DS9 Document EFTA01168760

Ser 4) association of kyanite, phlogopite, Mg chlorite and quartz with rapeated re- equilibration of kyanite into white mica + Mg-chlorite. 2.3. Core drills Some relevant sections of core drills stored at the Kimale Camp have been examined at the microscope. They offer several continuos sequences of observation on the type of transitional or sharp boundary between basement and cover, including mylonitic type of foliation of the intervening sequence of rocks. In DD 36 core drill, at a depth between 175 and 178 m,a tectonic ty- pe of transition may be seen between basement and cover rocks. Six thin se- ctions have been examined (2M 197 to ZM 202). The original basement granite is composed of quartz, K-Feldspar, plagioclase, muscovite and biotite. Pla- gioclase is transformed into white mica and quartz, biotite is replaced by white mica (phengite) or by a new green-brown metamorphic biotite. Accessory minerals are apatite and opaques. Within 2-3 meters in the core drill sequence this rock is progessi- vely pervaded by an intense mylonitic foliation developing along with a com- plete obliteration of the magmatic mineralogical relics. The mcst pervasively transformed type is a phyllonitic schist, very thinly layered and composed of white mica and quartz in which a porhyrobla- stic kyanite may grow and include the phyllonitic foliation. The same type of tectonic transition is seen in the thin sectioned drill cores made available by AGIP-COGEMA. (drills n. DD 35- OD 37 - DD 12 - DD 13 - DO 10 - 00 17 - DD 8 and DD 3). The drill 00 17 demonstrates moreover that in the Northern border of the Solwezhi Dome the basement gneisses reappear (ZM 216, ZM 217). They contain plagioclase (An< 20%), K feldspar, quartz, biotite and muscovite as main constituents, and epidote, chlorite, sphene, apatite and opaques as ac- cessories; scapolite replaces sometimes the plagioclase. The contact with the overlying Lower Roan metasediments is of tectonic type as demostrated by thin sections of core drills provided by AGIP-COGEMA. In the drill DD 9 at the depth of 148 m an occurrence of a micaceons metabasic rock marks the tectonic contact between basement gneisses and Lo- wen Roan micaschists. This metabasic is two meters thick and is composed of green hornblende and green brown biotite. Its accessory minerals are apatite, calcite, talc and opaques. The fabric is planar and the grain boundary mi- crostructure is rational, with a medium grain Size (ZM 194, ZM 195, ZM 196). EFTA01168760