内蒙古太平川钼铜矿床岩石地球化学、热液活动记录与年代学

太平川钼铜矿地处大兴安岭成矿带北段额尔古纳地块内,是典型的斑岩型矿床。岩石Na_2O、K_2O、CaO含量变化是斑岩矿床热液蚀变的重要指示要素,蚀变(矿化)斑岩中Na_2O、K_2O的含量均低于未蚀变斑岩,而MgO、CaO、TiO_2、MnO、FeO则明显升高。通过对矿床中菊花状、鳞片状辉钼矿和斑岩侵入体中细脉状、浸染状辉钼矿Re-Os同位素测定,分别获得(202.1±9.4)Ma(MSWD=10.8)、(187.8±5)Ma(MSWD=0.17)的等时线年龄。斑岩体(脉体)侵入过程中热液活动记录与蚀变、成矿关系密切。太平川斑岩型钼铜矿床含矿斑岩体是印支末期—燕山早期碰撞造山作用背景下,新元古代增生的额尔古纳地块内花岗质地壳物质重熔形成的。

Petrogeochemistry, records of hydrothermal activities and geochronology of the Taipingchuan Mo-Cu Deposit, Inner Mongolia

The Taipingchuan Mo-Cu deposit, located in Eerguna block, northern Daxingan mountain metallogenic belt, a typical porphyry deposit. The change of Na₂O, K₂O and CaO compositions in porphyry rocks are important indicators of hydrothermal alternation within porphyry deposit.The contents of Na₂O and K₂O in altered porphyritic rocks are lower than that in unaltered porphyritic rocks but the contents of MgO,CaO, TiO₂, MnO and FeO are higher than in unaltered rocks. The hydrothermal activities are closely associated with alternation and porphyritic mineralization during the process of porphyritic mass (veins). Based on the Re-Os isotopic measurement of daisy-like, scale-like molybdenite minerals collected from the deposit area, and veinlet and disseminated molybdenite minerals collected from porphyritic intrusion, the isochron ages are as followings as (202.1±9.4)Ma(MSWD=10.8), (187.8±5)Ma(MSWD=0.17)respectively. It indicted that the ore-bearing porphyritic intrusion in the Taipingchuan porphyry Mo-Cu deposit area, are formed from remelting substances of granitic rocks accreted in Neo-proterozoic Eerguna block in the tectonic setting of collisional orogenesis from late Indosinian period to early Yanshan period.