波龙铜矿区成矿斑岩同位素对岩浆源区的限制

为了查明波龙铜矿区成矿花岗闪长斑岩的岩浆源区,系统地测试了斑岩的Sr-Nd-Pb同位素。结果表明,成矿花岗闪长斑岩的δ87Rb/δ86Sr为1.265~10.151 2,δ87Sr/δ86Sr为0.711 041~0.725 101,(δ87Sr/δ86Sr)i为0.707 59~0.709 83;δ143Nd/δ144Nd为0.512 09~0.512 30,εNd(t)变化范围为-7.714 774~-3.572 778;δ206Pb/δ204Pb为17.068~17.820,δ207Pb/δ204Pb变化范围为15.485~15.556,δ208Pb/δ204Pb为36.861~37.804。Sr-Nd-Pb同位素特征表明,波龙成矿斑岩的岩浆源区具有EMⅠ型富集地幔与EMⅡ型富集地幔的特征,起源于洋壳俯冲脱水形成的流体交代楔形地幔区,并在上侵过程中受到了下地壳物质的混染。波龙铜矿床形成于班公湖—怒江洋向北俯冲诱发的岩浆作用过程中。

Restriction of Mineralization of Porphyry Isotopes to Magma Source Area in Bolong Copper Mine Area

In order to identify the magma source of the Bolong metallogenic granodiorite porphyry,the Sr-Nd-Pb isotopes of the metallogenic granodiorite porphyry are tested systematically.The test results show that,the values of δ⁸⁷Rb/δ⁸⁶Sr and δ⁸⁷Sr/δ⁸⁶Sr are from 1.265 to 10.151 2 and from 0.711 041 to 0.725 101，and the value of (87Sr/86Sr)i is from 0.707 59 to 0.709 83.The value of (¹⁴³Nd/¹⁴⁴Nd)i and ε_Nd(t) are from 0.512 09 to 0.512 30 and from -7.714 774 to -3.572 778 respectively.And the ranges of δ²⁰⁶Pb/δ²⁰⁴Pb,δ²⁰⁷Pb/δ²⁰⁴Pb and δ²⁰⁸Pb/δ²⁰⁴Pb are from 17.068 to 17.820,from 15.485 to 15.556,and from 36.861 to 37.804 correspondingly.The characteristics of Sr-Nd-Pb isotope shows that,the magma source of the Bolong copper mine area owns the property of EMⅠ and EMⅡ type enriched mantle and it may have originated from the mantle fluid metasomatism wedge area formed by the oceanic curst subduction dehydration,and been contaminated by the lower crust mass in the process of invasion.The Bolong porphyry copper deposit is formed in the magmatism process induced with the northward subduction of the Bangong Lake Neo-Tethyan Ocean.