含煤盆地表生热液铀成矿理论及证据：以伊犁盆地南缘及鄂尔多斯盆地东北部侏罗系为例

基于伊犁盆地南缘及鄂尔多斯盆地东北部侏罗系砂岩铀矿露头剖面与岩心观察、扫描电镜及显微薄片测试与分析、有机质成熟度测试以及前人研究成果，认为砂岩铀矿中常见的红、褐色“氧化带”砂岩及“过渡带”白色砂岩属于烧变岩，提出表生热液的概念，由此将煤层自燃与砂岩铀矿的形成联系起来，提出中国北方含煤盆地煤层自燃促进铀的富集成矿的设想。即煤层在新生代干旱气候条件下自燃，在相对湿润气候条件下大气降雨影响煤的自燃，形成表生热液，携带从自燃煤层及附近高温烧烤岩层中释放的 U6＋沿渗透性岩层流动，在流动遇阻及温度降低条件下铀元素从（已经降温的）表生热流体中析出，并富集成矿。该成矿模式对中国北方陆相盆地“层间氧化带”、“潜水氧化带”砂岩型铀矿提出新的成因解释。其证据主要体现在：（1）烧变岩与铀矿在空间上的相关性；（2）“氧化-还原带”砂岩微观特征；（3）铀石激光原位同位素年龄测定数据；（4）伊犁盆地煤等有机质成熟度；（5）伊犁盆地及鄂尔多斯盆地方解石胶结物流体包裹体测试数据；（6）鄂尔多斯盆地北部同位素测试数据等。该模式合理解释了砂岩型铀矿主要分布于中国北方的原因，预示着煤层自燃形成的烧变岩及（近地表）表生热液疏导体系是陆相含煤盆地表生热液砂岩型铀矿主要的找矿标志。

Theory of uranium mineralization caused by supergene hydrothermal fluid in coal-bearing basins:Evidences from Jurassic sandstone in southern Yili Basin and northeastern Ordos Basin,China

The data of field outcrop investigation,drilling core observation and the analysis of thin sections and measurements of SEM,organic matter maturity,in southern Yili Basin and northeastern Ordos Basin reveal that the Jurassic red sandstone of oxidized zone and white sandstone of transitional zone in the uranium ore deposits are the special types of burnt rock.The supergene hydrothermal fluid is considered to be the cause of sandstone uranium ores in coal-bearing basins,i.e.,the coal beds were self-burning in the dry climatic conditions and then the supergene hydrothermal fluid formed during the relatively humid climatic period due to the atmospheric rainfall.U6 + was released from the burning coal beds and high-temperature burnt rocks and in turn was carried by the supergene hydrothermal fluid flowing in the permeable beds,such as sandstone layers and unconformity.Then the uranium element was separated out from the supergene hydrothermal fluid and deposited as ores in the sandstone when the flowing fluid blocked and the temperature declined.This model provides a new interpretation for the sandstone type uranium of interlayer oxidation zone and phreatic oxidation zone in the continental coal-bearing basins in northern China.The above interpretation is evidenced by (ⅰ)the relationship between the burnt rock and uranium mine,(ⅱ)the microscopic features of sandstone in oxidized zones and reduced zones,(ⅲ)laser isotopic dating of uranium ores,(ⅳ ) measurement of organic matter maturity for Jurassic coal in Yili Basin, (ⅴ )analysis of fluid enclosures of Jurassic calcite cement in Yili Basin and Ordos Basin and (ⅵ)C,O and H isotopes of calcite cement in northern Ordos Basin.The uranium mineralized model of supergene hydrothermal fluid interpreted why sandstone uranium deposits mainly distribute in northern China.Burnt rock and permeable rocks suitable for migration of supergene hydrothermal fluid are indicators for uranium ores in the area.