期刊
JOURNAL OF ASIAN EARTH SCIENCES
卷 34, 期 3, 页码 336-346出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jseaes.2008.06.001
关键词
Eclogite; Garnet pyroxenite; Kimberlite; Xenolith
Mafic xenoliths of garnet pyroxenite and eclogite from the Wajrakarur, Narayanpet and Raichur kimberlite fields in the Archaean Eastern Dharwar Craton (EDC) of southern India have been studied. The composition of clinopyroxene shows transition from omphacite (3-6 wt% Na(2)O) in eclogites to Ca pyroxene (<3 wt% Na(2)O) in garnet pyroxenites. Some of the xenoliths have additional phases such as kyanite, enstatite, chromian spinel or rutile as discrete grains. Clinopyroxene in a rutile eclogite has an X(mg) value of 0.70, which is unusually low compared to the Xmg range of 0.91-0.97 for all other samples. Garnet in the rutile eclogite is also highly iron-rich with an end member composition of PrP(26.5)AIM(52.5)Grs(14.7)Adr(5.1)TiAdr(0.3)SPS(1.0)UV(0.1). Garnets in several xenoliths are Cr-rich with up to 8 mol% knorringite component. Geothermobarometric calculations in Cr-rich xenoliths yield different P-T ranges for eclogites and garnet pyroxenites with average P-T conditions of 36 kbar and 1080 degrees C, and 27 kbar and 830 degrees C, respectively. The calculated P-T ranges approximate to a 45 MW m(-2) model geotherm, which is on the higher side of the typical range of xenolith/xenocryst geotherms, (35-45 MW m(-2)) for several Archaean cratons in the world. This indicates that the EDC was hotter than many other shield regions of the world in the mid-Proterozoic period when kimberlites intruded the craton. Textural and mineral chemical characteristics of the mafic xenoliths favour a magmatic cumulate process for their origin as opposed to subducted and metamorphosed oceanic crust. (C) 2008 Elsevier Ltd. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据