矿床地质2013，Vol.32Issue(3)：515-532,18.
会理菜子园镍矿床方辉橄榄岩铂族元素、Re-Os同位素及其地质意义
Platinum group elements and Re-Os isotope geochemistry of harzburgites from Caiziyuan nickel deposit in Huili County of Sichuan Province and its geological significance
摘要
Abstract
There exist lots of basic-ultrabasic rock bodies in the Caiziyuan laterite type nickel deposit in Huili County of Sichuan Province.Geochemical characteristics of Platinum group elements(PGEs) and Re-Os isotope of three peridotites rock bodies are reported in this paper.The lithogcochemistry of the Caiziyuan deposit shows high MgO and low SiO2,Al2O3,Na2O and K2O content as well as high Mg# values.CIPW calculation indicates that the main standard minerals of the Caiziyuan deposit are composed of olivines and hypersthenes (the volume fraction is more than 90 percent),showing that the Caiziyuan deposit belongs to magnesia harzburgite type.The ∑ PGE of the Caiziyuan deposit is relatively lower than that of most mantle residual peredotites,implying that PGE was extracted by the sulfides in the basic magma resulting from the large melt fractions of mantle at the early stage.The differentiation between PPGE and IPGE in the Caiziyuan deposit is obvious,and is similar to things of mantle residual peridotites at the bottom of normal ophiolite suites reported earlier.The right-oblique mantle normalized PGE patterns are controlled mainly by the high partial melting of the mantle.Pt is concentrated relative to Pd in PPGE,and the differentiation between Pt and Pd might have been caused by obvious hydrothermal alteration; therefore a small amount of Pt probably exists in the form of residue alloy in Caiziyuan peridotites.The small γ(Os) values imply that Caiziyuan peridotites were derived from the mantle with a fine Re-Os isotope sealing system.The petrogeochemistry,platinum group elements and Re-Os isotopic geochemistry suggest that the Caiziyuan deposit was derived directly from the mantle,thus belonging to the residual harzburgite at the bottom of the normal ophiolite suite.Caiziyuan ophiolite may be a part of the relics of ancient ocean floor of small ocean basin,implying that Kunyang rift was evolved into small ocean basin where Huili Group was deposited in the late period of Mesoproterzoic.The ophiolitic characteristics of the Caiziyuan deposit further prove that the Huili Group collided with Dongchuan and Tangdan Group in the south of Caiziyuan-CaimashuiMatang fault belt at the end of Mesoproterozoic,and that the basement in the southwest of Yangtze craton was probably collided and collaged by small continental segments in different periods,resulting in the basal continental crustal accretion.关键词
地球化学/菜子园橄榄岩/铂族元素/Re-Os同位素/蛇绿岩/昆阳裂谷/会理群/东川群/汤丹群/会理Key words
geochemistry/ Caiziyuan peridotites/ platinum group elements/ Re-Os isotope/ ophiolite/ Kunyang rift/ Huili Group/ Dongchuan Group/ Tangdan Group/ Huili分类
天文与地球科学引用本文复制引用
王生伟,孙晓明,廖震文,屈文俊,杨波,蒋小芳,李超,李永灿..会理菜子园镍矿床方辉橄榄岩铂族元素、Re-Os同位素及其地质意义[J].矿床地质,2013,32(3):515-532,18.基金项目
本文得到国土资源大调查(编号:1212010911064 （）
1212011085162)、国家重点基础研究发展规划(973)项目(编号:2009CB421006)和国家自然科学基金(编号:40173025)的联合资助 （973）
