摘要
安庆矽卡岩矿床产于月山闪长岩与灰岩重结晶形成大理岩的接触带上。运用氧同位素交换动力学理论研究了月山闪长岩的冷却速率 ,安庆矽卡岩矿床的成因机理、物质来源及演化特征。计算出月山闪长岩体的冷却速率为 10 0℃ /Ma。安庆矽卡岩矿床的形成 ,经历了多期次的成岩成矿作用 ,早期矽卡岩是由闪长岩与大理岩接触交代作用形成的 ,中、晚期矽卡岩及铁矿床是由矽卡岩铁矿浆充填裂隙而成。形成早、中期矽卡岩、铁矿床的流体来源于与富18O大理岩交换后的岩浆水 ,晚期矽卡岩的成岩流体以岩浆水为主 ,有少量大气降水参与。矽卡岩形成之后的石英—硫化物阶段、石英—碳酸盐阶段 ,从早到晚流体中的大气降水逐渐增多。运用矿物的氧扩散动力学 ,解释了透辉石—磁铁矿矽卡岩和斜长石晶体内部的氧同位素非平衡现象。
Anqing skarn deposit occurs in contact zone between Yueshan diorite body and the marble crystallized by sedimentary limestone.This paper has studied cooling rate of Yueshan diorite body and formation mechanism,matter source,evolution characteristic of Anqing skarn deposit using principle of oxygen isotope exchange kinetics.The cooling rate of Yueshan diorite body is 100℃/Ma.Anqing skarn deposit is underwent multistage petrogenetic minerogenesis.The early stage skarn is formed by contact metasomatism between diorite and marble.The middle-late stages skarn and iron ore bodies are filled by skarn-iron ore‘magma’,and their fluids came from the water exchanged between magmatic water and marble with higher δ 18 O value.The fluid of late stage skarn is magmatic water mixed with a little meteoric water.From the quartz-sulfide stage to quartz-carbonate stage,the meteoric water is advance gradually in the fluid after late stage skarn formed.Using the kinetics of oxygen diffusion,the phenomenon of isotope non-equilibrium between diopside and magnetite in diopside-magnetite skarn and between inside and verge of plagioclase crystallization are expounded.
出处
《火山地质与矿产》
2000年第1期23-29,共7页
Volcanology & Mineral Resources
基金
国家自然科学基金!(495 73174)
南京大学成矿作用开放实验室基金资助项目
关键词
矽卡岩矿床
氧同位素
交换动力
安庆
skarn deposit oxygen isotope exchange kinetics Anqing
