摘要
综合运用岩石学、矿物学和元素地球化学等方法,对柴达木盆地北缘构造带鄂博梁Ⅲ号构造中新统上干柴沟组碎屑岩的成岩作用、形成环境和物质来源等进行了系统研究。发现上干柴沟组碎屑岩中碎屑颗粒间主要以点—线接触关系为主,长粒矿物被定向排列,经历过较强的压实作用。其中黏土矿物含量较高,平均达到了35.03%,主要以伊利石,绿泥石及伊—蒙混层为主。碳酸盐胶结物类型主要以方解石为主,仅含有少量白云石。碳酸盐胶结物的碳氧同位素含量测定表明,碳同位素(δ13C)分布在-6.8‰^-4.0‰之间,平均为-5.0‰;氧同位素(δ18O)分布于-11.1‰^-5.4‰,平均为-8.7‰;根据碳氧同位素含量推算古盐度Z值分布于108.34~114.89,平均值为112.77;碳酸盐沉淀温度分布在43.36℃~77.84℃,平均值为62.30℃。结合对主量元素、微量元素及有机碳含量等地球化学元素的综合分析,认为鄂博梁Ⅲ号构造带中新统上干柴沟组目前所处的成岩阶段主要为早成岩阶段B期至中成岩阶段A期,在形成早期主要以干、冷的淡水—微咸水环境为主,晚期则以要对暖、湿的淡水环境为主。
Based on petrology,mineralogy and geochemistry,the diagenesis,depositional environment and origin of Miocene clastic rock of Shangganchaigou Formation in Eboliang III tectonic belt on the northern margin of the Qaidam basin were studied.The experimental results were that particles of Miocene clastic rock of Shangganchaigou Formation mainly had point contact or line contact relationships,and had been suffered strong compaction;the clastic rock of Shangganchaigou Formation had high contents of clay minerals,whose average value was 35.03%,and which were dominated by illite,chlorite and mixed layer of illite and montmorillonite;the calcite was the main types of carbonate cements,and the dolomite was minor;the carbon isotope(δ13C) of carbonate cements ranged from-6.8‰ to-4.0‰,and the average value was-5.0‰;the oxygen isotope(δ18O) ranged from-11.1‰ to-5.4‰,and the average value was-8.7‰;Z-value of paleosalinity estimated by δ13C and δ18O ranged from 108.34 to 114.89 and the average value was 112.77;and temperature of carbonate deposited ranged from 43.36℃ to 77.84℃,and the average value was62.30℃.Above results,combined with the comprehensive analysis of some geochemical elements,such as major elements,trace elements and organic carbon content,suggested that main diagenetic stage of Miocene clastic rock of Shangganchaigou Formation in Eboliang III tectonic belt was in phase B of early diagenetic stage B or phase A of the middle diagenetic stage.The early stage of diagenesis occurred in dry environment,where the water was cold freshwater or brackish water,and to the late stage of diagenesis,the Z-value of paleosalinity of water clearly decreased,and the paleo-environment was dominated by warm and wet climate.
出处
《沉积学报》
CAS
CSCD
北大核心
2015年第2期337-347,共11页
Acta Sedimentologica Sinica
基金
中国科学院2012年度"西部之光"人才计划支持项目
甘肃省科技计划(自然科学基金)(编号:1308RJZA310)
甘肃省重点实验室专项(编号:1309RTSA041)联合资助
关键词
碳氧同位素
碳酸盐胶结物
上干柴沟组
中新统
鄂博梁Ⅲ号构造带
carbon and oxygen isotopes
carbonate cements
Shangganchaigou Formation
Miocene Series
Eboliang Ⅲ tectonic belt
