摘要
在塔里木盆地下第三系储层砂岩中 ,碳酸盐是分布最广的自生矿物之一 .其形成从早成岩期延续到了晚成岩期 .成分以方解石为主 ,白云石亦常见 ,二者均含数量不等的铁锰 .分析结果显示 ,自生碳酸盐 δ13C值分布范围在 - 31‰～ +6‰ ,大部分样品介于 - 12‰～ +3‰之间 .δ18O值变化范围在12 .4‰～ 2 8.5‰ ,样品在 18‰～ 2 4‰组区间相对集中 .其碳氧同位素变化范围远远高于沉积碳酸盐 ,并且有不同的众数计算表明与自生碳酸盐平衡的水相氧同位素组成具双峰正态分布 .δ18O值在 - 4‰～ - 2‰和 4‰～ 6‰各有一个峰值 ,前者具封存盐卤水特征 ,后者反映了成岩过程泥质沉积物的脱水作用及水岩反应 .与自生碳酸盐平衡的 CO2 δ13C值最高频数出现在 - 4‰～ - 8‰组区间 .此类 CO2 应来自上地幔 .另有部分 CO2 来自生油岩热解作用 。
Carbonate is one of the most widely developed authigenic minerals in Low Tertiary reservoir sandstones found in Tarim Basin. Its formation commenced in eodiagenesis and continued to mesodiagenesis. Calcite is the dominant, and dolomite the common component, both with a certain amount of Fe and Mn. Analysis result shows that δ 13 C value of the authigenic carbonate varies in a range of -31‰~ +6‰, but in -12‰^+3‰ for most samples. δ 18 O value is in 12.4‰~28.5‰, but mainly concentrated in 18‰~24‰. The C O isotope composition is much more variable than that of sedimentary carbonate, and in addition, with a different mode. The calculated oxygen isotope composition of the aqueous fluid in equilibrium with the authigenic carbonate possesses a bi model distribution pattern. Two frequency peaks of δ 18 O value are found at -4‰^-2‰ and 4‰~6‰ respectively. The former features buried saline water, while the later reflects the dehydration of argillaceous sediments and diagenetic water rock reaction. The highest frequency of δ 13 C value of CO 2 in equilibrium with the carbonate is -4‰^-8‰. This group of CO 2 most probably comes from the upper mantle. Some other origins for CO 2 are the thermolysis of source rock and diagenetic decomposition of marine carbonate.
出处
《浙江大学学报（理学版）》
CAS
CSCD
2001年第3期321-326,共6页
Journal of Zhejiang University（Science Edition）
基金
"九五"国家科技攻关项目!(96 1110 10 2 0 7)
