北武夷塘里矿区侵入岩岩石学特征及其成因探讨

发布时间：2018-03-12 06:49

本文选题：侵入岩　切入点：岩石成因　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：位于武夷造山带北缘的梨子坑火山盆地,近年来发现了许多铜铅锌多金属矿床,显示出了良好的找矿潜力。然而关于区内岩石成因和区域构造背景的研究一直存在许多争论。塘里矿区位于梨子坑火山盆地的西北缘,区内盆地边缘发育的侵入岩体是对燕山期洋陆会聚过程中构造性质的重要岩石记录。因此,本论文选择塘里矿区侵入岩体为研究对象,结合岩石组合类型,地球化学和Sr-Nd-Pb同位素分析,讨论了其岩石成因及其动力学背景。(1)经过岩相学和岩石地球化学的研究,厘定了塘里矿区侵入体主要为黑云母石英二长岩和花岗斑岩,两者具有相似的演化特征,为同期岩浆作用的产物。本次利用LA-MC-ICPMS锆石U-Pb测定了两个样品年龄,结果显示其成岩年龄为138.02±0.49Ma和138.7±1.2 Ma,均为早白垩世,燕山晚期的侵入体。(2)黑云母石英二长岩SiO_2含量变化于63.25~65.44%,Al2O3含量在16.44~17.31%之间,Fe、Mg含量较低,全碱含量变化于9.22~9.65%,K2O/Na2O比值为1.76~2.09,A/CNK在1.04~1.19之间。花岗斑岩SiO_2含量变化于71.75~74.79%,Al2O3含量在12.56~13.70%之间,全碱含量变化于8.31~9.45%,K2O/Na2O比值为1.76~2.09,A/CNK在1.47~2.40之间,两者均具高钾、富碱、低铁镁、偏铝质-过铝质的特征,属高钾钙碱性-钾玄岩系列火成岩。(3)塘里矿区侵入岩稀土总量较高,轻重稀土分馏明显,Eu负异常,稀土配分模式呈轻稀土富集的右倾型。富集大离子亲石元素Rb、Th、Pb,亏损高场强元素Ba、Nb、Ta、P、Ti,无明显的Ce异常。ISr平均0.7091,εNd(t)为-10.49~-7.59,Nd的二阶段模式年龄约为1.7Ga,(206Pb/204Pb)i为18.010,(207Pb/204Pb)i为15.587,(208Pb/204Pb)i为38.479,为“I”型向“S”型过渡的花岗岩。(4)塘里矿区侵入岩构造背景为燕山期的洋陆汇聚,古太平洋板块俯冲,地幔楔物质受热形成玄武质岩浆,地幔岩浆反复底侵并滞留下地壳形成钙碱性岩浆,随后又引起下地壳部分熔融产生高钾钙碱性的花岗岩浆,成岩物质应以中元古代地层部分熔融为主,岩浆上侵过程受到一定程度混染。区内早白垩世侵入岩可能形成于燕山期大陆边缘弧环境。
[Abstract]:In recent years, many copper-lead-zinc polymetallic deposits have been discovered in the Lizikeng volcanic basin, located in the northern margin of the Wuyi orogenic belt. It has shown good prospecting potential. However, there have been many controversies about the petrogenesis and the regional tectonic setting in the area. The Tangli mining area is located on the northwest margin of the Lizikeng volcanic basin. The intrusive rock mass developed on the margin of the basin is an important rock record of the tectonic properties of the Yanshanian oceanic land convergence process. Therefore, the intrusive rock mass in Tangli mining area is selected as the research object, combining with the rock assemblage type. Geochemistry and Sr-Nd-Pb isotopic analysis, its petrogenesis and its dynamic background. (1) based on the study of petrography and petrochemistry, it is determined that the intrusions in Tangli ore area are mainly biotite quartz monosite and granitic porphyry. Both of them have similar evolution characteristics and are the product of contemporaneous magmatism. Two samples ages were determined by LA-MC-ICPMS zircon U-Pb. The results show that their diagenetic ages are 138.02 卤0.49 Ma and 138.7 卤1.2 Ma, both of which are early Cretaceous. During the late Yanshanian period, the SiO_2 content of biotite quartz monzonite changed from 63.25 to 65.440.The content of Al _ 2O _ 3 was between 16.44 and 17.31%, and the total alkali content varied from 9.22 to 9.65% K _ 2O / Na _ 2O _ 2O ratio of 1.762.09 A / C _ (1. 19). The content of SiO_2 in granitic porphyry changed from 12.560.13.70% to 13.70%. The total alkali content varied from 8.31 to 9.45% and the ratio of K _ 2O / Na _ 2O to K _ 2O / Na _ 2O was 1.760.2.09A / CNK was 1.472.40. Both of them had the characteristics of high potassium, alkali rich, low iron and magnesium, mesialuminum-peraluminous, belonging to the series of igneous rock. 3) the total amount of rare earth in the Tangli mine was higher than that in the Tangli mine, which was characterized by high potassium, alkali, low iron and magnesium, and metaaluminum-peraluminous. The fractionation of light and heavy rare earths shows negative EU anomalies. The REE partitioning pattern shows a right dip pattern of LREE enrichment. The enrichment of large ion lipophilic element RbPb, the depletion of high field strength element BaNbPnb, the absence of obvious ce anomaly, the average of 0.7091, 蔚 Ndnt is -10.49- 7.59ND, the two-stage model age is about 1.7GaGa-206Pb204PbBNI = 18.010107Pb204Pbnnnbngt = 15.587nb208Pb204Pbnnnbnnteri = 38.479, "I type" S = "S" = "I" = "S" = 38.479p / r = -10.49% -7.599 ND = -10.49% -7.599 ND. The tectonic setting of intrusive rocks in Tangli ore area is Yanshanian oceanic convergence. The paleo-Pacific plate subducted, the mantle wedge material heated to form Black Tortoise magma, the mantle magma repeatedly underpenetrated and stayed in the lower crust to form calc-alkaline magma, and then caused partial melting of the lower crust to produce high-potassium calc-alkaline granite magma. The diagenetic material should be partially melted in the Mesoproterozoic strata and the magmatic intrusion process is mixed to some extent. The early Cretaceous intrusive rocks in this area may have been formed in the Yanshanian continental margin arc environment.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.12;P612

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