The Mineralizations, associated with basic and ultrabasic rocks of İslamköy (Diyarbakır)

IV ABSTRACT (Ph. D. Thesis) THE MINERALIZATIONS ASSOCIATED WITH BASIC AND ULTRABASİC ROCKS OF ISLAMKÖY ( DİYARBAKIR - KULP ) Muharrem AKGÜL Fırat University Gradute Scholl of Science and Technology Department of Geological Engineering 1993, Pege: 116 The studied area, Islamköy Region, is situated in 15 km.s ( approx.) NW of Kulp township of Diyarbakır. Three different stratgraphic units are present in the studied area; Paleozoic Bitlis Metamorphics, Jurassic - Cretaceous Kulp Ophiolite and Lower Miocene Lice Formation. The studied area is situated on the South East Thrust Zone and the units exhebit tectonic contacts. In Islamköy region two different aged thrust zones are exist; the older one is of post Cretaceous the younger one is post Lower Miocene. In the region a rifting had begun during Triassic, the Kulp Ophiolite had formed during Jurassic - Lower Cretaceous and the ophiolitic rocks hed been thrusted over crust during Upper Cretaceous.During Lower Miocene, as a consequence of Arabian Plate - Anatolian Plate Collision, the rocks were thrusted from North to South and over Lice Formation. In the studied area, gneiss, quartz - mica schist, granat - mica schist, amphibole schist and merble of Bitlis Metamorphics are present. The schistosities of there are rocks are distinct and dip towards North. The Kulp Ophiolitic rocks are composed of Iherzolite, harzburgite, dunite, websterite, gabbro.diorite, diabase and volcanic rocks and appear as highly altered and fractured. The Iherzolitic, harzburgitic and dunttic rocks form lower parts of the ophiolitic sequence and are equivalents of tectonics. Theserocks exhibit porphyrclastic textures. Websterite, gabbro, diorite and quartz diorite are the cumulatte rocks of the ophiolitic sequence and these rocks show mesokumulate and subhedral granular textures. The diabasees belong to sheeted dyke complex and have intergranular and intersertal textures.The basaltic volcanics from uppermost parts of the ophiolitic sequence and have microporphric and vrtroporphric textures. The analysis of the Kulp Ophiolite show that Si02, Al203, CaO, Na20, K20, Ti02 and P205 values increase from peridotitle towords basaltic rocks and a decrease in MgO and volalites contents. The trace elements; Sc, Sr, Zr, Ba, Ce, Nd and Y increase in the same older and Ni, Cr decrease. These changes are due to magmatic fractionation and these analysis values indicate a middle oceanic ridre origin. Lice Formation is consist of sandstone, shale and marl alternations in teh studied are and these rocks show thin bedding. The mineralizations associated with Islamköy basic and ultrabasic rocks appear in there types. These are; chromite, sulphide and thrust zone mineralizations. The chromite mineralizations are situated in the northern slopes of Ganzik Tepe ( Hill). The mineralizations are within dunitic rocks and appear as a single lens shaped body. The microscopic study reveals that the mineral assemblage of the chromite mineralizatians is chromite, pentlandite, millerite, heazlavodite, ilmenite and rutile. Chromite grains are subjected to tectonic strains and are fractured and broken. Fe mineral exolutions are extensive in the chromite grains. Microscopic works and evaluation of analytical values ( as MgO/ FeO, Cr / Fe and Al203 ) indicate that the chromite mineralizations are of Alpin Type and resulted from fractional crystallization. The sulphide mineralizotions appear as irregular veins within ultrabasic rocks. The dominant ore minerals are chalcopyrlte, pyrite, pyrrhotite, magnetite and sphalerite. In lesser amounts pentlandite, linnaite, chromite and ilmenite are present. Secondary minerals are marcas'rte and limonite. The sulphide mineralizations exebit replacement and exsolution textures extensively. Replacement textures are mostly related to chalcopyrite and in lesser extends to magnetite and pyrrhotite. The sulphide mineralizations show extensive exsolution texteres; chalcopyrite from sphalerite, sphalerite from chalcopyrite, pyrrhotite from sphalerite and pentlandite from pyrrhotite are the most common exsolutions.VI For the formations of the sulphide mineralizotions several probabilities are in vestigated. The probable models are; hydrothermal vein type mineralization, mineralization due to serpantinization and magmatic segregation. The microscopic works and mineral assemblage a high temperature formation. Thus first two models seem not valid. The mineralizations, probably, formed as sulphide phase reacted with then partly crystallized silicate phase. The trust zone mineralizations were formed by hydrothermal solutions what were as a consequence of thrusting of Bitlis Metamorphics on Kulp Ophiolite. KEY WORDS : Basic and ultrabasic rocks, ophiolite, chromite, podiform chromite, replacement, exsolution, Fe-Cu-Ni mineralizations