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上黑龙江盆地虎拉林早白垩世岩体锆石U-Pb年代学、Hf同位素及地球化学特征研究
投稿时间:2019-05-20  修订日期:2019-09-21  点此下载全文
引用本文:
DOI:10.19762/j.cnki.dizhixuebao.2020152
摘要点击次数: 57
全文下载次数: 65
作者单位E-mail
巩 鑫 中国地质科学院矿产资源研究所 xingong2502@163.com 
赵元艺 中国地质科学院矿产资源研究所 E-mail:yuanyizhao2@sina.com 
水新芳 中国地质科学院矿产资源研究所  
程贤达 中国地质科学院矿产资源研究所  
王远超 中国地质科学院矿产资源研究所  
刘 璇 中国地质大学地球科学与资源学院  
谭 伟 中国地质大学地球科学与资源学院  
中文摘要:上黑龙江盆地虎拉林金矿床位于兴蒙造山带东段大兴安岭北部额尔古纳微地块北缘,夹持于蒙古-鄂霍茨克缝合带与得尔布干断裂之间,其矿体主要赋存于隐爆角砾岩中,与早白垩世岩浆活动形成的花岗斑岩、石英斑岩关系密切。本文采用LA-ICP-MS锆石U-Pb定年方法,获得花岗斑岩岩体结晶年龄为141.7±1.1Ma(MSWD=0.086)、石英斑岩(2件)岩体结晶年龄为144.9±0.56Ma(MSWD=0.580)和142.6±0.74Ma(MSWD=0.077),两者均为早白垩世岩浆活动产物。两岩体锆石?Hf(t)分别介于-4.14 ~ 0.16、-2.25 ~ 1.37,且大部分数据位于球粒陨石演化线之下,两阶段模式年龄(tDM2)分别为987.08 ~ 1259.04Ma、908.38 ~ 1138.56Ma。岩石地球化学特征显示,花岗斑岩w(SiO2)为66.21% ~ 66.70%,w(Al2O3)为15.18% ~ 15.45%,w(Na2O+K2O)为7.56% ~ 8.17%,铝饱和指数A/CNK为1.03 ~ 1.06,显示弱过铝质高钾钙碱性-钾玄岩序列;石英斑岩w(SiO2)为66.34% ~ 68.25%,w(Al2O3)为13.77% ~ 15.05%,w(Na2O+K2O)为6.76% ~ 9.06%,在SiO2-K2O图解中,落入钾玄岩序列范围内。花岗斑岩、石英斑岩ΣREE分别为71.07 ×10-6 ~ 97.92×10-6、135.53 ×10-6 ~ 156.15×10-6,(La/Yb)N分别为24.87 ~ 26.81、31.33 ~ 40.62,均表现轻稀土(LREE)相对富集、重稀土(HREE)相对亏损的右倾曲线特征,且轻、重稀土分馏明显;δEu分别为0.65 ~ 0.88、0.41 ~ 0.50,后者较前者铕负异常明显;两岩体均相对富集Rb、K等大离子亲石元素(LILEs)、LREE及U等不相容元素,强烈亏损Nb、Ta、Ti、P等高场强元素(HFSEs)。岩石成因类型判别图显示上黑龙江盆地虎拉林早白垩世侵入岩为I型花岗岩,形成于蒙古-中朝大陆与西伯利亚大陆后碰撞环境,由挤压转为伸展的构造背景下,可能是蒙古-鄂霍茨克造山带陆陆碰撞期间加厚古老地壳拆沉、部分熔融,并受到幔源物质或新生地壳熔融混染的产物,进而限制了蒙古-鄂霍茨克洋至少在144.9Ma以前已经完全闭合。
中文关键词:锆石U-Pb年代学  Hf同位素  地球化学  早白垩世  虎拉林  上黑龙江盆地
 
Zircon U-Pb chronology, Hf isotope and geochemical studies of the Early Cretaceous rocks in Hulalin of the Upper Heilongjiang basin
Author NameAffiliationE-mail
GONG Xin Institute of Mineral Resources,Chinese Academy of Geological Sciences xingong2502@163.com 
ZHAO Yuanyi Institute of Mineral Resources,Chinese Academy of Geological Sciences E-mail:yuanyizhao2@sina.com 
SHUI Xinfang Institute of Mineral Resources,Chinese Academy of Geological Sciences  
CHENG Xianda Institute of Mineral Resources, Chinese Academy of Geological Sciences  
WANG Yuanchao Institute of Mineral Resources, Chinese Academy of Geological Sciences  
LIU Xuan School of Earth Sciences and Resources, China University of Geosciences (Beijing)  
TAN Wei School of Earth Sciences and Resources,China University of Geosciences Beijing  
Abstract:The Hulalin gold deposit in the Upper Heilongjiang Basin is located in the northern margin of the Erguna micro-block in the northern Daxinganling, east of the Xingmeng orogenic belt, and is bounded between the Mongolian-Okhotsk suture zone and the Deerbugan fault. The orebodies occur mainly in the cryptoexplosive breccia, which is closely related to the granite porphyry and quartz porphyry formed by the Early Cretaceous magmatism. Using LA-ICP-MS zircon U-Pb dating method, this study obtained a crystallization age of 141.7±1.1Ma (MSWD=0.086) for granite porphyry, and two crystallization ages of 144.86±0.56Ma (MSWD=0.580) and 142.6±0.74Ma (MSWD=0.077) for two samples of quartz porphyry, both of which were products of early Cretaceous magma activity. The zircon ?Hf(t) values of granite porphyry and quartz porphyry are -4.14 ~ 0.16 and -2.25 ~ 1.37, and most of the data falls below the chondrite evolution line. The two-stage model ages (tDM2) of the two rocks are 987.08~1259.04 Ma and 908.38~1138.56Ma, respectively. The lithogeochemical characteristics show that the granite porphyry has w(SiO2) of 66.21% ~ 66.70%, w (Al2O3) of 15.18%~15.45%, and w(Na2O+K2O) of 7.56% ~ 8.17%, and aluminum saturation index A/CNK of 1.03~1.06, showing weak aluminum high potassium calc-alkaline-potassium rock series. Quartz porphyry has w(SiO2) of 66.34% ~ 68.25%, w(Al2O3) of 13.77% ~ 15.05%, and w(Na2O+K2O) of 6.76% ~ 9.06%, all of which fall in the potassium basalt area of the SiO2-K2O diagram. Granite porphyry and quartz porphyry has total REEs contents of 71.07×10-6~97.92×10-6 and 135.53×10-6~156.15×10-6 respectively, and (La/Yb)N of 24.87~26.81 and 31.33~40.62 respectively, all of which show the relative enrichment of LREE and the relative depletion of of HREE, with distinct fractionation of LREE and HREE. The both rocks have δEu values of 0.65 ~ 0.88 and 0.41 ~ 0.50 respectively, with the latter more abnormal than the former. Both rocks are relatively enriched in incompatible elements such as Rb, K and other large ion lithophile elements (LILEs), LREE and U, and strongly depleted in Nb, Ta, Ti, P and other high field strength elements (HFSEs). The petrogenetic discriminant diagram shows that the Early Cretaceous intrusive rocks of the Hulalin in the Upper Heilongjiang Basin are I-type granite, and formed in the post-collisional setting of Mongolia - China and North Korea continent and the Siberian continent. In such a tectonic setting of transition from compression to extension, the rocks formed from detachment and partial melting of thickened ancient crust due to the continent-continent collsion of Mongolia-Okhotsk orogenic belt, contaminated by mantle material or newly born crust. This further indicates that the Mongolian-Okhotsk ocean was closed completely before 144.9Ma at least.
keywords:zircon U-Pb chronology  Hf isotope  geochemistry  Early Cretaceous  Hulalin  Upper Heilongjiang basin
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