苦橄岩体中的一种矽卡岩  

The Skarns in Xujiachong Picrite Body from Jingshan County,Hubei Province

作　　者：俞惠隆 Yu Huilung

机构地区：[1]湖北地质学校

出　　处：《岩矿测试》1985年第2期108-114,共7页Rock and Mineral Analysis

摘　　要：近数年来,笔者等在野外调查期间,于湖北省京山县徐家冲苦橄岩体中发现三个白云岩捕虏体。本文描述的一种矽卡岩,实际上就是这些白云岩捕虏体遭受矽卡岩化的产物。经过岩石薄片的系统鉴定和人工重砂的分析对比,最后将这种矽卡岩定名为钙铁榴石-透辉石矽卡岩。The skarns in the Xujiachong from Jingshan county,Hubei Province,are virtually the products of dolomitic xenoliths suffered contact-thermal metamor-phism and contact metasomatism,and may be divided mainly into two types:monticellite-andradite-diopside skarn with porphyroblastic texture in the outer zone of xenolith and andradite-diopside skarn with fine grained granoblastic texture in its inner.Their mineral assemblages are shown as following;diopside,andradite,monticellite,biotite,perovskite,ilmenite and titanite in outer zone of xenolith and diopside,andradite,biotite,rutile,magnetite,apatite and zircon in its inner zone.The rock-forming minerals of andradite-diopside skarns are mainly diopside,andradite,monticellite and biotite,whereas the accessory minerals consist of perovskite,ilmenite,rutile,titanite,magnetite,apatite and zircon.The monticellites were suffered intense serpentinization(always occurs as pseudomorphs after olivine),and sometimes altered to vesuvianite,occuring as porphyroblastics in the outer zone of xenolith.The andradites are the most common in these rocks,which occur not only as porphyroblastics,but also as fine grains in the matrix.Their structural formula is shown below.(Ca_(2.735),Mg_(0.20),Fe_(0.035)^(2+))_(3.00)(Fe_(1.85)^(3+),Ti_(0.05),Al_(0.10))_(2.00)(Si_(12.916),Al_(0.074))_(2.99)O_(12.00)The crystallization history and the temperature conditions for formation of the andradite-diopside skarns are discussed by the authors in this paper,and according to Evans and Trommsdorff(1980),using the H.G.F.Winkler method(1975),the equilibium temperatures for coexisting of monticellite and andradite pair in the skarns are calcutaled at 680°-700℃.

关 键 词：矽卡岩 白云岩 钙铁榴石 捕虏体 岩石薄片 苦橄岩 湖北省京山县 透辉石 

分 类 号：P61[天文地球—矿床学]