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Gao Y.B.,Genesis Centre | Gao Y.B.,Changan University | Li W.Y.,Genesis Centre | Qian B.,Genesis Centre | And 6 more authors.
Acta Petrologica Sinica

The large-scale Yemaquan iron polymetallic deposit is located in Qimantage, East Kunlun, and the granitic rocks are closely related with iron polymetallic mineralization. The results of LA-ICP-MS zircon U-Pb isotope dating reveal that monzogranite and granodiorite in the north ore district were formed in 393 ±2Ma and 386 ± IMa respectively, while porphyritic quartz monzonitic diorite and syenogranite in the south ore district were formed in 219 ± IMa and 213 ± IMa respectively. Major and trace element data of the Early-Middle Devonian monzogranite and granodiorite show the similar characteristics, with high K calc-alkaline, A/CNK (0. 92 ∼ 1. 01) < 1. 1, medium to strong negative Eu anomalies (<5Eu = 0. 60 ∼ 0. 81), depleted in P, Nb, Ta, Ti, Sr and Ba, enriched in LREE, Rb, Th, U and K, all of which imply they may be the I-type granite series. The Late Triassic porphyritic quartz monzonite diorites are I-type granites, characterized by A/CNK (0. 88 ∼0. 95) < 1, LREE enrichment, medium to strong negative Eu anomalies (δ5Eu = 0. 49 ∼ 0. 67), rich LILEs such as Rb, U, Th and K, depleted HFSEs such as P, Nb, Ta, Ti, Sr and Ba. Chemical analyses show the Late Triassic syenogranite has high SiO2(77. 20% ∼78. 13%), high alkaline (K2O + Na2O =7. 91% ∼8.27%), low A12O 3 (11.71% ∼12. 18%), low CaO (0.90% ∼1.01%), enriched in LREE, Y, Zr, Hf, Th, U and Ga, depleted in Ba, Sr, P, Ti, Eu, strong negative Eu anomalies (δEu =0.08-0. 13). These characteristics suggest the syenogranites are typical A-type granites. The εHF(t) values of the Early-Middle Devonian monzogranite and granodiorite vary from -3. 3 to 6. 2, and the εHT(t) values of Late Triassic syenogranite and porphyritic quartz monzonitic diorite range from - 6. 3 to 5. 5. The similar Hf isotopic compositions indicate a significiant involvement of mantle components in petrogenesis. It is suggested that the Early-Middle Devonian and Late Triassic magmatic rocks in Yemaquan deposit might be formed by underplating and magma mixing in the Early Paleozoic and Late Paleozoic to Early Mesozoic collision-post collision stage respectively. The magma mixing provides a large number of ore-forming materials for largescale polymetallic mineralizations. Source

Li K.,Genesis Centre | Gao Y.-B.,Genesis Centre | Qian B.,Genesis Centre | He S.-Y.,No 3 Geological Prospecting Institute Of Qinghai | And 4 more authors.
Geology in China

The Hutouya Pb-Zn polymetallic ore deposit is located in Qimantag, East Kunlun. Intermediate-acid intrusive rocks occur widely in this area, and are closely related to iron polymetallic mineralization. The results of LA-ICP-MS zircon U-Pb isotope dating reval that the granodiorite in the periphery of No. Vore belt was formed at (224.3±0.6) Ma and the orthoclase granite in No. VIII ore belt was formed at (239.7±0.8) Ma. Petrogeochemistry shows that the granodiorite is rich in K and poor in Na, with no strong negative Eu anomalies (δEu=0.68-1.06), and is enriched in Rb, Th, U, K, but depleted in Nb, P, Ti, thus belonging probably to I-type granite series. The orthoclase granite is characterized by high SiO2, high alkali, low TFeO, MgO, CaO, P2O5 and TiO2, strong negative Eu anomalies (δEu 0.08-0.26), enrichment of Rb, Th, U, K, and depletion of P, Ti, Ba, Sr, belonging probably to highly fractionated I-type granite series. Both of them were formed at the post-collision stage. Variable Hf isotopic compositions of zircon indicate that it experienced magma mixing, which provided large quantities of ore-forming meterials for large-scale polymetallic mineralization. Source

Li D.-S.,Queens University | Su S.-S.,No 3 Geological Prospecting Institute Of Qinghai | Zhang C.-G.,Queens University | Zhang D.-M.,No 3 Geological Prospecting Institute Of Qinghai | Wang S.-M.,No 3 Geological Prospecting Institute Of Qinghai
Geology in China

The porphyritoid dioritic enclaves are widely distributed in granodiorites of the Kaerqueka copper deposit, East Kunlun belt. The enclaves are mostly aligned ovals, with similar mineralogy to the host rocks. However, the modal percentage of hornblende is significantly higher than that of the host rock. It has apparent imbalanced structure with development of needle-like apatite. The granodiorite and enclaves have the same age of 234 Ma, which indicates that they might have been formed by magma mixing. As for geochemical characteristics, the enclaves contain higher values of SiO2 and MgO than the host rock and are hence more mafic. They are also enriched in large LILE and LREE, and are depleted in HFSE. The LaN/YbN ratios of host granodiorite (11.6-19.0) are significantly higher than the ratios of the enclaves (5.0-9.7). The Nb/Ta values of host granodiorite (10.6-11.7) are lower than those of the enclaves (11.6-14.8). They have similar Sr, Nd and Hf isotopic compositions. The granodiorite has εnd(t) values of-5.3 to -4.2, (87Sr/86Sr)i values of 0.71110-0.71125, εHI(t) values of-5.8 to -1.6, tDM(Hf) values of 1012-1102 Ma. The enclaves have εNd(t) values of-5.2 to -5.0, (87Sr/86Sr)i values of 0.71114-0.71171, εHI(t) values of-6.3 to -3.4, and tDM(Hf) values of 937-1129 Ma. These data indicate that, at the subduction-collision transition stage of Triassic period, the enriched EMII type lithosphere mantle underwent partial melting and produced mafic magma under the influence of upwelling asthenosphere materials. The partial melting of lower crust materials, which had been underplated by the mantle, formed the felsic magma chamber. The injection of mafic magma into the felsic magma chamber formed enclaves. After mixing of evolved mafic magma with felsic magma, enclaves-bearing homogeneous magma was formed. The crystallization of this homogeneous magma formed granodiorites containing enclaves. Source

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