超高压榴辉岩中磷灰石的针状出溶物及其成因  

NEEDLE-LIKE EXSOLUTIONS FROM APATITE IN ULTRAHIGH-PRESSURE ECLOGITE AND THEIR GENESIS

作　　者：洪吉安[1] 李曙光[1] C.T.William 杨学明[1] 

机构地区：[1]中国科技大学地球与空间科学学院,安徽合肥230026 [2]Department of Mineralogy,Natural History Museum,Cromwell Road,London SW7 5BD,UK

出　　处：《矿物学报》2003年第3期273-277,共5页Acta Mineralogica Sinica

基　　金：国家重点基础研究发展规划项目(G199075503)

摘　　要：金河桥榴辉岩是一含柯石英的超高压榴辉岩,其中的磷灰石中发现有针状出溶物,这些针状矿物长轴方向平行于磷灰石的c轴。根据电子探针分析结果,出溶物可能是以下三种矿物:独居石、黄铜矿和硅钍石(?)。它们的主要组成元素REE、S和Th等可以呈类质同象形式存在于磷灰石中,在超高压的条件下,由于温度相对较低,趋向于从寄主矿物中分离出来。矿物在高压下的这种“自净”行为可能是固态条件下矿物之间微量元素重新分配的一种方式,这种行为可能对地球不同层圈的化学组成演化有特别意义。The eclogite from Jiheqiao is a coesite-bearing ultrahigh-pressure metamorphic rock, in which apatite is bearing three kinds of needle-like exsolved minerals: monazite, chalcopyrite and huttonite. These needles are parallel to the C axis of apatite. The dominating chemical components in the three minerals, rare earth elements(REE) , sulfur(S) and thorium (Th) , are the secondary components in apatite as isomorphous elements. Under very high pressures, these elements can be separated from their host minerals due to relatively low temperature in the subducted zone. The 'self-purification' of minerals under very high pressures may be of special significance for the chemical evolution of the different layers of the Earth, and it may be a way of redistribution of trace elements in the solid state among different minerals.

关 键 词：榴辉岩 磷灰石 针状出溶物 超高压 柯石英 寄主矿物 微量元素 化学组成演化 

分 类 号：P578.92[天文地球—矿物学] P541[天文地球—地质学]