Characteristics of Mesozoic-Cenozoic structural deformation in the Sarekebayi basin, Xinjiang, and its prospecting significance

Based on field geological survey and structural geological survey, the authors systematically analyzed the geometry, kinematics and dynamics characteristics of the faults and folds which are at the edge and in the interior of the Sarekebayi basin, and reconstructed the evolution process of the basin so as to explore the ore-controlling rules and promote prospecting prediction at the depth. The results are as follows: ① The basin has experienced eight stages of structural evolution. i.e., the development of pull-apart basin (J₁-J₂), the tectonic uplift and denudation (J₂-J₃), the subsidence (J₃), the tectonic uplift and denudation (J₃-K₁), the subsidence (K₁), the tectonic uplift and denudation (K₁-E), the compressive-shear structural deformation (N1), and the compressive structural deformation (N₂-Q). There existed vertical movement of subsidence and uplift in the first six stages (J₁-E) and horizontal movement of compression in the last two stages (N-Q). ② There are two stages of superimposed compressive structural deformation in the basin. In the early stage, the N(W)W-S(E)E-trending open fold with small scale was formed. In the late stage, a series of NEE-SWW trending folds and faults were formed, which showed that southern boundary fault and northern boundary fault on the margin of the basin were thrusting towards the basin, and the associated folds formed in the footwall near the faults (NF, SF) tended to be closed tightly, while the secondary folds in the core of compound syncline (Sf) far away from the faults (NF, SF) were mostly open and wide. ③ Structural ore-control of the basin can be divided into two stages. In the mineralization stage (J₁-K₁), the normal fault, reverse fault and associated fault-joint-crack formed by basin subsidence and uplift were the important ore-passing structures, the bedding fissures developed in the sandy conglomerate layer of Kuzigongsu Formation of Upper Jurassic were the important ore-storage structures, and the intersectional parts of ore-passing structures and ore storage structures were the best location for ore fluid enrichment and mineralization. In the post mineralization stage, the compressive structural deformation formed by the late (N₂-Q) NNW-SSE regional compression obviously controlled the spatial distribution of the orebody, resulting in the involvement of the orebody in the fold deformation as well as it being cut through or staggered by the fault-crack zone. ④ In the east zone of the 30th prospecting line, Cu or Zn orebodies or mineralization bodies probably occurred in the second lithologic section of Kuzigongsu Formation, which was concealed in the depth of southern ore zone, and it has great potential for prospecting.