【作者】 鲍佩声； 王希斌； 彭根永； 郝梓国；

【Author】 Bao Peisheng Wang Xibin Peng Genyong (Institute of Geology,CAGS,.) Hao Ziguo (Chinese Academy of Geological Sciences)

【机构】 中国地质科学院地质研究所； 中国地质科学院；

【摘要】 西准噶尔豆荚状铬铁矿矿床是尖晶石(或榴石)二辉橄榄岩高度熔融的产物, 分属于两个不同的蛇绿岩系列。高铬型铬铁矿属于地幔橄榄岩-辉石岩-辉长岩系列(简称 PPG 系列),以唐巴勒和萨雷诺海铬铁矿矿床为代表。高铝型铬铁矿属于地幔橄榄岩-橄长岩-(橄榄)辉长岩系列(简称 PTG 系列),以萨尔托海及洪古勒楞铬铁矿矿床为代表。PPG 系列蛇绿岩可能形成于壳层较厚的初始裂开的洋盆或大陆边缘,且可能来自部分亏损的地幔源区；PTG 系列蛇绿岩可能形成于壳层较薄的扩张脊环境,且可能来源于未亏损(或低度亏损)的地幔源区。更多还原

【Abstract】 In western Junggar,there are two types of podiform chromite deposits, i.c.,Cr-high Chromite and Al-high chromite deposits,which belong to dif- ferent lineages of ophiolite respectively.The former belongs to the peridotite- pyroxenitegabbro assemblage(called PPG lineage for short),represented by the Tangbale and Salanuohai chromite deposits,and the latter to the per- idotite-troctolite-(olivine)gabbro assemblage(called PTG lineage for short), represented by the Sartuohai and Hongguleleng chromite deposits.The mantle peridotite of the PTG lineage with a lot of basic segregated materials differs from that of the PPG lineage in having lower MgO,MgO 100/(MgO+FeO) and higher(Ca+Al)100/Si ratios.In addition,the two types are very dif- ferent in accessory and ore-forming chrome spinels as well as in mechanism of mineralization. The podiform chromite deposits are products formed by high-degree partial melting of the pyrolite(spinel or garnet pyrolite).The ophiolite in which Cr-high chromite deposits occur was formed at the initial stage of rifting of an oceanic basin with a thicker crust or at the continental margin and might have come from the partially depleted mantle,while the ophio- lite containing Al-high chromite deposits was formed on the spreading ridge of an oceanic basin with a thinner crust and might have derived from the undepleted(or slightly depleted)mantle. It is considered that the lower spreading rate may be a factor which has contributed to preservation of basic melts as rasidue in mantle peridotits of the PTG lineage as seen in the case of the mineralization of the Sartuo- hal Al-high chromite deposit.更多还原