Abstract:

The crystalline rocks represent the most weathering rock groups due to their textural and mineralogical decomposition. This study, focused on the petrographic properties and geochemical variation of the altered rocks from Demirköy Intrusive Body (DIB) located at NW Turkey were examined based on the location of structural and morphological properties. DIB consists of intrusive rocks in the composition of ranging from granite to gabbro. The sampling made from the dominant rock units composing of granodiorite and quartz diorite, within the DIB a cross weathering section divided into three levels as regolit, saprolite and saprock. For each level of all the section Ruxton ratio (Ro), chemical alteration index (CIA), chemical weathering index (CIW), plagioclase alteration index (PIA) were determined. The results show a linear decrease from the surface to the core of the host rock. The chlorite-carbonate-pyrite index (CCPI) versus Ishikawa alteration index (AI) variation diagram shows that decomposition in profiles occurred in diagenetic alteration and where the hydrothermal alteration effect is not observed. On the other hand, Mg, Fe, Ti, Ca decreased remarkably while the ratio of the elements such as Si, Na, K, Al increased. The increasing and decreasing of geochemical elements are related to their physical strength and chemical behavior. The chemical variation diagrams of all the levels revealed that the regolites exhibit chemical compounds from hydrothermal fluids in the immediate vicinity of the source rocks.

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