北秦岭松树沟接触变质岩的形成温度研究  

Geothermometries of Contact Methmorphic Rocks from Songshugou in North Qinling

作　　者：孙卫东[1] 郑永飞[1] 李曙光[1] 孙勇[2] 张国伟[2] 

机构地区：[1]中国科学技术大学地球和空间科学系 [2]西北大学地质系

出　　处：《中国科学技术大学学报》1997年第1期44-49,共6页JUSTC

基　　金：国家自然科学基金;中国科学院专项基金

摘　　要：本文应用氧同位素和电子探针分析方法测定了北秦岭松树沟阿尔卑斯型超镁铁岩体接触变质带内角闪岩和及其原岩秦岭群斜长角闪片岩的形成温度．角闪岩的角闪石－石榴子石Ｆｅ－Ｍｇ配分温度计给出不同期次形成温度分别是：早期８１５～８５５℃，主期７００～７７０℃．矿物对氧同位素地质测温结果得到，角闪岩的主期变质温度为７４５～７７０℃，与其电子探针结果在误差范围内一致；斜长角闪片岩为５００～６０５℃。The oxygen isotope and electronic probe methods were employed to determine the metamorphic temperature of amphibolite from the contact metamorphic zone in an Alpine-type ultramafic rock and schist from Qinling Group in Songshugou, North Qinling. Mineral-pair Fe-Mg partition geothermometry yields temperatures of 815 to 855 ℃ for the earlier metamorphism and 700 to 770 ℃ for the major metamorphism of amphibolite. Mineral-pair oxygen isotope geothermometry yields temperatures of 745 to 770 ℃ for the amphibolite and 500 to 605 ℃ for the schist. The isotopic temperatures are consistent with the results derived from the Fe-Mg geothermometry and also petrological temperature, indicating oxygen isotope equilibrium within the metamorphic rocks studied. The amphibolite is very close to the ultramafic rock and has thus been influenced by thermal contact metamorphism, resulting in oxygen isotope reequilibration among the minerals. The schist is far away from the ultramafic rock and hence has been little affected by the thermal contact metamorphism. As a result, the isotopic temperatures obtained for the schist can be used to represent the formation temperature of the regional metamorphic rocks in this region.

关 键 词：氧同位素 接触变质 变质岩 形成温度 

分 类 号：P588.3[天文地球—岩石学]