成都理工大学学报（自然科学版）2018，Vol.45Issue(2)：129-141,13.DOI:10.3969/j.issn.1671-9727.2018.02.01
羌塘盆地南部古油藏带布曲组白云岩地球化学特征及成因机制
The geochemical characteristics and mechanism of dolomite in the paleo-reservoir of Buqu Formation,south Qiangtang Basin, Tibet, China
摘要
Abstract
The observation of drilling cores,study of petrology and analysis of C,O and Sr isotopes reveal that the Jurassic Buqu Formation dolomite in the south Qiangtang Basin consist of original dolomite with original limestone,crystal grain dolomite and dolomite filling.The isotopic value of Sr for dolomite is similar to contemporary seawater and the isotopic value of C and O is positive compared to contemporary limestone.Therefore,the original dolomite with original limestone is formed in evaporative salty seawater with limited environment in penecontemporaneous stage of highstand system tracts.The fast-flowing and highly supersaturated dolomitization fluid is favorable for preservation of original dolomite.For crystal grain dolomite,the value of isotopic Sr for fine grained euhedral dolomite and fine grained semi-euhedral dolomite is the same as contemporary seawater.Compared to contemporary limestone,the value of isotopic C and O are positive and compared to original dolomite with original limestone,the value of isotopic C and O are negative.In shallow burial stage with limited environment in penecontemporaneous stage of highstand system tracts,the crystal grain dolomite is formed by metasomatism from original limestone duo to back-flow or infiltration of evaporative salty seawater.Over-dolomitization is responsible for the formation of fine grain euhedral dolomite.The mid-coarse grained none-euhedral dolomite is formed in mid-deep burial stage,and the value of isotopic Sr is the same as the contemporary seawater.However,the value of isotopic O is negative compared to other dolomites,it may be resulted from recrystallization of early dolomite.It shows that the value of isotopic C in the dolomite is the same as limestone in some of samples duo to incomplete metasomatism,and high diagenetic temperature is responsible for the distortion of crystal surface.The study reveals that the fine-mid grained,euhedral and semi-euhedral dolomite filling are formed in late shallow buried stage to early mid-deep buried stage,as a result of recrystallization.The value of isotopic Sr for saddle shaped dolomite filling is higher than that for contemporary seawater,the distribution scope of isotopic C is wide,and the value of isotopic O is negative compared to midcoarse grained none-euhedral dolomite.These geometrical characteristics are considered to be resulted from atmospheric fresh water infiltration and heating source in 64～78 Ma B.P.,caused by shearing in late early Cretaceous period.关键词
白云石结构/同位素地球化学/白云石化机制/布曲组/羌塘盆地Key words
dolomite texture/isotope geochemistry/dolomitization mechanism/Buqu Formation/Qiangtang Basin分类
天文与地球科学引用本文复制引用
万友利,王剑,付修根,谭富文,王忠伟..羌塘盆地南部古油藏带布曲组白云岩地球化学特征及成因机制[J].成都理工大学学报（自然科学版）,2018,45(2):129-141,13.基金项目
国土资源部基础性公益性油气基础地质调查项目(121201010000161110) （121201010000161110）
中国地质调查局项目(1212011221114) （1212011221114）
国家“十二五”重大科技专项(2011ZX05004-001). （2011ZX05004-001）
