东昆仑野马泉铁矿相关花岗质岩体年代学、地球化学及Hf同位素特征

Geochronology,geochemistry and Hf isotopic compositions of the granitic rocks related with iron mineralization in Yemaquan deposit,East Kunlun,NW China

野马泉大型铁多金属矿床位于东昆仑造山带祁漫塔格地区，矿区发育大量与铁多金属成矿关系密切的花岗质岩体。LA-ICP-MS锆石U-Pb定年表明北矿带隐伏二长花岗岩、花岗闪长岩年龄分别为3934±2Ma、386±1Ma；南矿带斑状石英二长闪长岩、正长花岗岩年龄为219±1Ma、213±1Ma，分别为早-中泥盆世和晚三叠世岩浆活动的产物。早一中泥盆世花岗闪长岩与二长花岗岩均为高钾钙碱性，A／CNK值（0．92～1．01）〈1．1，具中等强度的负Eu异常（δEu为O．60～0．81），明显亏损P、Nb、Ta、Ti、Sr、Ba等，富集LREE、Rb、Th、U、K等，显示了I型花岗岩的特征。晚三叠世斑状石英二长闪长岩含有少量角闪石，A／CNK值（0．88—0．95）〈1，轻稀土富集，具中等负Eu异常（8Eu为0．49～0．67），富集Rb、U、Th、K等大离子亲石元素，亏损P、Nb、Ta、Ti、Sr、Ba等，具有I型花岗岩的特征；正长花岗岩高硅（Si02=77．20％～78．13％）、富碱（K20＋Na20=7．91％～8．27％）、贫铝（A1203=11．71％～12．18％）、贫钙（CaO=0．90％～1．01％），富集LREE、Y、Zr、Hf、rI＇Il、u、Ga等，强烈亏损Ba、Sr、P、Ti、Eu，具强烈的负Eu异常（SEu为0．08—0．13），显示弱过铝质A型花岗岩的特征。锆石I-If同位素组成表明，早．中二叠世岩体的εHf（t）为-3．3—6．2，晚三叠世岩体的εHf（t）为-6．3—5．5，显示在成岩过程中有地幔组分的参与。综合研究认为，野马泉矿区早-中泥盆世、晚三叠世岩体分别形成于早古生代构造-岩浆旋回的碰撞．后碰撞阶段和晚古生代．旱中生代构造-岩浆旋回的碰撞-后碰撞阶段，可能是由地幔底侵古老陆壳，幔源基性岩浆与壳源花岗质岩浆发生不同程度混合作用而生成，壳幔物质交换为区内大规模铁铜铅锌多金属矿化提供大量成矿物质。

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 restdts of LA-ICP-MS zircon U-Pb isotope dating reveal that monzogranite an, granodiorite in the north ore district were formed in 393 ± 2Ma and 386 ± 1Ma respectively, while porphyritic quartz monzonitic diorit, and syenogranite in the south ore district were formed in 219 ± 1Ma and 213 ± 1Ma respectively. Major and trace dement data of th, 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 （δEu =0.60 ~0.81）, depleted in P, Nb, Ta, Ti, Sr and Ba, enriched il LREE, Rb, Th, U and K, all of which imply they may be the I-type granite series. The Late Triassic porphyritic quartz monzonit, diorites are I-type granites, characterized by A/CNK （0. 88 -0. 95） 〈 1, LREE enrichment, medium to strong negative Eu anomali~ （SEu = 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 （ K20 ＋ Na2O =7. 91% ~ 8.27% ）, low Al2O3 （11.71% -12. 18% ）, low CaO （0. 90% ~1.01% ）, enriched in LREE, Y, Zr, I-If, 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 sm（t） values of Latt Triassic syenogranite and porphyritic quartz monzonitic diorite range from - 6. 3 to 5.5. The similar Hf isotopic compositions indicate 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 tc Early Mesozoic collision-post collision stage respectively. The magma mixing provides a large number of ore-forming materials for large. scale polymetallic mineralizations.