大兴安岭南段内蒙古白音查干Sn多金属矿床石英斑岩的锆石U-Pb年龄、地球化学和Nd-Hf同位素特征及地质意义

发布时间：2018-07-05 04:30

本文选题：大兴安岭南段 + 白音查干Sn矿床　；参考：《岩石学报》2017年10期

【摘要】：白音查干矿床位于内蒙古自治区西乌珠穆沁旗,是大兴安岭南段新发现的一处大型Sn多金属矿床,也是该地区近些年来Sn矿找矿的重大突破。本文利用LA-ICP-MS锆石U-Pb法首次测得与成矿有关的石英斑岩成岩年龄为141.7±0.8Ma至140.2±1.1Ma。这一年龄与区内其他Sn多金属矿床成矿岩体的成岩年龄范围基本一致,说明大兴安岭南段与Sn成矿作用有关的花岗质岩石主要形成于早白垩世(140Ma左右)。全岩主量、微量和稀土元素地球化学特征显示,石英斑岩具有较高的SiO_2含量(70.99%~76.98%)、FeOT/(FeOT+MgO)值(0.90~0.97)、FeOT/MgO值(9.45~36.3)及10000×Ga/Al值(5.9~8.2)和较低的MgO(0.13%~0.18%)、TiO_2(0.10%~0.12%)及P2O5含量(0.02%~0.03%);稀土元素总量较低,配分模式呈轻稀土元素富集和明显负δEu异常的特点;微量元素富集Rb、U、Ta、Nd、Hf等元素,亏损Ba、K、Sr、P、Ti等元素。以上这些特征均说明,石英斑岩具备A型花岗岩的特点。微量元素、全岩Nd同位素和锆石Hf同位素结果显示,岩石具有较高的εNd(t)(+3.6~+3.8)和εHf(t)(+8.2~+11.6)值以及年轻的二阶段模式年龄(t_(NdDM2)为0.63~0.62Ga;t_(HfDM2)为0.67~0.45Ga),说明石英斑岩可能为幔源新生地壳物质部分熔融的产物,并在岩浆演化过程中经历了结晶分异作用。结合区域地质特征、成岩年代学、岩石地球化学和Nd-Hf同位素数据可知,大兴安岭南段晚中生代与Sn成矿作用有关的花岗岩以源区富含大量幔源新生地壳物质为特点,主要形成于晚中生代软流圈上涌所导致的岩石圈伸展的背景下。
[Abstract]:Baiyinchagan deposit is located in West Wuzhoumuqin Banner of Inner Mongolia Autonomous region. It is a large Sn polymetallic deposit newly discovered in the southern section of Daxing'an Mountains, and is also a major breakthrough in the prospecting of Sn deposits in this area in recent years. By using LA-ICP-MS zircon U-Pb method, the diagenetic ages of quartz porphyry related to mineralization are 141.7 卤0.8 Ma to 140.2 卤1.1 Ma for the first time. This age is basically consistent with that of other Sn polymetallic deposits in the area, indicating that granitic rocks related to Sn mineralization in the southern part of the Daxinganling Mountains were mainly formed in the early Cretaceous (about 140 Ma). The geochemical characteristics of total rock mass, trace amount and rare earth elements show that quartz porphyry has a higher SiOSt2 content (70.99g / 76.98%), Feot / (FeotMgO) value (0.900.97), Feot / MgO (9.45g / 36.3) and 10000 脳 Gap / Al (5.98.2) and lower MgO (0.130.18%), TiO2 (0.100.12%) and P2O5 (0.02o 0.03%), the total amount of REE is lower, The distribution pattern is characterized by light rare earth element enrichment and obvious negative 未 EU anomaly. These characteristics indicate that quartz porphyry has the characteristics of A-type granite. Trace elements, whole-rock ND isotopes and zircon HF isotopes show that, The rocks have higher 蔚 ND (t) (3.6-3.8) and 蔚 HF (t) (8.2 ~ 11.6) values and a young two-stage model age (t _ (NdDM2) is 0.63 ~ 0.62GafDM2 = 0.670.45Ga), which suggests that quartz porphyry may be the product of partial melting of mantle derived Cenozoic crustal material and undergo crystallization differentiation during magmatic evolution. Combined with regional geological characteristics, diagenetic geochronology, petrogeochemical and Nd-Hf isotopic data, the late Mesozoic granites associated with Sn mineralization in the southern Daxing'anling Mountains are characterized by a large amount of mantle derived Cenozoic crustal materials in the source area. It is mainly formed in the late Mesozoic lithospheric extension caused by the upwelling of the asthenosphere.
【作者单位】：中国地质调查局发展研究中心;中国地质大学地球科学与资源学院;国土资源部矿产勘查技术指导中心;西乌珠穆沁旗银漫矿业有限责任公司;中国地质科学院矿产资源研究所;
【基金】：国家重点研发计划(2017YFC0601506) 中国地质调查局项目(DD20160052、DD20160017)联合资助
【分类号】：P588.132;P618.2

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