在个旧锡铜多金属矿集区发育有矽卡岩型和热液脉型等锡铜矿化体,其形成时代是晚白垩世,属与花岗岩有关的岩浆热液成因矿床.赋存于三叠纪蚀变玄武岩层中,呈(似)层状的铜矿体的精确年龄尚未有报道,成因仍备受争议.文章选择赋存于卡房矿田蚀变玄武岩层中,呈(似)层状分布的铜矿体中的金云母,及新山岩体接触带云英岩中的白云母为研究对象,利用40Ar-39Ar阶段加热同位素定年方法对它们进行了年代学研究,获得了金云母和白云母的40Ar-39Ar同位素坪年龄分别为(79.55±0.47) Ma和(79.53±0.57) Ma,对应等时线年龄分别为(79.8±1.3)Ma和(79.7±1.0) Ma,反等时线年龄分别为(79.7±2.0) Ma和(79.61±0.75) Ma,两者年龄基本一致.结合矿物共生组合特征和流体包裹体测温资料,认为金云母的坪年龄(79.55±0.47) Ma,可以代表卡房蚀变玄武岩中(似)层状铜矿的形成时代,而白云母的坪年龄(79.53±0.57) Ma,则代表新山岩体形成后期岩浆热液活动的年龄.这2个年龄与个旧锡铜多金属矿床的成矿时代基本一致,应是同一构造-岩浆-流体活动形成的成矿系列产物.%The skarn type and hydrothermal vein type tin copper deposits in the Gejiu polymetallic tin copper ore district, formed in late Cretaceous, are referred to as the magmatic hydrothermal genesis. The stratified ore body, closely related to meta-basalt, has not been given accurate age, so there still exists controversy about its genesis. This paper presents new 40Ar-39Ar phlogopite age for the stratified ore body and muscovite age for the greisens from the contact zone of Xinshan granite intrusion in the Kafang tin-copper deposit so as to constrain the timing and duration of mineralization and the timing of the magmatic thermal activity after the formation of Xinshan granite body. Phlogopite and muscovite yielded 40Ar-39Ar plateau ages of (79.55 ± 0.47) Ma and (79.53 ± 0.57) Ma, isochronal ages of (79.8 ± 1.3) Ma and (79.7 ± 1.0) Ma, and inverse isochronal ages of (79.7 ± 2.0) Ma and (79.61 ±0.75) Ma. In combination with studies of mineral paragenesis and fluid inclusions, the authors have concluded that the 40Ar-39Ar system in phlogopite is closely related to ore deposition, and constrains the formation of the stratified ore body at (79.55 ± 0.47) Ma. The 40Ar-39Ar system in muscovite constrains the activity of the magmatic hydrothermal solution at (79.53 ± 0.57) Ma after the formation of Xinshan granite intrusion. These results are coincident with the data of the Gejiu polymetallic tin-copper deposits, and hence the above tin-copper deposits belong to the same structure-magma-fluid system.
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