西北地质2012，Vol.45Issue(4)：346-356,11.
西昆仑库地蛇绿岩铬铁矿中铬尖晶石化学特征及其地质意义
Chemical Characteristics of Cr-spinel of Chromites in Kudi Ophiolite of Western Kunlun and Its Geological Implications
摘要
Abstract
The Kudi ophiolite belongs to the early Paleozoic ophiolite belt in Western Kunlun Mountains and is composed of metamorphic peridotites, cumulate peridotites, basic volcanic rocks and quartzites. The Kudi ophiolite can be divided into four lithofacies, and chromite with the podiform texture occurs in the dunite and pyroxene peridotite facies. In the light of their geochemical composition, the chromites contain the highest Cr2O3 content, maximum Mg # value and minimum Fe # value in the all samples. It can be inferred that the chromites formed a Mg-rich environment and experienced a higher grade of partial melting. On the basis of olivine-spinel geothermometry , the crystallized temperature of the Cr-spinel is estimated to be from 1 366 ℃ to 1 404 ℃, 1 379 ℃ on average. Similarly , according to the Cr-spinel geoba-rometer, the mantle pressure is estimated to be from 2. 98 GPa to 3. 03 GPa, 3. 00 GPa on average. The degree of partial melting of the upper mantle is estimated to be from 17. 33 % to 18. 84 %, 18. 28 % on average. These parameters provide some clues of the physicochemical conditions; these peridotites were derived from garnet lherzolites located in the asthenosphere of the upper mantle, and the incompatible element-depleted mantle might have resulted from previous partial melting , The tectono-discnmination diagrams imply that the Kudi ophiolite was formed in a island-arc island-arc setting overlying subduction zones.关键词
铬尖晶石/物理化学条件/构造背景/库地蛇绿岩/西昆仑Key words
Cr-spinel/ physicochemical conditions/ tectonic setting/ Kudi ophiolite/ western Kunlun分类
天文与地球科学引用本文复制引用
乔耿彪,伍跃中,尹传明,陈登辉,赵晓健..西昆仑库地蛇绿岩铬铁矿中铬尖晶石化学特征及其地质意义[J].西北地质,2012,45(4):346-356,11.基金项目
国家科技支撑项目(2007611007),中国地质调查局地质调查项目(1212011120541) （2007611007）
