The Laojiagou is a Middle Triassic porphyry Mo deposit situated in the northern margin of the North China Craton. The Mo mineralization is associated with monzogranite porphyry, and mainly occurs as quartz veins in potassic-, silicic-, sericite-, and propylitic-altered wall-rocks（Zeng et al., 2012）. The alteration/mineralization processes comprise three stages:（Ⅰ） molybdenite+pyrite+quartz,（Ⅱ） pyrite+chalcopyrite+ molybdenite+quartz,（Ⅲ） sulfide-poor+quartz+fluorite. Three types of quartz-hosted fluid inclusions（FIs） were identified（Bodnar et al., 1993; Goldstein et al., 2003）, i.e., aqueous–carbonic（C-type）, liquid-rich two phase（L-type） and rare vaporrich two phases（V-type） FIs. Microthermometric results indicate that the hydrothermal fluids evolved from high-temperature（> 350℃）, low salinity（< 10 wt% NaCl equiv.） and CO2-rich to low-temperature and CO2-poor with major meteoric water input. Hydrogen and oxygen isotopes confirm that source of the hydrothermal fluids had gradually shifted from magmatic-to meteoric water-derived(Stage Ⅰ: δ18OH2O（4.4‰ to 4.8‰） and δDH2O（–105.8‰ to –101.5‰）). LA-ICP-MS zircon U-Pb dating indicates that monzogranite porphyry was emplaced in the early Late Triassic（233±2 Ma; MSWD =0.73）. The monzogranite porphyry samples have high SiO2, K2O and Al2O3, and low MgO and CaO contents, and are high-K calc-alkaline and weakly peraluminous. The rocks are all enriched in light rare earth elements（LREEs） and large ion lithophile elements（LILEs）, but depleted in high field strength elements（HFSEs）. Placing the age and post-collisional geochemical signatures of the monzogranite porphyry into the regional tectonic context, we propose that the Laojiagou porphyry Mo deposit was formed in the early Late Triassic, associated with the post-orogenic extensional tectonics after the closure of the Paleo-Asian Ocean（Chen et al., 2003）.
类型: 国际会议
作者: TANG Wenhao,LI Jian,WANG Keyong,LI Shunda,CAI Wenyan,LIU Hanlun,WANG Yicun
来源: 第九届世界华人地质科学研讨会 2019-06-01
年度: 2019
分类: 基础科学,工程科技Ⅰ辑
专业: 地质学,矿业工程
单位: College of Earth Sciences, Jilin UniversityKey laboratory of Mineral Resources Evaluation in Northeast Asia, Ministry of Land and Resources of China
分类号: P618.65
DOI: 10.26914/c.cnkihy.2019.028350
页码: 132
总页数: 1
文件大小: 175k
下载量: 3
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