新疆阿尔泰乌吐布拉克铁矿床稀土元素地球化学研究

摘要

The medium-sized Wutubulake iron deposit is located in eastern Maizi Basin of the South Altay metallogenic beltmetallogenic belt metallogenic belt metallogenic belt. The ore bodies are hosted in the metamorphosed volcaniclastic-sedimentary sequence of the Upper Silurian-Lower Devonian Kangbutiebao Formation in the form of stratoids or lenses, surrounded by such skarn minerals as garnet, chinopyroxene, scapolite, albite, actinolite,epitote, chlorite and apatite.Ore minerals are mainly magnetite and subordinately pyrite, chalcopyrite,pyrrhotite and molybdenite. Field evidence and petrographic observation indicate four ore-forming stages, i.e.,prograde stage, retrograde stage, sulfide stage and supergene stage. Moat of the wall rocks in the ore district have similar chondrite-normalized REE distribution patterns and are enriched in LREE, with a moderate Eu negative anomaly and a Ce negative anomaly. Amphibolites, which contains magnetite garnet skarn, epidote skarn and ores, have similar chondrite-normalized REE distribution patterns and are enriched in LREE, with an obvious Eu positive anomaly and a moderate Ce negative anomaly, implying that they were formed by magmatic fluids in an oxidation environment. The magmatic fluids are characterized by high temperature and strong enrichment of Eu. The oxygen and hydrogen isotopic data of garnet, quartz and calcite imply that the ore-forming fluids of skam period in the Wutubulake iron deposit were mainly derived from magrnatic water, with the mixture of some minor meteoric water. The carbon and oxygen isotopic data of calcite suggest that the carbon in the fluids was mainly derived from the mantle or deep-seated magma. The δ34S values of sulfide range from 3.7‰ to 10.2‰, with an average of 6.5‰, indicating that the sulfur in the fluids was derived from the volcaniclastic rocks. In combination with the geological characteristics of this ore deposit, the authors hold that the ore-forming material was mainly derived from amphibolite, and the formation of magnetite was closely related to the skarns.%乌吐布拉克中型铁矿床位于阿尔泰南缘成矿带东段麦兹盆地,矿体赋存于上志留统-下泥盆统康布铁堡组变质火山-沉积岩系中,矿体呈似层状、透镜状,矿体及其周围发育大量的矽卡岩矿物.矿区多数围岩的稀土元素配分曲线为轻稀土元素相对富集型,具有中等程度的Eu负异常及中等程度的Ce负异常;斜长角闪岩、含磁铁矿石榴子石矽卡岩、绿帘石矽卡岩及矿石的稀土元素配分曲线表现出相似性,多为轻稀土元素相对富集型,具有强的Eu正异常及中等程度的Ce负异常,表明它们是由一种高温、铕强烈富集的岩浆流体在氧化环境下形成的.结合矿床地质特征,判定乌吐布拉克铁矿床成矿物质来源为斜长角闪岩,磁铁矿的形成与矽卡岩化密切相关.