球粒状緑帘石的结构特征与成因

The Struture and Genesis of Epidote Grains

球粒状緑帘石产出于四川雷波基性火山碎屑岩的晶洞或层间裂隙中,与其共生的有石英、赤铁矿等矿物。镜下研究表明,緑帘石至少有2个世代,第一世代緑帘石呈浅緑色的针状体,集合体为菊花状;第二世代緑帘石呈暗緑色的柱状或楔形,集合体为球粒状或椭球状。它们都由球核与球枝两部分组成,两者间有明显的接触界线,表明球核与球枝不是同时结晶的产物,而是有先后形成关系。EPMA分析表明緑帘石成分中普遍含有较高的SrO（0.51%-1.13%）,与其共生的水晶晶体的流体包裹体测温及拉曼光谱分析表明,气液包裹体主要由H2O及微量CH4组成,,緑帘石属低温（164-177℃）与低盐度（7.31%-7.73%）的热液产物。緑帘石的球粒是在低温、过饱和度大、环境条件转变时快速结晶形成的。

The epidote with the associations of quartz and hematite,occurs as grains in miarolitic cavity in basic volcaniclastic rock,Leibo in Sichuan Province,China.The results indicate that the epidote has at least two generations： light green rosette needles aggregates and dark green granular aggregates.The epidote aggregates generally consist of cores and branches,and between the former and the latter there are clear borderlines,suggesting different crystallizations.The electron-microprobe analyses show that the Sr contents vary from 0.51% to 1.13% of SrO in epidote grains.The Raman spectrum and inclusion thermometric analyses indicate that the hydrothermal fluids are enriched in H2O and CH4.epidote occurs as the product of hydrothermal fluids under temperature 164-177℃ and salinity 7.31%-7.73%.As a whole,epidote grains are formed during the low temperature,high supersaturation and fast variation of the growth environment.