冀东地区麻粒岩相岩石中不同世代辉石的研究

STUDIES ON PYROXENES OF DIFFERENT GENERATIONS IN THE GRANULITE FACIES METAMORPHIC ROCKS, EASTERN HEBEI

通过对冀东地区两期麻粒岩相岩石中41个斜方辉石和42个单斜辉石的详细研究,认为辉石矿物普遍存在多世代现象。不同世代辉石的化学成分及共生二辉石对之间元素的分配,均能反映出形成条件的差异,并从温压条件估算的结果进一步得到了证实。

41 orthopyroxees and 42 clinopyroxenes analyized were sampled form the metamorphie rocks in eastern Hebei, in which two granulite facies matamo-rphic eronts took place. Two and three mineral generations can be identified among the orthopyroxenes and clinopyroxenes respectively. The concentrations of A12O3 and CaO in the pyroxees, to jade and Ca- Tchermark Component in the clinophroxees and the distribtion of elements between the Coexisting minerals are indicators of different metamophic environments. The iron content in the pyroxenes is affected chiefly by compositions of the protolites, although metamophic environments also influence it.Geothermometry and geobarometry based on mineral pairs have yielded the information consistent with the conclusions from the analysis, which sggests that the poly-generations of pyroxenes be resuted from variation in metamorphie enviroments.