中国北方主要中新生代盆地构造沉积气候演化及其成煤、铀意义

Tectonic,Sedimentary,and Climate Evolution of Meso-Cenozoic Basins in North China and its Significance of Coal Accumulation and Uranium Mineralization

中国北方中新生代盆地往往叠加发育煤炭和可地浸砂岩型铀矿。大致以鄂尔多斯‒银额盆地为界,中国北方东、西部主要含煤、铀盆地在构造演化、充填历史和成矿年龄等方面均存在明显差异,但不同盆地煤、铀空间配置却表现出相似的“下黑‒中灰‒上杂”三段式展布规律。为进一步探讨盆地构造、沉积、气候演化规律及其对成煤、铀的制约,在对比分析东、西部盆地动力学机制和典型煤、铀成矿特征的基础上,以盆地成煤、成铀期及期后的构造演化史为主线,总结东、西部盆地中生代古气候演变特征和沉积演化规律,指出中国北方中生代盆地构造、沉积、气候演化的差异是东、西部成煤、成铀差异的主因,但所有含煤、铀盆地均经历了“暖湿气候快速沉降期大可容纳空间湖沼相有机质富集期、温暖‒半干旱气候缓慢沉降期小可容纳空间辫状河‒辫状河三角洲相有利砂体发育期、干旱‒半干旱气候多期次隆升剥蚀成铀期”三段式构造‒沉积演化成矿过程。对中国北方中新生代盆地的含铀性评价、铀成矿远景预测具有较好的判别意义。

The Meso-Cenozoic basins in North China are mostly energy basins with superimposition of coal and uranium resources.Divided roughly by the Ordos Basin-Yin’e Basin,the basins in the eastern and western parts have obvious different history of tectonic evolution,basinal filling,and uranium ore-forming ages.Nevertheless,these two types of basins show similar stratigraphic distribution of coal series in the lower parts and uranium-bearing rock series in the upper parts.To further explore the tectonic,sedimentary and climatic interaction of the basins and its constraints on coal and uranium formation,comparative analyses of dynamics mechanism and metallogenic characteristics of basins in the eastern and western parts were carried out,and the Mesozoic-Cenozoic paleoclimate and sedimentary evolution were summarized.It is concluded that the“interaction of tectonic sedimentary and climate”is the main mechanism of the symbiosis of coal and uranium in these basins.All these coal and uranium-bearing basins have undergone three-stage of tectonic sedimentary evolution and ore-forming process.That is,(1)the accumulation of organic matter during the rapid subsidence period under humid and hot climate;(2)the development of alluvial fan-river-delta sand body during the slow subsidence under warm and humid climate;(3)the uplift and denudation in the multi-stage structural inversion period and alteration by oxygen and uranium bearing fluids under arid climate.This is of great significance to the evaluation of uranium-bearing properties and uranium metallogenic prospects in the Mesozoic and Cenozoic basins in North China.