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引用本文:陈印,冯晓曦,陈路路,金若时,苗培森,司马献章,苗爱生,汤超,王贵,刘忠仁. 鄂尔多斯盆地东北部直罗组内碎屑锆石和铀矿物赋存形式简析及其对铀源的指示[J]. 中国地质, 2017, 44(6): 1190-1206.
CHEN Yin,FENG Xiaoxi,CHEN Lulu,JIN Ruoshi,MIAO Peisen,SIMA Xianzhang,MIAO Aisheng,TANG Chao,WANG Gui,LIU Zhongren. An analysis of U-Pb dating of detrital zircons and modes of occurrence of uranium minerals in the Zhiluo Formation of northeastern Ordos Basin and their indication to uranium sources[J]. Geology in China, 2017, 44(6): 1190-1206(in Chinese with English abstract).
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鄂尔多斯盆地东北部直罗组内碎屑锆石和铀矿物赋存形式简析及其对铀源的指示
陈印1,2, 冯晓曦1,2, 陈路路1,2, 金若时1,2, 苗培森1,2, 司马献章1,2, 苗爱生3, 汤超1,2, 王贵3, 刘忠仁3
1.中国地质调查局天津地质调查中心, 天津 300170;2.中国地质调查局铀矿资源重点实验室, 天津 300170;3.中国核工业二〇八大队, 内蒙古 包头 014010
摘要:
鄂尔多斯盆地作为中国重要的多种能源共生的大型盆地,发育了大量的砂岩型铀矿床。本次工作选择盆地东北部纳岭沟铀矿床作为研究对象,在直罗组含矿段附近采取5个砂岩样品进行碎屑锆石U-Pb定年,并针对含矿样品进行电子探针分析。该地区直罗组含矿段碎屑锆石U-Pb年龄集中分布于5个阶段:(2479±11)Ma~(2460±19)Ma、(2300~1950)Ma、(1896±21)Ma~(1820±32)Ma、(316~266)Ma及165 Ma。同时,本文整理了鄂尔多斯盆地北部造山带内古老变质基底、孔兹岩带和晚古生代侵入岩时代,并发现在直罗组内获得的碎屑锆石年龄与北部造山带内地质体所记录的年龄相一致。结合前人地球化学及古地理研究,本次工作推断纳岭沟地区直罗组砂岩沉积物最终来自于鄂尔多斯盆地北部造山带。纳岭沟铀矿床内铀矿赋存形式主要为存在于碎屑颗粒内部、黏土矿物周边、黄铁矿周边和炭屑裂隙内部。结合野外地质体放射性异常测量,本次工作认为铀源主要来自于沉积成岩阶段含铀碎屑颗粒的预富集和后期高放射性异常地质体通过含铀含氧水向盆地内部的迁移。
关键词:  鄂尔多斯盆地  直罗组  碎屑锆石  U-Pb定年  铀矿
DOI:10.12029/gc20170611
分类号:P619.14;P597+.3
基金项目:国家重点基础研究计划(973计划)(2015CB453006)、国家青年自然科学基金(41502195)和中国地质调查局地质调查项目(DD20160127)共同资助。
An analysis of U-Pb dating of detrital zircons and modes of occurrence of uranium minerals in the Zhiluo Formation of northeastern Ordos Basin and their indication to uranium sources
CHEN Yin1,2, FENG Xiaoxi1,2, CHEN Lulu1,2, JIN Ruoshi1,2, MIAO Peisen1,2, SIMA Xianzhang1,2, MIAO Aisheng3, TANG Chao1,2, WANG Gui3, LIU Zhongren3
1.Tianjin Geological Survey Center of China Geological Survey, Tianjin 300170, China;2.Key Laboratory of Uranium Mineral Resources, China Geological Survey, Tianjin 300170, China;3.No. 208 Geological Party, BOG, CNNG, Baotou 014010, Inner Mongolia, China
Abstract:
The Ordos Basin is an important large basin with multi-energy resources, around which a series of sandstone-type uranium deposits are developed. The Nalinggou uranium deposit located in the northeastern part was chosen as a study object. Five sandstone samples surrounding the ore-bearing segment in the Zhiluo Formation were selected to make detrital zircon U-Pb dating, while electron microprobe analysis was performed for some sandstone samples with uranium minerals. The ages are distributed as 5 major peaks:(2479±11) Ma-(2460±19) Ma, (2300-1950)Ma, (1896±21) Ma-(1820±32) Ma, (316-266) Ma and 165 Ma. The authors further arranged the age data of metamorphosed basement, khondalite belt and Late Paleozoic intrusions in the orogenic belt on the north margin of the Ordos Basin. These zones of detrital zircons ages are consistent with the ages of geological bodies in the orogenic belts on the northern margin of the Ordos Basin. Combined with the previous work about geochemistry and paleogeography, the authors hold that the provenance of sandstone of Zhiluo Formation in Nalinggou area was finally derived from the orogenic belt on the northern margin of the Ordos Basin. The uranium minerals are spread in and around the clastic grains, clay minerals, pyrites, and fractures in charcoal fragments. The radioactive anomaly measurement in the field work shows that the uranium source probably came from the pre-enrichment of clastic grains from the provenance at the diagenetic stage, and from the migration of the uranium-and oxygen-bearing water through later leaching of the highly radioactive bodies of the provenance.
Key words:  Ordos Basin  Zhiluo Formation  detrital zircon  U-Pb dating  uranium deposit