四川盐源西范坪斑岩铜矿石英二长斑岩锆石U-Pb同位素定年及其意义

发布时间：2019-01-27 07:37

【摘要】：四川盐源西范坪斑岩铜矿处于扬子地块西缘,靠近盐源-丽江坳陷带与甘孜-理塘缝合带的结合部位,该矿区侵入岩体主要为石英二长斑岩组成。西范坪铜矿石英二长斑岩LA-ICP-MS锆石U-Pb年龄为(100.8±0.7)Ma(MSWD=0.2),表明了斑岩侵位时代为早白垩世。石英二长斑岩富集大离子亲石元素(Rb、Ba、K),亏损高场强元素(Nb、Ta、Ti、P),LREE富集、HREE亏损,为高钾准铝质花岗岩。w(Si O2)为64.06%~65.24%,具有高w(Al_2O3)(15.58%~16.55%)、w(Sr)(719×10~(-6)~1221×10~(-6))及Sr/Y比值(49.2~82.5),低w(MgO)(1.30%~1.63%)、w(Yb)(1.08×10~(-6)~1.55×10~(-6))及w(Y)(13.7×10~(-6)~14.8×10~(-6)),Eu异常(0.83~0.90)不明显,轻重稀土分异明显((La/Yb)N=29.94~52.14),具有埃达克岩特征。西范坪埃达克岩富钾贫钠(K_2O/Na_2O=0.78~2.44),低Cr、Ni,高Th、Th/U以及相对低的Sr/Y等特征,表明其为加厚下地壳部分熔融形成。西范坪早白垩世(100.8Ma)地壳增厚作用可能受控于甘孜-理塘洋闭合后的造山运动,该斑岩体为印支期褶皱造山后(200 Ma),喜马拉雅期碰撞造山之前(65 Ma),陆内由挤压向伸展转换期岩浆作用的产物。
[Abstract]:The Xifangping porphyry copper deposit in Yanyuan, Sichuan is located in the western margin of the Yangtze block and is close to the joint site of the Yanyuan-Lijiang depression belt and the Ganzi-Litang suture zone. The intrusive rock mass of the mine is mainly composed of quartz monzonitic porphyry. The LA-ICP-MS zircon U-Pb age of Yingerpeng porphyry from Xifangping copper ore is (100.8 卤0.7) Ma (MSWD=0.2), indicating that the porphyry emplacement was early Cretaceous. Quartz monzomorphic porphyry is rich in large ion lithophile elements (Rb,Ba,K), depleted high field strength elements (Nb,Ta,Ti,P), LREE enrichment, HREE depletion, high potassium pseudoaluminous granite. W (Si O2), and is 64.06% 65.24%. High w (Al_2O3) (15.58%), w (Sr) (719 脳 10 ~ (-6) ~ 1221 脳 10 ~ (-6) and Sr/Y ratio (49.2%), low w (MgO) (1.30% (1.63%), W (Yb) (1.08 脳 10 ~ (-6) ~ 1.55 脳 10 ~ (-6) and w (Y) (13.7 脳 10 ~ (-6) ~ 14.8 脳 10 ~ (-6), Eu anomaly (0.83 ~ (-6) 0.90) were not obvious, and the difference of light and heavy rare earth elements (La/Yb) was obvious (La/Yb) N ~ (29. 94) ~ (52.14). It has the characteristics of adakite. It is characterized by rich potassium and poor sodium (K_2O/Na_2O=0.78~2.44), low Cr,Ni, high Th,Th/U and relatively low Sr/Y in Xifangping Adakite, which indicates that it is formed by partial melting of thickened lower crust. The crustal thickening of the early Cretaceous (100.8Ma) in Xifangping may be controlled by the orogenic movement after the closure of the Ganzi-Litang Ocean, which occurred after the Indosinian fold orogeny (200 Ma), before the collision orogeny of the Himalayas) (65 Ma),). The product of magmatism during the transition from compressional to extensional within the continent.
【作者单位】：成都地质矿产研究所;
【基金】：中国地质调查局地质调查项目(DD20160016;12120113036500)
【分类号】：P597.3;P618.41

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