOUS COMPLEX MMALLOGENIC (_ ,* %J PLACER DEPOSITS WO 200 dm ?s* 2 7" 11" Fig. 2. Distribution of uranium occurrences in the Bushveld Complex and adjacent areas in relation to regional geology and relevant metallogenic provinces (after Hammerbeck and Allcock, 1985; and Crocker & Callaghan, 1979). Note that scale of Figs 1 and 2 is approximately the same to facilitate comparison. PBR-158- 10 TABLE 2 SOUTH AUSTRALIA PROVISIONAL COPPER IWERTORY District/Mine xlO t Cu Refer. Olympic Dam >30 000 Roberts & Hudson, 1983 Mt Gunson ~ 100 Xnutson et al., 1983 Mt Lofty Ranges 72 Dickinson, 1953 a Moonta-Ua1laroo 336** lickinson, 1953 b Northern Flinders Ra. 11,5 Dickinson, 1953 c Total 517,5 (Excluding Olympic Dam) Mines closed; figures indicate total production Au, Ag recovered as by-product TABLE 3 SOUTH AUSTRALIA PROVISIONAL URAMIUH INVENTORY Mine/prospect t U* Reference Olympic Dam >1 000 000 Roberts & Hudson, 1983 Beverley 11 500 Company announced, 1983 Mt Painter 6 200 Battey and Hawkins, 1977 Crocker's Well 5 000* Ashley, 1984 Honeymoon 2 900 Comp. announced Radium Hill 1 7000 Hartley, 1978 Total 27 300 (Excluding Olympic Dam) * In situ reserves; + Cut-off depth : 100 m # Figure is production between 1954-1961 ; remaining reserves negligible. PER-158- 11 - TABLE 4 PROVISIONAL URAHIDM 11VU10RT OF THE BOSHVELD COMPLEX AMD •ORTHERH TRAHSVAAL, SOOTH AFRICA Ho* MIWE/PKOSPECT t 0** TYPE 1-2 Springbok Flats <60 000 A... Epigenetic in Karoo coal 3 Palabora H. <10 000 ... carbonatite 4 Albert Silver H. < 100 B... Vein-type 5 Bierman-Roux < 150 ... Upbearing quartzite in gneiss 6 Pilanesberg <60 000 C... Alkaline complex 7 Groothoek/Doornrivier <12 000 D... Stockwork 8 Vergenoeg <11 000++ ... Volcanic pipe * Loc. no.'s shown in Fig. 2 ** Data supplied by P J van der Merve, pers. comm. A RAR + EAR resources in the $ 80 - $130/kg U cost category B " " " " $130 - $260/kg U cost category C " " " " > $260 kg cost category D Resources speculative and completely uneconomic + Camisani-Calzolari (1984) ++ Calculated after data by Crocker (1985) and pe.-s. comm.; and by Andersen & Roets (1983) TABLE 5 K-, fa RICH GRAHITOIDS OF S AUSTRALIA 1 2 3 4 5 6 7 8 9 10 11 12 sio2 69,6 76,3 73,9 72,1 72,0 73,7 70,0 77,0 72,3 65,6 73,8 71,6 Ti02 ,7 ,1 »1 ,1 ,1 .4 ,6 ,1 ,4 ,2 ,2 ,4 A1 14,8 12,2 13,8 15,1 12,9 14,2 13,5 12,6 14,6 16,1 14,7 17,7 2°3 Fe203 »8 .2 ,6 ,5 1,0 1, 4,4 ,3 1,2 2,1 - - FeO 3, ,9 1.1 .2 2, .6 3,1 1,0 ,2 1,4 ,5+ 1,0+ NnO t - t - t ,1 - ,1 ,1 ,1 - t NgO 1.2 .3 .2 .1 1.1 ,3 ,2 ,5 ,3 1, ,5 - CaO 2,0 ,5 ,4 ,6 ,5 t 1,8 ,8 ,3 2,1 1,2 ,4 Ha20 2,6 2,5 3,3 .1 2,8 3, 1,2 1,8 4,4 5,1 6,4 7,5 K20 4,5 5,8 6, 11.1 7,2 6,3 4,7 4,6 6,0 5,1 1,8 ,8 P - .6 t ,3 t 2°5 .1 .2 ,1 ,2 ,1 ,1 ,2 L.O.I.+ .5 .6 .6 t ,6 ,2 ,1 ,5 ,2 ,7 ,4 ,6 Total 99,8 99,4 100,2 100,5 100,3 100, 99,7 99,4 100, 99,8 99,7 100, K20/Na20 1.7 2,3 1.8 111, 2,6 2,1 3,9 2,5 1.4 1, ,3 ,1 K20 + Na20 7,1 8,3 9,3 11,2 10, 9,3 5,9 6,4 10,4 10,2 8,2 8,3 •so FeO/Fe 0 3,7 4,5 1,8 ,4 2, ,6 ,7 3, ,2 ,7 Fe 0_ + FeO 3,8 1.1 1.7 .7 3, 1,6 7,5 1,3 1,4 3,5 ,5 1,0 i ho L.O.I.: loss on ignition PER-158- 13 - TABLE 5 (C05T1RUKI)) BHCOOITER BAT Average of 4 analyses (no. 44, p.38; 5, p.51: adanellite porphyry; 6, p.54: adomellite porphyry; 20, p.56: porphyritic granite) quoted by Joplin (1963). EHCOUHTER BAT Aver, of 3 analys. (no. 20, p.15; 22, p.15; 45, p.17; IMd.). EYRE PEKTHSULA Aver, of 3 analys. (no. 42, p.17; 96, p.23; 3, p.325: granite ortogneiss; IMd.). 4 Ht. PAIKTER AEEA Potash leucogranite (no. 106, p.24, ibid.). 5 Mt. PAIKTER AREA Granite 41 km NE of Ht Painter (no. 112, p.25; ibid.). MIDDLEBACK RAMGE Average of 2 analyses (no. 66, p.20: tourmaline gr.; 91, p.23: pegmatitic gr.; IMd.). EVERASD RAHGE (no. 14, p.14; (iMd..). 8 MIH1IIPPA HILL (no. 104, p.24; IMd..). PORT AUGUSTA (41 km N of Port Augusta; no. 51, p.59; iMá). 10 CROCKER'S WELL Average of 12 analyses of Na-alaskite and trondhjemite (after Ashley, 1984). 11 RADIUM HILL Albite granite ( Mawson, 1944), TABLE 6 K-RICH RHYOLITKS (1-3) AND GRANITOIDS (4-8) OF THE BUSHVELD COMPLEX 12 3 4 5 6 7 8 74,4 74,8 sio2 68,4 71,6 72,6 76,5 75,1 74,5 T102 ,5 ,3 ,3 ,1 ,2 ,1 ,3 11,5 11,6 11,8 12,1 11,3 13, 12, 12, A12°3 Fe - - 2,5 ,7 2,4+ ,6 1,8 2°3 1, FeO 6,5* 6,3 2,3 2,1 - 1. ,8 1,6 NnO .1 ,1 .1 t t t ,1 ,1 MgO ,4 ,2 ,2 ,1 t ,3 ,1 ,1 CaO 2,4 ,6 1,1 »8 ,5 ,8 1,5 ,4 ».2o 1.7 2,2 2,8 3,2 3,2 3,4 2,3 3>1 K2° 4,3 4,9 5,0 5, 5, 5,1 4,7 5,2 P t t t t t t 2°5 ,1 .1 L.O.I,** 3,1 - ,7 ,5 - ,5 ,9 ,5 Total 99, 97,9 99,4 99,1 99, 99,7 98,6 99,6 K20/Na20 2,5 2,2 1,8 1,6 1,6 1,5 2,0 1,7 K20 + N*20 6,0 7,1 7,8 8,2 8,2 8,5 7,0 8,3 ^ FeO/Fe203 - - ,9 3, 1,7 ,8 ,9 ? Fe + Fe0 6,S 6 3 4 8 2 8 2,4 1,6 1,8 3,4 » 2°3 ' » ' 4?- ** Lost on Ignition I * Total Fe as FeO + Total Fe as Fe 0 PER-158- 15 - TABLE 6 (COHTIHOED) 1 Eooiberg felsite, mean of 131 low-Mg lavas from the Loskop Dam area (Twist, 1985). 2 Sooiberg felsite, mean of 32 analyses from the Rust de Winter area (De Bruyn, 1980). 3 Rooiberg felsite, mean of 3 analyses (listed in Tankard et al.r 1982, p.193). 4 Nebo granite, mean of 37 analyses (ibid.). 5 Nebo granite, average composition of the top of the intrusive sheet (MacCaskie, 1983). 6 Nakhutso granite, mean of 20 analyses (listed in Tankard et al.. op.cjt.). 7 Bobbejaankop granite, mean of 6 analyses (ibid.). 8 Granophyre, mean of 5 analyses (ibid.). PER-158- 16 - The first argument against metallogenic equivalence is the paucity of appreciable tin concentrations in South Australia and adjacent regions (Johnson & Gov, 1975) relative to the Bushveld. This is a remarkable fact if the stability of cassiterite to weathering processes is considered. If we then analyse the lithogeocheaical evidence, Tables 5 and 6 indicate that there are also significant differences in the composition of the Pre-Adelaidean granitoids relative to those of the Bushveld. The former appear on average more potassic (or exceptionally sodic), and with higher total iron and total alkali contents than the Bushveld granites. This in turn suggests that the former experienced a history of more protracted fractional crystallization, or a derivation from LILE-enriched, metallogenically more specialized parent melts. The alleged similarities of SEE patterns between the granitic rocks of the Olympic Dam deposit and those of the Bushveld Complex were also considered by Twist (1986) to be an element in support of the model he proposed. However, REE patterns showing a relative enrichment in LREE (light REE), a negative Europium anomaly and a somehow flat HREE trend are not specific to the Olympic Dam, to the Bushveld granites or even to the granites with a metallogenic specialization. Rather, these patterns are the norm in fractionated granitic rocks, and examples of similar patterns are seen in: Isle of Skye, R W Scotland Thorpe et al.. 1977 Namaqualand granite gneiss McCarthy & Kable, 1978 Composite of ± 400 granites, USA Koljonen & Rosenberg, 1974 Outer granite gneiss, Vredefort Hart, unpublish. data As a consequence of this, we do not think that the REE patterns of the Bushveld granite may be used to draw ccr elusions for an Olympic Dam equivalent. PER-158- 17 - Until proved otherwise it is possible to speculate that the magnetic anomaly deep below the Olympic Dam deposit is caused by a davidite-rich mineralized body like those of the Willyama Inlier (nos. 7-10, Table 1). A calculation of the total uranium present within the Vergenoeg pipe (Table 7), finally indicates that this volcanic structure contains ca. 8 x 10 t U at an average grade of ca. 50 ppm. Reserves at Olympic Dam, calculated at an average grade of ca. 800 ppm, are fit least 1,0 x 10 , or more than two orders of magnitude higher. One is left to wonder what the total reserves would ue if an average grade of 50 ppm was also used to calculate the U present in situ in the Olympic Dam graben! If we consider the metallogenic history of the mid-Proterozoic inliers of South Australia - I«ew South Wales we see features which are missing in the Kaapvaal Craton: (a) The regional extent that U, REE-titanates-, sulphides-, oxides-rich sodic anatexites and gneisses have in the Willyama inlier (Ashley, 1984) (b) The reported presence of P, K, Hi, Co, U, REE, Au-enriched basalts and norites in the Stuart shelf and elsewhere in South Australia (K. Maiden, 1984, pers. comm.; Joplin, 1963, p.22, no. 1), the geochemical signatures of which rather suggests a kinship to the 1,1 Ga old Fe-Cu-Th-U-REE ± Ni mineralized KREEP norite suite of Ramaqualand (Andreoli et al.. 1986) (c) The presence in the Willyama complex of the mid-Proterozoic Broken Hill deposit, which is a LILE-enriched Pb, Zn, Ag base metal deposit of world class and which has recently been reinterpreted as the product of mantle metasomatism in a giflfceji (compare this with Olympic Dam) environment (Plimer, 1985) (d) The close proximity of the Olympic Dam and associated deposits to the Torrens fault or hinge zone and to the western margin of PER-158- 18 - TABLE 7 CALCULATION OF D,0 BESEKVES IH THE VEKGEHOEG PIPE* CAP (GOSSANOUS) d diameter (m) 800 h height (m) 40 s shape cylindrical D ore density (t/m ) 3.3** g grade UO (average, (g/t) 20 • Jo g grade UJ3fi before leaching (g/t) .. 50 PIPE d diameter (m) , 500 H1 height (m) 600 s shape inverted cone 1 3 D ore density (t/m ) 3.5 g average grade U.O (g/t) 50 U30g IN CAP (GOSSANOUS) 1) present day: (-) hDg « i 330 t 2) at emplacement: ... (*) hD g * 3 520 t U30g IN PIPE 3) at present: (^)2 ^D1g1 s 6 870 t TOTAL at present (1 + 3) = 8 200 t at emplacement (2 + 3) • 10 440 t leached out (2 - 1) = 2 240 t * Based on data by I. Crocker (pers. comm.), Crocker (1985), Andersen & Roets (1983). **assumed PER-158- 19 - the Adelaidean metallogenic province - the Torrens hinge zone is an important structural discontinuity which separates the undisturbed Stuart shelf on the west from a highly deformed late Proterozoic, diapirs-rich domain in the east The possibility that the Bushveld Complex evolved from a major astrobleme at ca. 2,1 Ma ago (Elston & Twist, 1986) is a final argument that may restrict a comparison between the mineral potential of Olympic Dam and that of the Bushveld Complex. In conclusion, the authors believe that a strict comparison between the Bushveld and the Stuart Shelf metallogenic provinces is not justified, and that the potential to find an Olympic Dam-type uranium deposit in the central-northern Transvaal is rather small. 3 THE WATERBERG COVER: A TARGET FOR UHCOMFORMITY-TYPE DEPOSITS? Despite more than a decade of extensive investigations in many parts of the world, only two uncomformities have been found to host and control viable uranium deposits, namely those in N Saskatchewan (Canada) and in the Australian Northern Territory (E. Cheney, pers. comm.). This intriguing aspect of the rarity of the uncomformity-type mineralization is even more acute if we consider the recent attribution of the Australian Kombolgie deposits (e.g. Ranger, Jabiluka, E. Alligator R.) to the class of vein-like mineralizations (F.J. Dahlkamp, pers. comm.). In this case the only example of uncomformity-related deposits remains that of the <1,35 6a Athabaska uranium province. It is important to explain this fact or at least to limit its possible causes if we want to evaluate the exploration potential of the uncomformity at the base of the Waterberg. Recent literature data on the genetic aspects of the Athabaska and Kombolgie uranium provinces appear to preclude any simple model. Consequently, we PER-158- 20 - think that the expectation to identify uncomformity-type targets in central-northern Transvaal is over-optimistic because: (i) The Canadian and Australian deposits present uncertainties (Lainé, 1985, Anonymous, 1986) in relation to: (a) Source of U and its transporting solutions (b) Lithological and structural controls (c) Origin and role of organic matter reductants (d) Isotopic age differences between younger U mineralizations and older alteration halos (ii) Absence of an obvious time-bound relationship for the mineralization processes which took place over a long period of time, (Table 8) after the atmosphere had acquired its oxidizing chemistry at ca. 1,9 6a ago (Toens, 1981) (iii) Substantial differences between the geological history of the Waterberg basin in Central/Northern Transvaal and that of the Athabaska/Kombolgie basins, which two uranium provinces have, in contrast several features in common (Table 8, Kirchner e_t a_l., 1980) (iv) Harked lithological differences between N Saskatchewan - N Territory and the Transvaal (Table 9), and especially the scarce development of carbonaceous organic material in the Waterberg or in older Kaapvaal rocks (with the exception of the kerogene-bearing Witwatersrand quartz-pebble conglomerates) Referring to point 1 above, we note that there are uncertainties also as regards the origin of other elements accompanying uranium, such as Ni (and Co, Cu, Pb, Zn) in the case of Key Lake (Strnad, 1983) or Zn, Cu, Ni, Co, P, Y, REE at Jabiluka (Gustafson & Curtis, PM-158- 21 - TABU 8 COHPATAXIVI «OCHEOWLOCT OF DBCOWfOmiTÏ-gELATED 1 SASKATCHEWAN 2 TRANSVAAL (S.A) 3. NORTHERN TERRITORY .',: .17 - .«2 Ori «KM. MP»»!**. £ UraiMHtt. Chlartte frt» itftral v- Otpwlffl ï: 0.M-».*» IKH U »«wHli«itipn"" 0 1.01 UraniMit. Pua jwifV" 17 - 1.J5 Aft rpngr far wnc9nf#ra»ty I I - 1.3 Uranautt. JttnuHa' rtlltio •rti11' !•»(?>.t AtllpPMka '• 1.3-1.4 'iwmitrj AIMW» c«vmnl U-Ni ffinprplitptipn. Kff1r LMt^l — 1.SS:0.1 *J-Rte HintrplilptMft, Hprp — I.SI u »tt «Kiefattia'nW. «Nllfnaa í •)•«!" S Am NJ •»!•• ! l Sl-vr 0lrapic 0M Nwi'/'sfai ! •-* It Cmar.fiM' )•»•!>**. IMHrl»»''5! ,J" «..».10« f,"' U7l0.03 NtMlatM 6f•».!•'" Urpnmitt PanfP*'*' t*ft af AtMPPMP »•'" ./.•1.0Í-I.1 t-I.AÏ «I IM ««Itrpl 171 OnatnflKlí ItM H «WfPPfP, San II I» ; 1.73-1.71 u RICH Grawnn. hut Crtt» f 1,71« O.M PitcMWMt V»«ll, G.o.1'0) UfMDM Citf Afpt141 i. "L, IrHO Mill HiMral„!•!! '«HAM. S ; 1.» Uranimtp. Ttfpplt Prpap. Pint i 2 m I.HfMt Urpmmtt, UTMIU* »*>i CrtM Gnf' ' 7.9 s 0,03 StpnrM erpmpiiiff»"1 U Run twparpltt1*1 >»- — J.OItOíJ «tpatramta,H1 I >• «WW03 Miaitktot Cp»pi«>'" l.t-l.l Paw Crtft Oppf'" Tj.PSt0.02 «.ittMurp. Hr tui«f'i> JP lapprtpnt u •nriinmtni in MMI *»»• M.fll pita CM*r ttucxtK rt radii mttrprptao' Í>-J7 úrpmfi lnw'»IIOpp* Ul •I «tff >»•»€« Hpft «HPIt» IHH'Wtl U «Hltfahlalit""1 l!< «rcMM.i ••••••nf'" PER-158- 22 - TABU 8 (COHTIBUED) 1. Bell, 1985 2. Wendt et al.t 1978 3. Lainé, 1985 (1) 4. Trocki et al.r 1984 5. Koeppel, 1968 6. Parslow & Thomas, 1982 7. Kirchner et aj..f 1980 1. Lurie, 1986 2. Cheney & Twist, 1986 3. Coertze et a}., 1978 (2) 4. Von Groenewaldt et al.f 1985 5. Erikkson, 1984 6. H. Allsopp, pers. comm. 1. Page et a!.. 1980 2. Heedham et aj.r 1986 3. Page, 1983 4. See Table 1 (3) 5. Gustafson & Curtis, 1983 6. Hills & Richards, 1982 7. Derrick, 1982 8. Ferguson et al.. 1980 9. Laing et al.f 1978 10. Crick & Muir, 1980 TAJM.1 a coNMMtrn onuocT or «KOMromiTt-nra otPosiTa AID cnmuu. • TMMVAJU. MUDiac ntr uurt* JABILUKA* BUSKVKLD COMPLn AMU om RRUkTioasHips In tha footwall and completely A* Key lake, ditto Insignificant u anomalies In tha upper To aid-Protero»lc covered during ore forming «went parts of tha conglomerate overlying the uncomforalty Waterbnrg/nushveld Complex unconformity STRUCTURAL COWTROL Faulting. Pre- and post sandstone Collapse breccias Post deposition»! faulting; tectonic silvers of granite In lower Watarberg normal, vmn O.M Ga; diabase dykes 0.9* - 1,23 > 0.» ~ 0,9 epeircgenlc activity MOST HOC* of U Lower ffoteroiolc graphite cordlerlte Lower Proterotolc graphite Carbonaceous/graphite bearing rocks pre concentration; gneiss; 2-10 ppm but up to 300 ppsi in dolomite quartz-chlorlte- generally missing in Transvaal sequence U ppsi places feldsrur schists; 9-13 ppm imTJMOKrMlSH OP MOST ROCK Prograde and regional to upper Prograde and regional to Only contact metamorphlsm caused by amphlbollte fades 1,8 Ga ago. Possible amphlbollte facias 1,8 Ga Bushvald Complex retrograde metamorphlsm ago. Retrogression to greenschists facias ca. 1,6 1,7 Ga ago ARCHAEAN BASKMRMT Mejuvenation at 1,9 Ga. Anatectic Rejuvenation 1,8 Ga ago Archaen granite gneiss > 7,6 Ga -d pegmatotds in Wo11aston apllte produces mlgmatltea near with very rare and minor U 50 I << 18 ppm U) contact with L Proteroiolc ~* cover <- 10 ppm U) mineralizations (loc. no 5, fig. ?) C» I • After Klrchner at at.. 1480 PER-158- 24 - 1983). In the case of Key Lake the abundance of Hi is perhaps as surprising - and unexplained - as that of chromium in the U-REE mineralized felsic gneisses of Radium Hill (no. 9, Table 1). The authors believe that the genesis of the Athabaska and Kombolgie metallogenic provinces resulted from the unusual combination of several events, each holding the potential for a step-wise increase in U concentration. These events are listed as follows, the oldest process being at the bottom (i): (v) Basin dewatering, migration of connate waters; heating events of regional character promoting brines circulation, elemental solution/precipitation (iv) Deposition of a regionally extensive sandstone following deep erosion of the metamorphic basement down to the level of the (U-bearing) amphibolite facies (iii) Medium-grade metamorphism (~ 1,8 6a old) accompanied or followed by the emplacement of U-enriched granite (Australia) or high-grade hydrothermal U ores (Beaverlodge and Gunnar deposits; Dahlkamp, 1979) (ii) Erosion of Archaean basement and deposition (> 2,0 6a) of U-enriched carbonaceous shales/evaporates (i) Moderately enriched Archaean basement granitoids There are also some puzzling features in the geology of the Athabaska and Kombolgie deposits that suggest the influence of more exotic metailogenic models, such as coupled crust-mantle uranium fertilization. These features are: (5) The presence of U-enriched mafic pegmatoids in the (Aphebian) metamorphic sequence below the Athabaska uncomforaiity. Such rocks resemble the REE-U mineralized MASAD suite described by PER-158- 25 - Andreoli and Hart (1985) and Andreoli (198A) from the type area near Hsanje and Tete (Mozambique-Malawi border). Furthermore, like Tete, the Gunnar uranium deposit is also in albitized igneous rocks. (6) The coincidence of the main event of metasomatism and mineralization (?) at Jabiluka and Nabarlek with a relatively short period of time (ca. 0,3 Ga) during which most of the pre-Mesozoic U and base metals (except Ni) endowments of Australia were established (7) The intrusion (ca. 1,75 Ga ago) within the Pine Creek geosyncline of a very large granitic massif (500 x 250 km) which contains up to 20 ppm U. Commenting on the apparent relationship between uranium mineralization, U-enriched granitic rocks and rifting, Rossiter & Ferguson (1980) have suggested that U had been introduced into the crust by hot, LILE-enriched mantle plumes. At variance with the Bushveld granites those of Australia do not seem to form a bimodal suite with mafic plutonic rocks. We conclude that there are substantial differences in the geological evolution of the Kaapvaal Craton as compared with the Slave province of Canada and the Pine Creek geosyncline domain of Australia which make the presence of giant uranium ore bodies in the Kaapvaal only a tenuous possibility. 4 ADDITIONAL TARGETS FOR DRAHIOH EXPLORATION Rashoop Granophyre Suite. Acidic rocks of granophyric aspect constitute a significant proportion of the Bushveld Complex and therefore they may be considered as additional targets for U exploration (Cheney, 1986). According to this author the economic potential of the granophyres is directly related to an anatectic/migmatitic origin of these rocks PER-158- 26 - either fro» a felsite or fro» • sedimentary precursor. As a prominent example of an anatectic/migmatitic deposit Cheney mentions Bossing. A recently published article by Walraven (1985) appears tc reduce the possibility of a granophyre-related D deposit in the Bushreld. According to the Walraven (op. cit.) only the Diepkloof granophyre respresents the product of partial melting of acid volcanics. Unfortunately, this type of granophyre is restricted to the eastern part of the Bushveld Complex and its geochemistry shows LILE (T, Hb and Zr) content lower than that of other granophyres of met amorphic or hyp&byssal origin. The less differentiated geochemistry is consistent with the Diepkloof granophyre, being gradational to granodiorite, a rather primitive type of granitic rocks generally devoid of U mineralizations. Walraven (OP.cit.) also discussed the origin of granophyre-like rocks deriving from high-grade metamorphism of Pretoria group sediments, which he refers to as Zwartbank pseudogranophyre. Geochemical data of the Zwartbank pseudogranophyre indicate a large degree of heterogeneity, a fact in opposition to the needs for fairly constant U grades > 250 ppm. The Stavoren granophyre is the third type recognized by Walraven (op. cit.) who relates its origin to an hypabyssal emplacement of the Rooiberg acid lavas. We will finally recall that the estimated U content of the Rashoop granophyres considered by Simpson & Hurley (1986) is unlikely to exceed 5 ppm. The above data are strikingly at variance with available information on the origin of Rossing alaskite. The latter is a K-rich pegmatitic granite, possibly derived from the melting of uraniferous, high heat production (anatectic) granites emplaced during earlier phases of the high-temperature Damara Orogen (Brynard & Andreoli, 1985). PER-158- 27 - We believe that the aetallogenic specialization of the Bossing alaskites is related to the broader framework of U-enriched •etasoaatisa and aagmatisa in the Pan African doaains of Central Africa (Zaabia, Zaire : G. Martinotti, pers. comm.) and Southern Africa (Brynard and Andreoli, 1985; Andreoli, 198A; Andreoli & Hart, 1986; A. Schoch, pers. conn.). Our conclusion is therefore that there is no likelihood of a Rossing-type uranium deposit in the Bushveld nor is there a high-priority target vhich could be easily designated in the granophyres. Hydrothermal vein-type U deposits, like that of Albert Silver mine, are reasonable exploration targets according to Cheney (1986) and Simpson & Hurley (1986). In the latter work emphasis is placed upon the spatial relationship between known U anomalies and two sets of near-orthogonal tectonic trends. These were first described by Wilson (1979) as linear zones of (tin-) fluorine enrichment of the Kaapvaal craton. One of these, the Murchison Range lineament, also hosts the U-F enriched Pilanesberg Alkaline Complex and the Groothoek-Doornrivier U prospect (Zebediela, Pietersburg). These observations would provide an important tool in the screening of hidden vein/pipe related U mineralizations. A note of caution should however be sounded since Lee and Sharpe (1986) found no evidence for the concept that deep-seated crustal fractures influenced the location and form of the Complex. In view of the broad geochemical affinity of uranium and tin, it is interesting to consider the tin prospecting targets in the Bushveld Complex given by Crocker & Callaghan (1979). These authors, however, found no guideline in the exploration of hidden lode, fissure-type tin deposits in granite and granophyre. 5 DISCUSSIOH k BECOMHEHDATIOHS In this investigation we have considered the potential of the Bushveld Complex as a host of giant uranium deposits of the types found (a) at Olympic Dam, (b) below the uncomformities of N PER-158- 28 - Saskatchewan (Canada) and the II territory (Australia); and (c) in the central Damara orogenic zone of South-West Africa. From a careful examination of the available evidence ve came to conclude that the tectono-metamorphic and metallogenic history of the Bushveld Complex substantially differs from that of the U districts listed above. As a consequence there is little support for models which support the presence of Olympic Dam, uncomformity or Rossing-type deposits. On the contrary, there is a reasonable potential for - (a) volcanogenic deposits, especially in the Rooiberg felsites; (b) Vergenoeg-type residual magmatic systems; and (c) hydrothermal, vein/stockwork type deposits (Albert Silver Mine, Groothoek-Doornrivier). For target a) there is the important provision that a leaching episode, as suggested by D Twist (pers. comm.), must be demonstrated before initiating the search for suitable final depositories. Search for a Phalaborwa-type deposit should and must not be restricted to the Bushveld Complex or adjacent domains since carbonatites may intrude the southern African (Precambrian) craton in many different environments. The Chilwa alkaline province (Malawi), the Haponde Complex (Mozambique) and Zandkopsdrift (NW Cape, S. Africa) all pierce late Proterozoic mobile belts. Data for the Bushveld Complex rocks indicate that in the high-cost reserve categories the grades may be very low (Vergenoeg) and that in the low-cost categories the tonnages are insignificant (Albert Silver). We conclude that our current and long term scientific research must locate not only additional Vergenoeg/Albert Silver type deposits, but also ore bodies with substantially enriched grades and/or tonnages. PER-158- 29 - The possibility of finding ore bodies with enrichments up to a factor of 10 times those which are presently known should be considered very optimistic and speculative but not altogether unrealistic on the basis of current .geological knowledge. On the contrary, it is less likely that a fluorspar pipe- or vein-type deposit may be found with enrichments of reserves and/or grades by factors significantly greater than 10 times. The potential for volcanogenic, caldera-type ores and for viable Groothoek-Doornriver type uranium deposits remains to be demonstrated. The current resea-^n sponsor'< at the Bushveld Research Institute by the AEC should, i*: our opinion, concentrate on one or more of the following topics: (i) Ground control and lithological characterization of most, if not all, airborne radiometric anomalies as they are defined by the new computation of the Geological Survey flights data (ii) Screening of all aeromagnetic anomalies in the Bushveld Complex that are comparable in size/intensity to that of the Phalaborwa and Vergenoeg pipes (iii) Geochemical, mineralogical and isotopic characterization of the Rooiberg felsites to define mineralogical siting of uranium, leaching events and their timing (iv) Age determination of Vergenoeg-type U anomalies to confirm their origin from residual melts of the Lebowa Granite Suite as proposed by current models (v) Clear answers to the problem of the origin of the felsite* and indication of suitable structures, such as calderas, that may act as traps to U-enriched late volcanic fluids PER-158- 30 - In the final presentation of the research results to the AEC, the existing structural aap of the Bushveld could provide an useful format to outline target areas for future research and prospecting. 6 ACOOHLKDGEHEHrS We thank Dr P D Toens, Mr P J van der Nerve (AEC) and Dr D Twist and J Schweitzer (U P) for the useful data and comments provided. We are indebted also to I Crocker, C Callaghan and F Wal raven for guiding very interesting field trips to the Bushveld Complex, to Hiss E E Groenewald for patiently typing the manuscript, and to the staff of the drawing office (AEC) for their draughting ability. 7 KEFKEHCES ANDERSEN, N.J.B. & ROETS, D.L., 1983. Report on the radiometric borehole logging conducted by NUCOR VG 6 on the Vergenoeg Fluorspar mine. Pelindaba report PIN-682(B/R), GEA 414, 6 pp. ANDREOLI, H.A.G., 1984. Petrochemistry, tectonic evolution and metasomatic mineralization of Mozambique Belt Granulites from Southern Malawi and Tete (Mozambique). Precambrian Res., v. 25, p. 161-186. ANDREOLI, M.A.G. & HART, R.J., 1986. Evidence for Proterozoic LILE-fertilisation of the lithosphere, part I: metasomatised granulites of the Mozambique Belt. Geol. Soc. Australia Special Publ., in press. ANDREOLI, M.A.G., ANDERSEN, N.J.B. & FAURIE, J.N., 1986. 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