DIAGENETIC HISTORY OF THE ROCK UNITS OF BOZKIR UNIT CONTROLLED BY THE TRIASSIC RIFTING, BOZKIR-KONYA

Abstract

The Bozkir Unit representing the northern edge of the Taurus Belt comprises, from bottom to top, three distinct structural entities; the Upper Triassic pre-rift (Korualan Group), the Upper Triassic-Upper Cretaceous syn-rift (Huglu Group) and the Jurassic-Cretaceous Boyali Tepe Group as to their structural settings. The Korualan Group is represented by the alternations of carbonate (limestone, dolomitic limestone, dolomite) with radiolarite and chert intercalations and clastic rocks (sandstone, siltstone, mudstone, shale). The Huglu Group is made up of volcanic (basalt, andesite) and pyroclastic (tuffaceous sandstone) rocks including radiolarite, limestone and clastic rock (sandstone, siltstone, shale) intercalations. The Boyali Tepe Group is completely made of carbonate rocks. The carbonate-silisiclastic-volcanogenic rocks of the Bozkir Unit contain carbonate (calcite, dolomite), quartz, feldspar (plagioclase, anorthoclase), phyllosilicate (illite, chlorite, mixed-layered illite-chlorite / I-C, chlorite-vermiculite / C-V, chlorite-smectite / C-S, rare smectite), augite, hematite, analcime and heulandite in order of abundance. On the basis of illite Kubler Index data; Korualan and Huglu Group reflect low grade diagenetic, high grade diagenetic and high grade diagenetic-anchizonal characteristics, respectively. The illite/micas of the pre-rift units and units related to the rifting have muscovitic, and phengitic and seladonitic compositions, respectively. The distributions of chondrite-normalized trace and rare earth element ( REE ) contents in illites present similar trends for Korualan ve Huglu groups, but the quantities of these elements slightly increase in the Huglu Group. d 18 O–dD isotopic compositions of water forming the illite minerals are different than that of sea water and are found to be between the Eastern Mediterranean Meteoric Water (EMMW) and magmatic water compositions. It also shows that temperature of the water forming illite minerals varies from low to high values. The findings from the rocks of Bozkir Unit suggest that pre- and syn-rift units have different mineralogical-petrographic and geochemical properties. The younger units within the rift due to extension and crustal thinning related to rifting must have been exposed in higher diagenetic conditions by more burial and heat with respect to older units on the edges.