Uranium metallogenesis in South China and its relationship to crustal extension during the Cretaceous to Tertiary
Uranium metallogenesis in South China and its relationship to crustal extension during the Cretaceous to Tertiary
复制标题
白垩纪至第三纪华南铀成矿作用及其与地壳伸展的关系
DOI：
10.2113/gsecongeo.103.3.583
复制
发表时间：
2008-05-01
期刊：
影响因子：
5.8
通讯作者：
Qi, Hua-Wen
中科院分区：
文献类型：
--
作者：
Hu, Rui-Zhong;Bi, Xian-Wu;Qi, Hua-Wen
华南盛产脉状热液铀矿床，赋存于花岗岩、火山岩、炭质和硅质泥质沉积岩中。铀矿床在空间上与伸展构造和/或幔源基性岩脉有关。铀矿床和基性岩脉的年龄均为白垩纪至第三纪，时间上与地壳伸展一致。对12个代表性铀矿床矿脉主成矿期方解石的碳同位素分析表明，成矿流体的δ C-13值主要在-4 ~ -8 / mil之间，表明成矿流体中的CO2可能来源于地幔。地幔成因A与成矿流体He-3/He-4比值（火山型象山铀矿床Ra值为0.10 ~ 2.02）一致。H和0的同位素组成表明成矿流体中的水主要来源于大气。成矿温度范围约为150 ~ 250℃，华南富铀地壳岩可能是铀的来源。地壳伸展和相关的基性岩浆活动被认为加热了岩石，使二氧化碳（可能来自地幔）向上迁移，并与缺乏二氧化碳的大气水混合。富co2热液将烃源岩中的铀动员起来，并沉积在各种寄主岩中，形成铀矿床。
South China is rich in vein-type hydrothermal uranium deposits hosted in granitic, volcanic, and carhonaceous and siliceous pelitic sedimentary rocks. The uranium deposits are spatially associated with extensional structures and/or mantle-derived mafic dikes. Both the uranium deposits and mafic dikes are Cretaceous to Tertiary in age, temporally coincident with the crustal extension. Carbon isotope analyses of calcite deposited in the main-stage mineralization in the veins from 12 representative uranium deposits yield delta C-13 values of ore-forming fluids mainly from -4 to -8 per mil, which are permissive of a mantle origin for the CO2 in the ore-forming fluids. A in mantle origin is consistent with the association of the deposits with mafic dikes and the He-3/He-4 ratios of ore-forming fluids (e.g., 0.10-2.02 Ra for the volcanic-hosted Xiangshan uranium deposit). Isotopic compositions of H and 0 demonstrate that water in the ore-forming fluids is predominantly meteoric in origin. Ore-forming temperatures ranged approximately from 150 degrees to 250 degrees C.Uranium-rich crustal rocks in South China may have been the sources for the uranium. Crustal extension and associated mafic magmatism are considered to have heated the rocks and allowed CO2 (possibly from mantle sources) to migrate upward and to mix with CO2-poor meteoric water. The CO2-rich hydrothermal fluids mobilized uranium from the source rocks and then the uranium was deposited in various host rocks to form the uranium deposits.