新疆阿尔泰托莫尔特铁(锰)矿成矿作用

摘要

新疆托莫尔特中型铁(锰)矿床赋存于上志留-下泥盆统康布铁堡组上亚组变质火山-沉积岩系中.本研究利用硫同位素和年代学,探讨该矿床的成矿物质来源、成矿时代和成矿作用.结果表明,矿床的形成经历火山沉积期、岩浆热液叠加改造期和区域变质期.火山沉积期为铁和锰主要成矿期,岩浆热液叠加改造期形成少量铁和铜矿化.火山沉积期黄铁矿的δ34S变化于6.2‰ ～ 13.1‰和- 20‰,表明硫主要来自火山岩,也有少量来自细菌还原海水中的硫酸盐.岩浆热液叠加改造期硫化物的δ34S变化于- 1.8‰ ～ 8.5‰,主要集中在-1.8‰～3.8‰,表明硫主要来自黑云母花岗斑岩脉.含矿岩系变流纹岩锆石SHRIMP U- Pb年龄为(406.7±4.3)Ma,穿切矿体的黑云母花岗斑岩脉锆石激光剥蚀-多接收器电感耦合等离子体质谱(LA - MC - ICPMS)U - Pb年龄为(401.6 ±0.6) Ma,表明托莫尔特铁矿火山沉积期形成的Fe - Mn矿化及岩浆热液叠加改造期形成的Fe - Cu矿化出现在早泥盆世(407～401 Ma),为火山喷发沉积和岩浆侵入活动的产物.%The Tuomoerte medium type iron deposit can be found in the metavolcanic-sedimentary sequence of the upper Kangbutiebao Formation from the Upper Silurian to Lower Devonian. The source of ore materials, mineralogenetic epoch and metallogenesis were studied by S stable isotope and geochronology and are reported in this paper. Three periods of mineralization can be distinguished on the basis of field evidence and petrographic analyses; volcano-sedimentation, magmatic-hydrothermal, and regional metamorphism. The majority of the Fe-Mn metallogenic activity occurred during the volcano-sedimentation period, some Fe and the majority of Cu mineralization occurred during the magmatic-hydrothermal period. The 8 S values of pyrite from the volcano-sedimentation period ranged from 6. 2%e to 13. %c and -20%e, indicating that the sulfur was mainly derived from the volcanic rocks, with some minor contributions from the bacteria-reduced sulphate in the se.awater. The S S values of pyrite from the magmatic-hydrothermal period ranged from -1.8%c to 8. 5%c and cluster between - 1. 8%e to 3. 8%e, indicating that the sulfur was mainly derived from the biotite granite porphyry dyke. The zircon U-Pb age by Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry ( LA-MC-ICP-MS) of the meta-rhyolite of the Third Member of upper Kangbutiebao Fm is (406.7 ?.3) Ma, and the age of biotite granite porphyry dyke, which intrude into Fe orebody, is (401.6 ?.6) Ma. The zircon U-Pb ages indicate that the Fe-Mn mineralization period during the volcano-sedimentation and magmatic-hydrothermal periods coincides with early Devonian timing (401 -407 Ma). The Fe-Mn and Fe-Cu mineralization were found to be related to volcanic eruption deposition and magma intrusion activities, respectively.