岩石矿物学杂志2011，Vol.30Issue(2)：243-258,16.
南天山满大勒克蛇绿岩铬铁矿矿物学特征及其意义
Mineralogy of chromites in Mandaleke ophiolite of South Tianshan Mountains and its geological implications
摘要
Abstract
The Mandaleke ophiolite belongs to the late Paleozoic ophiolite belt in South Tianshan Mountains and is composed of serpentinized peridotites, basalts and radiolarian cherts.The chromite or Cr-spinel occurs in the serpentinized peridotites as a ubiquitous accessory mineral, some of which has the podiform texture.Petrographic observation and electron microprobe analysis indicate that the Cr-spinel grains display obvious composition zoning, suggesting the path of such thermal events as crystallization, upwelling and alteration.The core of the Crspinel crystal represents the provenance where the mineral crystallized.The authors thus chose cores of the Crspinel to trace the nature of the mantle and the whole crystals to deduce the thermal events that the host rocks have experienced.On the basis of olivine-spinel geothermometry, the crystallized temperature of the anhedral core is estimated to be from 1359℃ to 1394℃ , 1379℃ on average.Similarly, according to the Cr-spinel geobarometer, the mantle pressure is estimated to be from 2.76 GPa to 3.00 GPa, 2.87 GPa on average, while the oxygen fugacity relative to FMQ buffer is FMQ - 1.50~ FMQ - 2.92 log units, FMQ -2.14 log units on average.Furthermore, the degree of partial melting of the mantle is estimated to be from 16.7％ to 18.0％, 17.3％ on average, in the light of its relationship with Cr#.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-discrimination diagrams imply that the Mandaleke ophiolite was formed in a fore-arc setting.The compositional zoning suggests that the peridotites have undergone a thermal path of decreasing temperature and increasing oxygen fugacity.It can be inferred that the mantle peridotites experienced the process from a high temperature and high pressure mantle (lower oxygen fugacity) stage to a thrusting slice stage to reach the crustal surface, where they were subjected to regional metamorphism (higher oxygen fugacity).关键词
铬尖晶石/成分分带/物理化学条件/构造背景分类
天文与地球科学引用本文复制引用
张炜斌,张东阳,张招崇,黄河,赵莉..南天山满大勒克蛇绿岩铬铁矿矿物学特征及其意义[J].岩石矿物学杂志,2011,30(2):243-258,16.基金项目
国家科技支撑项目(2007BAB25B05) （2007BAB25B05）
111计划(B07011) （B07011）
教育部创新团队计划资助项目 （）
