An Analysis of Ordovician Dolomitisation Origin in Northwestern Tazhong Area

Abstract

Abstract: The study of mineralogical-petrologic and geochemical characteristics of Ordovician dolomite in Wellblock Zhong-1 in northwestern Tazhong area shows that it is composed of dolosiltite, dolomicritein, spotty dolomite, replacement dolomite related with stylolite, baroque dolomite and sugar granular dolomite (dolorudite), characterized by mosaic, mist-core with bright rim, metasomatic and zonal diagenetic textures, reflecting buried diagenetic environment under these different media, with relatively low Sr of 161 ×10^-6, relatively high Na of 0.09%; δ¹³C of -2.0‰ and δ¹⁸O of -6.8‰ in average, which indicate its nature of both buried dolomite and quasicogenetic diagenesis. The fluid inclusion study shows that the buried and dolomitized fluid is bittern with mid-high temperature of 115~130℃ and 170~210℃ and high salinity of 5%~7%, 8%~9% and 12%~13%. It is concluded that such a dolomite belongs to diagenetic dolomite and associated quasi-cogenetic dolomite in supratidal and intertidal zones.

Key words: Tarim basin, dolomite, origin, diagenesis, geochemistry, inclusion

CLC Number:

P595
P642.25

QIAN Yi-xiong, YOU Dong-hua. An Analysis of Ordovician Dolomitisation Origin in Northwestern Tazhong Area[J]. Xinjiang Petroleum Geology, 2006, 27(2): 146-149.

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