摘要
金宝山岩体赋存有我国最大的铂族元素矿床,位于云南省弥渡县,大地构造位置处于杨子地台西缘南端。岩体是呈似层状(岩席)产出的小型超镁铁岩,侵位于泥盆系金宝山组白云岩、泥灰岩、砂板岩中,由橄榄岩、辉橄岩及微辉岩、辉石岩异离体组成,没有完整的相带分异,缺乏分异堆积特征。但岩体铂族元素成矿以铂钯为特征(Pd/Ir>10),硫化物Ni/Cu比值低(0.5～5),岩石稀土元素富集,配分型式为轻稀土富集型,体现基性岩浆衍生产物的岩石地球化学特点。元素含量的组合变化反映出橄榄石对岩石成分的控制作用,成岩母体可视为橄榄石与熔体两部分组成的混合体系,分析表明岩浆经历了11％的橄榄石结晶和22％左右的斜长石结晶分异,大部分熔体相携带斜长石先期离开岩浆房或被压滤出去,残余熔体携带橄榄石结晶颗粒在构造挤压作用下向上运移侵位成岩。根据岩浆演化过程反演,计算得到金宝山超镁铁岩原始岩浆组成,表明为低钛拉斑玄武岩岩浆,MgO含量为12.93％,其形成可能与裂谷作用早期的地幔热柱作用有关,原始岩浆起源于未亏损地幔的部分熔融。
The Jinbaoshan intrusion, situated in Midu county, Yunnan, host the largest PGE deposits of our country.This small ultramafic intrusion is composed of dunite, Iherzolite as well as pyroxenite, intruded in Jinbaoshan group at Devonian. No accumulated or zoned petrographical features are recongnized, but the mineralization and REE distribution patterns show that it is a cumulate of basic magma rather than ultramafic one. Compositional relationship in terms of molecular ratio shows olivine controlled rock's composition variations, it can be presumed that the intrusion was formed by a mixture of melt and olivine. Most part of magma experienced 11% olivine crystallization and 22% plagioclass, plagioclass was kneaded out from magma chamber; then the residual melt was mixed with crystallized olivine intruded to be the ultra-mafic intrution. Based on the inversion of magma evolution, the primary magma composition is calculated. It is a kind of low-Ti tholeiite magma containing 12. 93% MgO. According to REE contents the primary magma was originated from partial melting of garnet Iherzolite by diapiric uprise in mantle.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2002年第1期70-82,共13页
Acta Petrologica Sinica
基金
中国科学院知识创新工程(KZCX2-101)资助.
