西岭矿区酸性熔岩中石榴石斑晶的特征、成因与成岩意义  

CHARACTERISTICS, GENESIS AND PETROGENIC SIGNIFI-CANCE OF GARNET PHENOCRYSTS IN ACID LAVAS FROM THE XILING MINING AREA

作　　者：陈惜华 赵以起 

机构地区：[1]中南工业大学地质系,长沙410083

出　　处：《地球化学》1991年第1期33-39,共7页Geochimica

基　　金：国家自然科学基金

摘　　要：西岭矿区酸性熔岩中石榴石斑晶属铁铝榴石,是在20-30 kbar压力下较早从岩浆中品出的斑晶矿物;由于斜长石斑晶发生不一致熔融结晶作用,故具有斜长石反应边。酸性熔岩中含有铁铝榴石高压斑晶及铁铝榴石中含有14.42-21.40％的镁铝榴石分子,是岩浆物质来自深源的标志。石榴石是重稀土选择型矿物。西华山黑云母花岗岩中的铁铝榴石是铁铝榴石-锰铝榴石,其特征与成岩成矿意义均不同于西岭矿区铁铝榴石斑晶。According to the determinations of rocks and minerals, electron microprobe analyses and infrared spectrometry data, it has been shown that garnet phenocrysts in acid lavas from the Xiling mining area are greenlandite crystallized as phenocrysts from the magma at the early stage under pressures of about 20-30 kbar. The plagioclase rim of the garnet resulted from incongruent melting of the plagioclase phenocrysts. It is an indicator of tnagmatic derivation from great depth that the acid lavas contain greenlandite phenocrysts formed at high pressure and the greenlandite contains 14.42-21.40% pyrope. The REE distribution patterns show that the garnet is a HREE-selective mineral.In this paper a comparison has been made between the garnet under study and that from biotite granite from the Xihuashan mining area, indicating that the latter garnet is a transitional phase between greenlandite and partschinite. Its characteristics and petrogeno-metallo-genic significance are different from those of greenlandite phenocrysts in the Xiling mining area.

关 键 词：火山岩 铁铝榴石 斑晶 成因 成岩 

分 类 号：P588.14[天文地球—岩石学]