【作者】 张志欣；

【导师】 杨富全；

【作者基本信息】 中国地质科学院 ， 矿物学、岩石学、矿床学， 2011， 硕士

【摘要】 新疆阿尔泰南缘多金属成矿带是我国重要的成矿带之一,其中铁矿主要产在麦兹和克兰火山沉积盆地中。乌吐布拉克中型铁矿床位于麦兹盆地中,与其它铁矿地质特征相似,是该类铁矿的典型代表,该矿赋矿围岩为上志留-下泥盆统康布铁堡组下亚组第二岩性段黑云母变粒岩、条带状角闪变粒岩、浅粒岩、斜长角闪片岩、斜长角闪岩及大理岩透镜体。矿体呈似层状、透镜状及不规则状产于矽卡岩带中,矿区内发育花岗岩。本论文在充分收集前人资料和野外地质调查的基础上,着重对乌吐布拉克铁矿床地质特征、矽卡岩矿物组合、流体包裹体、稳定同位素、成岩成矿时代、成矿机制方面进行了研究,取得了以下几点认识：(1)矿体呈似层状、透镜状赋存于上志留-下泥盆统康布铁堡组火山-沉积岩系中,矿体内部及周围发育大量矽卡岩。矿石矿物相对简单,主要为磁铁矿其次为磁赤铁矿,少量黄铁矿、磁黄铁矿、黄铜矿、辉钼矿等。脉石矿物主要为石榴石、透辉石、角闪石、绿帘石、绿泥石,其次为黑云母、长石、石英、方解石等。(2)根据野外及室内镜下观察矿物的组合与穿插关系,将成矿作用划分为2期,即矽卡岩期与表生氧化期。矽卡岩期进一步分为3个阶段,即早期矽卡岩阶段、退化蚀变阶段、石英-硫化物-碳酸盐阶段。(3)石榴石端元组分以钙铁榴石-钙铝榴石系列为主,辉石端元组分以透辉石为主,角闪石端元组分主要为铁镁钙闪石,均表现出钙质矽卡岩特点。磁铁矿为岩浆热液型磁铁矿,形成与矽卡岩化密切相关。(4)早期矽卡岩阶段成矿流体属高-中温、高-中盐度、高-中密度的NaCl-H2O体系；退化蚀变阶段成矿流体为中温、中-低盐度、高-中密度的NaCl-H2O体系；石英-硫化物-碳酸盐阶段成矿流体以NaCl-H2O型为主,局部混合有CO2-H2O型流体。(5)早期矽卡岩阶段成矿流体主要来源于岩浆水,而石英-硫化物-碳酸盐阶段成矿流体为岩浆水混合大气降水。硫同位素及岩石和矿石稀土元素特征表明,成矿物质于上志留-下泥盆统康布铁堡组斜长角闪岩。(6)与磁铁矿共生的辉钼矿Re-Os同位素模式年龄为243.6±4.1 Ma与244.2±4.2 Ma,限定铁矿形成时代为早三叠世,首次确定阿尔泰存在三叠纪成矿作用。(7)矿区英云闪长岩和黑云母英云闪长岩锆石LA-ICP-MS U-Pb年龄分别为385.6±2.3 Ma和387.7±2.1 Ma,为中泥盆世早期岩浆活动的产物,早于成矿时代,形成环境为活动大陆边缘的陆缘弧。(8)矿床成因为矽卡岩型,成矿机制可能为早三叠世岩浆热液交代上志留-下泥盆统康布铁堡组火山岩形成矽卡岩矿物,在矽卡岩退化蚀变过程中形成了磁铁矿体。更多还原

【Abstract】 The polymetallic mineralization belt of South Altay is an important metallogenetic belt in Xinjiang, China. The iron deposits are mainly located in the Kelan and Maizi volcaniclastic-sedimentary basin. The medium-sized Wutubulake iron deposit is located in the Maizi basin, its geological characteristics is similar to other deposits, is the typical one of this kind of deposits. The host rocks is biotite granulite, striped hornblende granulite, leptite, amphibolite and marble lense, which is belong to the metamorphosed volcaniclastic-sedimentary sequence of the Upper Silurian-Lower Devonian Kangbutiebao Formation. The ore bodies is hosted in skarns, which occurs as stratoids or lenses, and granite is existed in district. Based on collecting predecessors material and detailed field survey of geological background, focused on the study of geological characteristics, skarn minerals assemble, fluid inclusion, stable isotope, the age of diagenetic and metallogenetic, mineralization mechanism, achieving the summaries as follows.(1) The orebodies which occur as stratoids or lenses is hosted in the metamorphosed volcaniclastic-sedimentary sequence of the Upper Silurian-Lower Devonian Kangbutiebao Formation, surrounding by the skarns minerals. Ore minerals are mainly magnetite, with minor pyrite, pyrrhotite, chalcopyriteand molybdentite etc. Gangue minerals are mainly garnet, chinopyoxene, actinolite, epitote, chlorite, with minor biotite, feldspar, quartz, calcite etc.(2) Filed evidence and petrographic observation indicate two periods of metallogensis, including skarns period and supergene oxidation period. Skarns period is also devide into three stages, including early stage, retrogressive metamorphism stage, quartz-sulfide-carbonate stage.(3) The analytical results of electron microprobe show that the end member of garnet is mainly andradite-almandite, the composition of pyroxene is mainly diopside and the composition of amphibole is mainly ferrotschermakite, all of them show the characteristics of calcic skarn. Magnetite is belong to magmatic hydrothermal type, which is closely related to the skarns.(4) The ore-forming fluids in early stage of skarn period is high-middle temperature, high-middle salinity and high-middle density, which is belong to NaCl-H2O system; The ore-forming fluids in retrogressive metamorphism stage of skarn period is middle temperature, middle-low salinity and high-middle density, which is belong to NaCl-H2O system; The ore-forming fluids in quartz-sulfide-carbonate stage of skarn period is dominantly NaCl-H2O type fulid, locally mixed with CO2-H2O type fluid.(5) The ore-forming fluids in early and retrogressive metamorphism stage of skarn period are mainly derived from magmatic water, while the ore-forming fluids in quartz-sulfide-carbonate stage of skarn period is derived from mixing of magmatic water and meteoric water. The sulfide and rare earth element data of rocks and ores suggest that the ore-forming materials is mainly derived from the amphibolite, which is belong to the metamorphosed volcaniclastic-sedimentary sequence of the Upper Silurian-Lower Devonian Kangbutiebao Formation.(6) Based the Re-Os model ages of molybdentite in magnetite ore rang from 243.6±4.1 Ma to 244.2±4.2 Ma, we concluded that the mineralization age is in the Early Triassic, while have pioneered the the Triassic Mineralization in Altay.(7) LA-ICP-MS U-Pb zircon dating on the tonalite and biotite tonalite in the district, yielded concordant ages of 385.6±2.3 Ma and 387.7±2.1 Ma, indicates that the two plutons were formed at the beginning of the Middle Devonian in continental arc at active extensional continental margin setting, which is earlier than the mineralization age.(8) The Wutubulake iron deposit is belong to skarn type, and the mineralization mechanism is Triassic magmatic hydrothermal interacting with metamorphic volcanic, the formation of magnetite is related to the retrogressive metamorphism of the skarns.更多还原