陕西汉中地区汉中玉中蛇纹石玉的矿物成分与成因分析

Analysis on mineral composition and genesis of serpentine jade in Hanzhong,Shaanxi

陕西汉中地区发现了较大储量的汉中玉矿床,汉中玉种类繁多,其中以蛇纹石玉储量最大。通过对汉中玉中蛇纹石玉手标本及镜下薄片的观察和研究,总结出了蛇纹石玉的矿物组成特征,其主要矿物成分为蛇纹石,个别样品中发现有方解石、角闪石的蚀变残余物。电子探针分析显示,蛇纹石玉石中的SiO_2含量为41. 5%～44. 5%,MgO含量为35. 4%～39. 7%,其他氧化物含量较低。结合已有地质资料及显微镜观察可推测,汉中玉中蛇纹石玉形成于中酸性岩浆与碳酸岩盐接触的矽卡岩环境中。

Large deposits of Hanzhong jade have been found in Hanzhong area in Shaanxi province.There are many kinds of jade in Hanzhong,among them,serpentine jade reserves the most.The basic Mineralogical characteristics of Hanzhong jade were summarized through observation and study of hand specimens and microscopical thin section of jade.Under the microscope,the composition minerals of serpentine jade observed mainly are serpentine,and calcite minerals and serpentine form metasomatic structure can be found in a few individual samples. Electron probe analysis showed that the content of Si O_2 in serpentine jade was in the range of 41.5%-44.5%,and the content of MgO was 35.4%-39.7%,other ingredients are low. From the existing geological data and microscopic observation,it can be inferred that the serpentine jade in Hanzhong is formed in the silicate environment between intermediate-acid magma contacting with carbonate rock.