Pohl, Walter Dr; Niedermayr, Gerhard; Nauta, W.J. (1979) Kenya-Austria Mineral Exploration Project 1975-1978. Geology of the Mwatate Quadrangle and the vanadium grossularite deposits of the area (with a Geological Map 1:50 000) Report No.101 Vol. 101. Mines and Geological Department, Ministry of Natural Resources 55 pp.
| Reference Type | Report (issue) | ||
|---|---|---|---|
| Title | Kenya-Austria Mineral Exploration Project 1975-1978 | ||
| Report | Geology of the Mwatate Quadrangle and the vanadium grossularite deposits of the area (with a Geological Map 1:50 000) Report No.101 | ||
| Authors | Pohl, Walter Dr | Author | |
| Niedermayr, Gerhard | Author | ||
| Nauta, W.J. | Author | ||
| Year | 1979 | Volume | < 101 > |
| Page(s) | 55 | ||
| Publisher | Mines and Geological Department, Ministry of Natural Resources | Place | Nairobi, Kenya |
| Original Entry | Pohl, W., Niedermayr, G. (1979): Geology of the Mwatate Quadrangle and the vanadium grossularite deposits of the area. Geol. Surv. Kenya, Report No. 101, 55 pp. | ||
| Classification | Not set | LoC | Not set |
| Mindat Ref. ID | 16025708 | Long-form Identifier | mindat:1:5:16025708:9 |
| GUID | 0 | ||
| Full Reference | Pohl, Walter Dr; Niedermayr, Gerhard; Nauta, W.J. (1979) Kenya-Austria Mineral Exploration Project 1975-1978. Geology of the Mwatate Quadrangle and the vanadium grossularite deposits of the area (with a Geological Map 1:50 000) Report No.101 Vol. 101. Mines and Geological Department, Ministry of Natural Resources 55 pp. | ||
| Plain Text | Pohl, Walter Dr; Niedermayr, Gerhard; Nauta, W.J. (1979) Kenya-Austria Mineral Exploration Project 1975-1978. Geology of the Mwatate Quadrangle and the vanadium grossularite deposits of the area (with a Geological Map 1:50 000) Report No.101 Vol. 101. Mines and Geological Department, Ministry of Natural Resources 55 pp. | ||
| In | Link this record to the correct parent record (if possible) | ||
| Abstract/Notes | Within an Austrian Technical Assistance Programme to Kenya, executed by AUSTROMINERAL Ges. m. b. H., Vienna, Austria, between 1975 and 1978, the Mwatate Quadrangle (1:50.000 sheet 195/2) has been geologically mapped at a scale of 1:50.000. The map originally was submitted in AUSTROMINERAL's report,,Geological Prospecting and Economic Assessmentof the Gemstone Belt in Southeastern Kenya" in 1978. Special emphasis was given to the deposits of green vanadium grossularite, which is being exploited as a gemstone and at present constitues the only mineral production of the area. The Mwatate area lies within the Mozambique Orogenic Belt; with the exception of soils and alluvium all rocks encountered are ofPre-cambrian age. They are mainly part of the rock pile generally termed Usagaran Metasediments (HEPWORTH 1971), including metamorphosed pelitic, arenaceous and calcareous sediments with intercalated bands of basic magmatic rocks and some unascertained acidic volcanics. Very small lenses of metamorphosed and highly altered ultramafic rocks occur in the south of the area. A large charnockite complex was mapped in the center of the area. In a wider sense it is thought to represent the basement onto which the sediments were laid down. The rocks are part of the Kurase Series (SAGGERSON 1962), here renamed Kurase Group. The original sedimentary environment was mainly shallow water and marine, with highly variable facies laterally as well as vertically. On this base several lithostratigraphic formations are differentiated. A distinctive rock suite within one of the formations containing the green grossularite deposits is defined as a member. Structures observed point to a threefold deformation: Pre-migmatic isoclinal folds of NNW axial direction are are overprinted by paramigmatic isoclinal or tight folds with northerly plunging axes, and post-migmatic open flexures. Generally, however, the lithostratigraphic suite strikes west of north and dips to the east, except in the northern center of the sheet, where a large monoclinal antiform plunging at a low angle to the north causes a more northerly direction of the dips. The latter is predominant in the Taita Hills immediately north of the present area. The ultramafites are thought to mark a thrust system involving basement (charnockites) and the meta-sedimentary cover. The thrusts were possibly contemporaneous with F1-deformation, and would have been folded and obscured by the later tectonic phases. Metamorphism is of high grade: amphibolite facies and granulite facies mineral assemblages and rock textures have been observed in thin section. Anatectic mobilization of felsic rocks or rock components is wide-spread, and leads to the formation of banded gneisses, migmatites, and anatectic pegmatites. A very pronounced hiatus exists between the granulite facies basement (the charnockites) and the amphibolite facies cover rocks. Five green vanadium grossularite deposits (,,tsavorite") are being exploited at present in the area. These gems have been formed by the concurrence of a combination of suitable material, colouring rare metals, and high grade metamorphism. Other minerals occurring in the area were found to be of less immediate economic potential. Among others they include red corundum (ruby), green tourmaline, blue zoisite (tanzanite), kyanite, magnetite, graphite, marble (limestone), uranium and thorium. | ||
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