宁芜盆地蒋庙橄榄辉长岩的岩相学和矿物学特征及其构造意义

PETROGRAPHIC AND MINERALOGICAL CHARACTERISTICS OF JIANGMIAO OLIVINE GABBROS IN THE NINGWU BASIN AND IT IMPLICATION FOR TECTONICS

宁芜盆地内有若干基性侵入岩体分布,对其中的蒋庙橄榄辉长岩的岩相学和矿物学特征研究表明:蒋庙橄榄辉长岩中斜长石An从47.68到61.60,属中长石和拉长石;单斜辉石主要为透辉石和普通辉石,斜方辉石主要为古铜辉石;橄榄石Fo从70.77到72.83,属贵橄榄石。这些矿物的化学特征介于俯冲带和板内辉长岩的矿物化学特征之间,并且与造山后辉长岩的矿物化学特征非常类似,结合蒋庙岩体的全岩主量元素地球化学数据以及同位素年龄分析证实,蒋庙橄榄辉长岩产于造山后的构造环境。

The basic intrusions occurred in the Ningwu basin are of very important significance in better understanding of tectonic and magmatic history of this area. Petrographic and mineralog- ical characteristics of Jiangmiao olivine gabbros are studied by means of electron microprobe analysis （EMPA）. It is revealed that the plagioclase in Jiangmiao olivine gabbros is mainly andesine and labradorite with An value ranging from 47.68 to 61.60,and the clinopyroxene is mainly composed of diopside and augite, and orthopyroxene is mainly bronzite. In the rocks, the mineral of ol- ivine is mainly chrysolite with Fo ranging from 70.77 to 72.83. The chemical characteristics of these minerals are between those of the minerals in gabbros formed in subduction zones and intraplate tectonic setting,moreover,they are also similar to those of the minerals in gabbros formed in a post-orogenic setting. The geochemical data of whole rock major elements and isotopic age of Jiangmiao intrusions indicate that they were formed in a post-orogenic tectonic setting.