石油实验地质2016，Vol.38Issue(6)：772-778,7.DOI:10.11781/sysydz201606772
羌塘盆地南部布曲组含油白云岩中自生文石胶结物的鉴定及其成因探讨
Mineral and genesis study of authigenic aragonite in sucrosic dolomites from Middle Jurassic Buqu Formation in southern Qiangtang Basin, Tibet
摘要
Abstract
Columnar⁃acicular cement has been discovered in the Middle Jurassic Buqu Formation of Longeni area in the southern Qiangtang Basin of Tibet, distributed in saccharoidal dolomite in dissolution pores filled with bitumen. As demonstrated by microstructure, in situ X⁃ray diffraction (XRD) and electron microprobe analysis (EMPA), minera⁃logical investigations have confirmed the emergence of authigenic aragonite. It occurs as bundles and radiating clusters consisting of needle crystals. Major elements show that MgO and SrO have a positive correlation. In situ isotopic analy⁃sis indicates thatδ13 C values range from 3.5‰PDB to 3.98‰PDB andδ18 O ranges from-9.98‰PDB to-11.63‰PDB. Aragonite is rarely found in carbonate rocks formed during geological times because of the conversion of aragonite to low⁃Mg⁃calcite through neomorphism or dissolution. Oxygen and carbon isotopic composition of aragonite cements in saccharoidal dolomite has greater variability compared with aragonite formed in modern marine or meteoric diagenesis. In the formation process meteoric water leaching has less influence and a negative excursion of δ18 O is mainly con⁃trolled by geothermal gradient during burial. The reservoir diagenetic sequence shows that aragonite cements formed af⁃ter burial dolomitization. Authigenic mineral precipitates with organic acid dissolution, and hydrocarbon filling has largely inhibited the conversion of aragonite to calcite. The comprehensive analysis suggests that aragonite cements were precipitated from a dissolution-reprecipitation process of carbonate minerals during late diagenesis. Hydrocarbon filling played an important role controlling the preservation of aragonite cements.关键词
文石/微区X射线衍射/碳氧同位素/中侏罗统/羌塘盆地Key words
aragonite/micro X-ray diffraction/carbon and oxygen isotopes/Middle Jurassic/Qiangtang Basin分类
能源科技引用本文复制引用
张帅,伊海生,夏国清,梁定勇..羌塘盆地南部布曲组含油白云岩中自生文石胶结物的鉴定及其成因探讨[J].石油实验地质,2016,38(6):772-778,7.基金项目
国家自然科学基金（41572089）和国土资源部沉积盆地与油气资源重点实验室开放基金（zdsys2014002）资助。 （）
