Located in Zhongdian island arc belt in northwestern Yunnan Province, the Pulang super large porphyry copper deposit was formed in late Triassic during the westward subduction of the Ganzi-Litang ocean plate below Zhongdian microplate. The mineralized rocks of the Pulang porphyry copper deposit mainly include quartz dioritic porphyries and quartz monzonitic porphyries in a complex pluton, and economic ores are mainly preserved in the quartz monzonitic porphyries. The quartz dioritic porphyrites were intruded by later quartz monzonitic porphyries, but the two kinds of rocks display similar geochemical characteristics, such as similar REE patterns, incompatible trace element patterns and initial 87Sr/86Sr and Nd/144Nd ratios, suggesting that they were coge-netic products or were derived from similar sources. Geochemically, both kinds of rocks are akin to adakite, as evidenced by such characteristics as high Sr content (289×10-6~l 200×10-6), high La/Yb and Sr/Yb ratios, relatively high MgO and Mg# (>59), depleted Y and Yb, slightly negative Eu anomalies and positive Sranomalies Moreover, the radiogenic Sr [0.705 60 < (87 Sr/86 Sr)j < 0.705 74] and less radiogenic Nd [-2.8561.0%) and K2O (2.2%~4.4%), while the latter have high SiQ2(> 65.9%) and K2O (3.5%~8.1%). Therefore, the authors hold that the Pulang porphyry copper deposit was probably related to the westward subduction of Ganzhi-Litang oceanic plate during late Triassic. At the early stage of subduction, the quartz dioritic porphyries with subduction-related origin were formed firstly, then increasing adakitic magmas of slab melting were mixed with melts from subducted sediments or arc materials, producing more acid and high oxygen fugacity adakitic magmas, which finally intruded the upper crust below Pulang and promoted the mineralization of the Pulang porphyry copper deposit at the shallow level.%普朗斑岩铜矿床是中国西南“三江”地区新发现的具超大规模的印支期斑岩铜矿床,其成矿岩体的斑岩具有高的Sr含量(289×10-6～1 200×10-6,平均值为820×10-6)、Sr/Y(23～92)和La/Yb(平均值为16.4)比值和相对较高的MgO和M9#值(＞59),并富集大离子亲石元素和亏损高场强元素(Nb、Ta、Ti)等成分特征,这与形成于俯冲岛弧环境埃达克岩的地球化学组成相似,表明可能存在一个板片熔体在成岩和成矿过程中的贡献.同时高Th/Y、Ba/La、Rb/Sr和Ba/Sr比值,以及相对较高的(87 Sr/86 Sr)i同位素比值(0.70560～0.705 74)和较低的ε Nd(t)(-2.85～ -2.20),指示有一个富集组分参与了成矿斑岩的形成过程,这个富集组分可能是普朗地区的岛弧地壳基底物质,也可能是俯冲沉积物.岛弧地壳物质或俯冲沉积物、或两者与板片熔融的埃达克质熔体进行了一定程度的相互作用,导致成矿斑岩“混合”型地球化学的组成.初步提出,普朗斑岩铜矿床可能是在东侧的甘孜-理塘洋晚三叠世俯冲过程中形成的,俯冲作用在早期形成了具有岛弧成分特征的石英闪长玢岩,其后板片熔融形成的埃达克质熔体增加,并混合了一定数量的上覆地壳物质或沉积物,产生了更酸性的、并具有较高氧逸度的埃达克岩岩浆,上侵到普朗地区的地壳中形成成矿斑岩和相关的斑岩铜矿床.
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