摘要
应用LA-ICP-MS对马厂箐岩体中(似)斑状花岗岩的锆石进行了U-Pb定年和微量元素分析。在CL图像上,(似)斑状花岗岩中锆石均发育有典型的振荡环带,锆石的稀土元素配分模式表现为亏损轻稀土,富集重稀土,具有强烈正Ce异常和中度负Eu异常,且呈现出较高的Th/U比值等特征,表明所测锆石均为典型的岩浆锆石。马厂箐岩体(似)斑状花岗岩锆石U-Pb加权平均年龄为(33.78±0.21)Ma(MSWD=0.71),累计概率统计得到正长斑岩锆石U-Th-Pb年龄为(35.6±0.3)Ma、花岗斑岩锆石U-Th-Pb年龄为(35.0±0.2)Ma,宝兴厂矿段铜钼矿辉钼矿Re-Os等时线年龄分别为(35.8±1.6)Ma和(33.9±1.1)Ma,乱硐山矿段接触交代型金矿白云母40Ar/39Ar年龄为(35.25±0.36)Ma,人头箐—金厂箐矿段热液脉型金成矿白云母40Ar/39Ar年龄为(35.35±0.32)Ma,反映斑岩型铜钼矿化、接触交代型金矿化和热液脉型金矿化为同一个构造-岩浆-热液成矿系统的产物,Ⅱ期(33～37Ma)正长斑岩+二长斑岩+花岗斑岩+(似)斑状花岗岩岩性组合是成矿的地质体,为成矿提供了物质、流体和热动力条件,这期斑岩-热液-成矿系统的持续时间约为4Ma,铜、钼、金的成矿主要发生在Ⅱ期岩浆活动的早-中期。
U-Pb ages and trace elements of zircons from porphyritic granite of Machangqing complex were analyzed by the LA-ICP-MS method.As revealed by the cathodoluminescence（CL） images,all the zircons from porphyritic granite have the oscillatory zoning.REE patterns of the analyzed zircons are characterized by significantly high heavy rare earth elements（HREE）,depleted light rare earth elements（LREE）,obviously positive Ce anomaly and moderately negative Eu anomaly.In addition,nearly all the zircons have high Th/U ratios.These characteristics suggest a magmatic genesis of the analyzed zircons.The zircons from the porphyritic granite of Machangqing complex yield the U-Pb weighted average age of（33.78±0.21）Ma（MSWD=0.71）,whereas zircons from syenite porphyry and granitic porphyry yield the U-Th-Pb ages of（35.6±0.3）Ma and（35.0±0.2）Ma by cumulative probability statistics.Molybdenites from the Baoxingchang ore block yield the Re-Os isochron ages of（35.8±1.6）Ma and（33.9±1.1）Ma.Muscovites of contact metasomatic gold mineralization from the Luandongshan ore block yield the 40Ar/39Ar age of（35.25±0.36）Ma.Muscovites of hydrothermal vein gold mineralization from the Rentouqin-Jinchangqin ore block yield the 40Ar/39Ar age of（35.35 ±0.32）Ma.These ages show that porphyry type copper-molybdenum mineralization,contact metasomatic gold mineralization and hydrothermal vein gold mineralization are products of the same tectonic-magmatic-hydrothermal ore-forming system,and that theⅡperiod magmatic combination（33～37 Ma） of syenite porphyry＋monozonite porphyry＋granitic porphyry＋ porphyritic granite seems to have been the ore-forming geological body,which supplied materials,fluid and thermodynamic conditions for the ore-forming process.The duration of the porphyry-hydrothermal fluid-ore forming system is about 4 Ma.The ore-forming process of copper,molybdenum and gold occurred in the early-middle stage.
出处
《中国地质》
CAS
CSCD
北大核心
2011年第3期610-622,共13页
Geology in China
基金
973国家重点基础研究发展计划(2009CB421000)
武警黄金指挥部专项基金(HJ09-03)资助
