二连盆地反转构造与砂岩型铀矿成矿作用

Inversion Structure and Its Relationship with Sandstone Type Uranium Metallization in Erlian Basin

笔者将二连盆地的形成与演化划分为初始断陷(J1-2)与反转期(J3)、强烈断陷(K1a-K1t)与反转期(K1s1)、坳陷(K1s2)与强烈反转期(K2e-E2y)等3个断陷(坳陷)沉积作用与反转作用期的交替演化过程。在不同的反转构造期,其反转类型、反转形态和反转程度不一。研究发现,在反转背斜构造核部、反转鼻状构造及强烈反转单斜构造部位,赛汉组下段主要发育潜水氧化带型铀矿化;而在反转背斜构造的两翼、较强烈和中等程度的反转单斜构造部位,赛汉组上段古河道内发育潜水-层间氧化带型铀矿化;在微弱反转构造区,砂岩型铀矿的成矿作用不发育。据此,通过磷灰石裂变径迹反演和镜质体反射率反演,估算了赛汉晚期以来的剥蚀厚度,查明二连盆地反转构造的强弱分布,提出有利于砂岩型铀矿成矿的区段。

In this paper, the formation and involution of Erlian basin was divided into 3 alternative stages： initial faulting（J1-2） and initial inverse（J3） stage, intense faulting（K1 a-K1 t） and inverse（K1 s1） stage, depression（K1 s2）and intense inversion（K2-E2）. The inversion type, shape and intensity are different in different inversion stage. It can be inferred that inversion structure core of anticline, inversion nose structure and intense monocline inversion structure in the lower member of Saihan formation were favor to develop phreatic oxidation sandstone uranium. Inversion structure limbs of anticline, sub-intense and moderate monocline inversion structure were favor to develop phreatic-interlayer oxidation sandstone uranium in paleo-channel of the upper member of Saihan formation. However, poor uranium mineralization were developed in slight inversion structure areas.Therefore, apatite fission track and vitrinite reflectance method were used to estimate the erosion thickness and distribution of inversion structure intensity since Saihan formation in Erlian basin, and favorable mineralization zones for sandstone uranium were proposed.