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青藏高原南部发育有大规模的碰撞成矿作用,冈底斯北缘Pb-Zn-Ag-Cu-Fe多金属成矿带是其重要的组成部分。加拉普铁矿床是位于该成矿带东侧的矽卡岩型铁矿床,其成矿作用与区内的花岗闪长岩有密切的成因联系。LA-ICP-MS锆石U-Pb定年结果显示,该岩体成岩年龄为(63·4±0·5)Ma(n=25,MSWD=1·2),表明矿床形成于印-亚陆陆碰撞的主碰撞阶段。地球化学研究结果显示,岩石属中-高钾钙碱性准铝质花岗岩;其ΣREE较低(100·5×10-6～170·3×10-6),具弱-中等负Eu异常,富集轻稀土元素(LREE),相对亏损重稀土元素(HREE);富集大离子亲石元素(LILE)Rb、Pb、K、Th,相对亏损高场强元素(HFSE)Hf、Ta、Ti、Nb等,与早期的林子宗火山岩相类似,具有弧火山岩的地球化学特点。岩石εNd(t)值为-2·60～-2·34,(87Sr/86Sr)初始值为0·7074～0·7075,反映了重熔地壳物质与幔源物质混合的特点。锆石Lu-Hf同位素测试结果显示,岩体的锆石εHf(t)值和地壳模式年龄均分布较广,分别为-9·1～4·3和864～2368Ma,同样表明岩石岩浆源区具有壳幔混源的特征。综合上述数据,矿区的花岗闪长岩是地幔源区岩浆与陆壳重熔岩浆混合而成的壳幔混源的I型花岗岩。已有数据显示,冈底斯北缘Pb-Zn-Ag-Cu-Fe多金属成矿带从白垩纪至中新世均有强烈的成矿作用,但其主成矿期集中在62～50Ma,且与主碰撞阶段的岩浆活动有密切的成因联系。Pb-Zn-Ag成矿作用主要与受壳源物质控制的花岗岩密切相关,而与Fe-Cu矿化有关的岩体则更多地显示了幔源物质的贡献。
Large-scale collision and mineralization develop in the southern part of the Qinghai-Tibet Plateau. Pb-Zn-Ag-Cu-Fe polymetallic metallogenic belt in the northern margin of the Gangdese is an important component. The Galapu iron deposit is a skarn type iron deposit located on the eastern side of the metallogenic belt. Its mineralization is closely related to the granodiorite in the area. The zircon U-Pb dating of LA-ICP-MS shows that the diagenetic age of this rock is (63.4 ± 0.5) Ma (n = 25, MSWD = 1.2), indicating that the deposit was formed in Indo- Land collision of the main collision stage. The results of geochemistry show that the rocks are medium-high-K calc-alkaline quasi-aluminous granites with low ΣREE (100 · 5 × 10-6 ~ 170 · 3 × 10-6), weak-moderate negative Eu anomalies, Enriched LREE and relatively depleted heavy rare earth elements (HREEs); enriched LILEs Rb, Pb, K, Th relative depleted high field strength elements (HFSE) Hf, Ta, Ti , Nb, etc., similar to the early Linzizong volcanic rocks, have the geochemical characteristics of arc volcanic rocks. The εNd (t) values of rock range from -2.60 to -2.34 and the initial values of (87Sr / 86Sr) range from 0.7074 to 0.7075, reflecting the mixing of remelted crustal material with mantle materials. The zircon Lu-Hf isotope test results show that the zircon εHf (t) value and the crustal model age of the rock mass are widely distributed, ranging from -9.1 to 4.3 and 864 to 2368Ma, respectively, indicating that the rock magma source area With crust and mantle mixed source features. Based on the above data, the granodiorite in the mining area is a type I granite derived from crust-mantle mixed source formed by mixing mantle-derived magma with continental remelting magma. The available data show that the Pb-Zn-Ag-Cu-Fe polymetallic metallogenic belt in the northern margin of the Gangdese has a strong mineralization from the Cretaceous to the Miocene. However, its main mineralization period is concentrated at 62 ~ 50Ma , And is closely related to the magmatic activity in the main collision stage. The Pb-Zn-Ag mineralization is mainly related to the granite controlled by the crust-source material, while the rock mass related to the Fe-Cu mineralization shows more the contribution of the mantle-derived material.