川西甘孜-理塘结合带碳酸盐岩碳氧同位素特征  

Carbon and oxygen isotopic analysis of the carbonate rocks in the Garze-Litang suture zone,western Sichuan

作　　者：宁括步 毛世东[2] 梁龙飞 刘伟[1] 马志鑫[1] 罗亮[1] 牛浩斌[1] NING kuo-bu;MAO Shi-dong;LIANG Long-fei;LIU Wei;MA Zhi-xin;LUO liang;NIU Hao-bin(Chengdu Center,China Geological Survey,Chengdu 610081,Sichuan,China;No.12 Geological Party of CAPF,Chengdu 610036,Sichuan,China;Geophysical exploration Party,Hubei Bureau of Geology and Mineral Resources,Wuhan 430056,Hubei,China)

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610081 [2]中国人民武装警察部队黄金第十二支队,四川成都610036 [3]湖北省地质局地球物理勘探大队,湖北武汉430056

出　　处：《沉积与特提斯地质》2018年第3期106-112,共7页Sedimentary Geology and Tethyan Geology

基　　金：中国地质调查项目(编号:DD20160017)资助

摘　　要：本文对甘孜-理塘结合带中段出露的碳酸盐岩进行了详细的野外地质调查,按其产状可分为两类:覆于玄武岩之上的碳酸盐岩构造岩片和包裹于玄武岩内的厘米—米级不规则棱角状碳酸盐岩砾岩块。经碳酸盐岩碳、氧同位素测试分析,前者δ^(13)C值主体位于0. 113‰~1. 625‰之间,δ^(18)O数值为-10. 263‰^-5. 745‰,总体变化较小,有小幅震荡;而后者δ^(13)C值明显较前者大,为4. 254‰~3. 786‰,δ^(18)O数值则明显偏小,为-13. 471‰^-13. 592‰,总体变化量较前者更小,具明显的后期成岩作用改造特征。所有样品Z值均大于123,表明研究区内碳酸盐岩为正常海相碳酸盐岩;结合玄武岩地球化学分析数据认为,碳酸盐岩总体沉积于海山环境,且包裹于其中的碳酸盐岩角砾岩块要早于上覆大套碳酸盐岩形成。The detailed field geological survey and laboratory carbon and oxygen isotope analysis are made for the carbonate rocks developed in the middle part of the Garze-Litang suture zone,western Sichuan.According to the modes of occurrence,two types of carbonate rocks are recognized:carbonate rocks overlain upon the basalts and cm-to m-grade irregular basalt-coated carbonate breccias.The carbon and oxygen isotopic data of the carbonate samples collected from the study area have disclosed that the carbonate rocks overlain upon the basalts display theδ13 C values mostly ranging between 0.113‰and 1.625‰,andδ18 O values ranging between-10.263‰and 5.745‰.However,the basalt-coated carbonate rocks display theδ13 C values ranging between 4.254‰and 3.786‰,which are higher than those of the carbonate rocks overlain upon the basalts,and theδ18 O values ranging between-13.471‰and-13.592‰,which are lower than those of the carbonate rocks overlain upon the basalts.These differences imply that the basalt-coated carbonate rocks once suffered from the paulopost diagenetic reworking.The Z values of more than 123 for all the collected samples indicate that the carbonate rocks in the study area should belong to the normal marine carbonate rocks.It is inferred from the modes of occurrence,lithology and geochemical signatures that the basalt-coated carbonate rocks may be deposited in the seamount sedimentary environments,and their ages are generally earlier than those of the carbonate rocks overlain upon the basalts.

关 键 词：碳、氧同位素 玄武岩 沉积环境 残余海盆 

分 类 号：P588.245[天文地球—岩石学]