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1.
The Geza Andean-type arc is located in the southwestern Sanjiang tectonic belt (i.e. Jinsha, Lancang, and Nujiang River) of SW China, which is a product of the subduction of the Garzê–Litang oceanic crust beneath Zhongdian landmasses in the Late Triassic (235–204 Ma). The Geza Andean-type arc is an important belt of Cu-rich polymetallic mineralization that was recently discovered in China. Prolonged regional tectono-magmatic activity and several episodes of rich mineralization throughout the tectonic evolution of the Andean-type arc produced the super-large Pulang porphyry Cu deposits, the large Xuejiping porphyry Cu deposits, and the large Hongshan skarn-porphyry Cu polymetallic deposits. Here we report new LA-ICP-MS zircon U–Pb age of Songnuo and Qiansui intrusive rocks, and whole-rock major and trace element compositions of the Late Triassic mineralized porphyries from Geza in this region. Zircon U–Pb dating of the Qiansui quartz diorite porphyrite revealed a crystallization age of 220.3 ± 0.66 Ma, for the Songnuo quartz monzonite porphyry, a crystallization age of 204.7 ± 0.72 Ma. The Geza Andean-type arc granitic belt can be divided into three porphyry subzones based on the stage of Andean-type arc orogenic development and the distribution, composition, and geochemical characteristics of the intrusive rocks. Lithogeochemical characteristics show that the porphyry and Andean-type arc granite are of the same rock series (high-K calc-alkaline) and genetic type (I-type granite). The trace element geochemistry of these rocks is similar to that of Andean-type arc granite, which is enriched in Ba, Rb, La, Hf, chalcophile elements (Cu, Pb), and siderophile elements (Mo, Ni), and depleted in Nb, Ta, P, and Ti. In the Geza Andean-type arc, similarities in the major element, REE, and trace element compositions between porphyry and local acidic volcanic rocks suggest that they have the same or similar magmatic source rocks. The petrological characteristics of granite in the Geza Andean-type arc are similar to those of adakitic rocks, and the formation of porphyry and porphyry-related deposits resulted from magmatic hydrothermal fluids that originated in the upper mantle and lower crust. The porphyry Cu mineralization was probably produced from the accumulation and migration of ore-forming hydrothermal fluids and the resultant alteration of host rocks. 相似文献
2.
秦祁昆结合部瓦勒根金矿床含矿斑岩体岩石学和LA-ICP-MS锆石U-Pb年龄 总被引：1，自引：0，他引：1
秦祁昆结合部广泛发育中三叠世岛弧钙碱性岩浆作用,已发现大量与其相关的斑岩型—夕卡岩型铜金、铜钼和银铅锌多金属矿床。瓦勒根金矿床是近年来在该区新发现的一个斑岩型金矿床,矿区内出露有众多的石英斑岩和花岗斑岩,且均发育有金矿化,其中石英斑岩与金矿化关系更为密切。LA-ICP-MS锆石U-Pb年龄表明,花岗斑岩形成于中三叠世(237Ma),其中包含有丰富的晚古生代及元古宙继承性锆石。这一特征与区域上的斑岩型铜金矿床含矿岩体具有相似性。进一步说明,古特提斯洋在秦祁昆结合部发生向北消减所形成的岩浆捕获了早于三叠纪的壳源和幔源物质,从而形成了岛弧钙碱性岩浆及相关的斑岩型—夕卡岩型矿床组合。 相似文献
3.
跃进山小型矽卡岩型铜金矿床位于完达山地体西南部,矿体主要赋存于矽卡岩、花岗斑岩及其构造裂隙中,呈扁豆状或脉状。本文对矿区花岗闪长岩和花岗斑岩进行锆石U-Pb年代学和岩石地球化学研究,以了解矿床形成时代、成岩（矿）构造背景及矿床成因。测年结果表明,花岗斑岩和花岗闪长岩成岩年龄分别为（115.8±1.0）Ma和（126.9±1.7）Ma,铜金矿化时代与花岗斑岩成岩时代基本一致,为早白垩世晚期。岩石地球化学研究表明,花岗闪长岩属过铝质钙碱性系列岩石,稀土配分模式图为轻稀土富集,重稀土亏损,具较强的铕负异常,无铈异常,岩浆主要来源于壳源物质;花岗斑岩属过铝质钙碱性系列岩石,轻稀土富集,重稀土亏损,具弱铕负异常,无铈异常,相对富集大离子亲石元素（Rb、Ba、K、Sr）和不相容元素（U、Th）,亏损高场强元素（Ta、Nb、P、Ti）和HREE,岩浆来源于壳幔物质混合源区,形成于碰撞后构造环境,成岩成矿作用与太平洋板块强烈俯冲作用后的伸展体制密切相关。 相似文献
4.
青海乌兰县赛坝沟金矿床位于柴北缘结合带东部,为一中型石英脉型金矿。为进一步确定该矿床形成年龄和成因,对矿区内与成矿关系密切的花岗斑岩脉进行锆石U-Pb年代学和岩石地球化学研究。花岗斑岩LA-ICP-MS锆石U-Pb年龄为(372.4±4.1) Ma,是晚泥盆世岩浆活动的产物。花岗斑岩具高硅、富碱的特征,分异指数(DI)为81.40~84.54,固结指数(SI)为3.56~8.17,表明岩石结晶分异程度较高;微量元素原始地幔标准化图解显示La、Hf、Rb、Th相对富集,而Nb、Ta、P、Ti、Ba、Sr相对亏损;稀土元素球粒陨石标准化配分曲线呈右倾的轻稀土元素富集型,且具轻微Eu元素负异常。综合判别图解分析,认为花岗斑岩属过铝质钙碱性的I型花岗岩。赛坝沟金矿床花岗斑岩形成时间与柴北缘中晚泥盆世陆内伸展时间一致,整体形成于柴北缘中晚泥盆世陆内伸展阶段的后造山构造环境中。脉岩紧邻矿体产出并充填在构造裂隙中,其形成与成矿年龄相接近,因此可将赛坝沟金矿形成时间上限限定在372.4 Ma。后期找矿勘查工作应重点围绕花岗斑岩脉展开。 相似文献
5.
The Xiaohongshilazi deposit located in central Jilin Province, Northeast China, is a newly discovered and medium‐scale Pb–Zn–(Ag) deposit with ore reserves of 34,968 t Pb, 100,150 t Zn, and 158 t Ag. Two‐stage mineralization has been identified in this deposit. Stratiform volcanic‐associated massive sulfide (VMS) Pb–Zn mineralization interbedding with the marine volcanic rocks of the Late Carboniferous–Early Permian Daheshen Formation was controlled by the premineralization E–W‐trending faults. Vein‐type Pb–Zn–(Ag) mineralization occurs within or parallel to the granodiorite and diorite porphyries controlled by the major‐mineralization N–S‐trending faults that cut the stratiform mineralization and volcanic rocks. To constrain the age of vein‐type Pb–Zn–(Ag) mineralization and determine the relationship between mineralization and magmatism, we conducted LA–ICP–MS U–Pb dating on zircon from the ore‐bearing granodiorite and diorite porphyries and Rb–Sr dating on metal sulfide. Granodiorite and diorite porphyries yield zircon U–Pb weighted‐mean 206Pb/238U ages of 203.6 ± 1.8 Ma (Mean Standard Weighted Deviation [MSWD] = 1.8) and 225.6 ± 5.1 Ma (MSWD = 2.3), respectively. Sulfides from four vein‐type ore samples yield a Rb–Sr isochron age of 195 ± 17 Ma (MSWD = 4.0). These results indicate a temporal relationship between the granodiorite porphyry and vein‐type Pb–Zn–(Ag) mineralization. The granodiorite associated with vein‐type mineralization has high SiO2 (68.99–70.49 wt.%) and Na2O (3.9–4.2 wt.%; Na2O/K2O = 1.07–1.10) concentrations, and A/CNK values of 0.95–1.04; consequently, the intrusion is classified as a high‐K, calc‐alkaline, metaluminous I‐type granite. The granodiorite porphyry is enriched in large‐ion lithophile elements (e.g. Rb, Th, U, and K) and light REE and is depleted in high‐field‐strength elements (e.g. Nb, Ta, P, and Ti) and heavy REE, indicating that it represents a subduction‐related rock that formed at an active continental margin. Furthermore, the granodiorite porphyry has Mg# values of 31–34, indicating a lower crustal source. Based on petrological and geochemical features, we infer that the ore‐bearing granodiorite porphyry was derived from the partial melting of the lower crust. In summary, mineralization characteristics, cross‐cutting relationships, geochronological data, and regional tectonic evolution indicate that the region was the site of VMS Pb–Zn mineralization that produced stratiform orebodies within the Late Carboniferous–Early Permian marine volcanic rocks of the Daheshen Formation, followed by mesothermal magmatic hydrothermal vein‐type Pb–Zn–(Ag) mineralization associated with granodiorite porphyry induced by the initial subduction of the Paleo‐Pacific Plate beneath the Eurasia Plate during the Late Triassic–Early Jurassic. 相似文献
6.
Whole‐rock geochemistry, zircon U–Pb and molybdenite Re–Os geochronology, and Sr–Nd–Hf isotopes analyses were performed on ore‐related dacite porphyry and quartz porphyry at the Yongping Cu–Mo deposit in Southeast China. The geochemical results show that these porphyry stocks have similar REE patterns, and primitive mantle‐normalized spectra show LILE‐enrichment (Ba, Rb, K) and HFSE (Th, Nb, Ta, Ti) depletion. The zircon SHRIMP U–Pb geochronologic results show that the ore‐related porphyries were emplaced at 162–156 Ma. Hydrothermal muscovite of the quartz porphyry yields a plateau age of 162.1 ± 1.4 Ma (2σ). Two hydrothermal biotite samples of the dacite porphyry show plateau ages of 164 ± 1.3 and 163.8 ± 1.3 Ma. Two molybdenite samples from quartz+molybdenite veins contained in the quartz porphyry yield Re–Os ages of 156.7 ± 2.8 Ma and 155.7 ± 3.6 Ma. The ages of molybdenite coeval to zircon and biotite and muscovite ages of the porphyries within the errors suggest that the Mo mineralization was genetically related to the magmatic emplacement. The whole rocks Nd–Sr isotopic data obtained from both the dacite and quartz porphyries suggest partial melting of the Meso‐Proterozoic crust in contribution to the magma process. The zircon Hf isotopic data also indicate the crustal component is the dominated during the magma generation. 相似文献
7.
长江中下游贵池矿集区燕山期岩浆作用及其地质意义:年代学、地球化学及Sr-Nd-Hf同位素证据 总被引：17，自引：10，他引：7
长江中下游贵池地区燕山期侵入岩发育,与成矿关系密切.本文对该区侵入岩开展了详细的锆石U-Pb年代学、地球化学及Sr-Nd-Hf同位素研究.结果表明,马头花岗闪长斑岩形成于147±2Ma,而花园巩石英二长岩形成于127±1Ma,比花岗闪长斑岩晚约20Ma.早期的花岗闪长斑岩(147 ～ 145Ma)为高钾钙碱性系列,具有高Al2O3、Sr含量和Sr/Y、La/Yb比值,以及低的Y、Yb含量,与埃达克质岩的地球化学特征一致;而晚期石英二长岩(127Ma)和石英正长岩为钾玄岩系列,具有高的(Na2O+ K2O)、Zr、Nb、Y含量和Y/Nb、Yb/Ta比值,与造山带A2型花岗岩地球化学特征相似;碱长花岗岩(125～124Ma)同样具有A型花岗岩的地球化学特征,但与石英二长岩、石英正长岩相比,碱长花岗岩的Y/Nb、Yb/Ta比值相对较低,具板内环境A1型花岗岩的地球化学特征.因此,贵池地区岩浆岩从早期的埃达克质岩变为晚期的A型花岗岩,反应了晚中生代时期长江中下游地区的构造环境由大陆边缘环境向伸展环境的转变. 相似文献
8.
LA-ICP-MS Zircon U-Pb Geochronology of Quartz Porphyry from the Niutougou Gold Deposit in Songxian County,Henan Province 总被引：4，自引：0，他引：4
The Niutougou gold deposit,located in the center of the Xiong’ershan gold district,western Henan Province,is a large gold deposit with many quartz porphyries found in the area.Based on the field geological investigation of quartz porphyry of Niutougou gold deposit and by using the cathodoluminescence(CL) images analysis and in situ LA-ICP-MS U-Pb isotope dating method of zircons,the inner structure,trace element compositions and U-Pb age of the zircons separated from quartz porphyry were analyzed and determined.Cathodoluminescence(CL) images of zircons show clear magmatic zonations.Trace element analyses of zircons reveal that all zircons show high concentrations of Th,U,and HREE,and the REE patterns of depletion in LREE,with a positive Ce anomaly.Zircon LA-ICP-MS U-Pb dating results show that the quartz porphyry in the Niutougou gold deposit was formed at 159.71±0.99 Ma(about 160 Ma),belonging to the product of magmatic activity in late Middle Jurassic.Combined with the geological characteristics of the Niutougou gold deposit,the formation age of the quartz porphyry and the analysis of the formation age of the granite body exposed in the Niutougou gold deposit,the study suggests that the metallogenic epoch of the Niutougou gold deposit may be Yanshanian in age. 相似文献
9.
对出露于滇西龙陵的二长花岗岩进行了系统的地球化学研究,重点讨论了奥陶纪二长花岗岩的岩石成因、成岩物质来源及其构造环境。二长花岗岩SiO2和Al2O3的含量均很高,SiO2含量变化为72.17%~76.45%,A/CNK为0.86~1.45（平均1.12）,为Si和Al过饱和类型,属典型的过铝质花岗岩。稀土元素总量（∑REE）为（138.17~383.68）×10-6,稀土元素配分曲线呈右倾型,Eu为负异常。具有富集K、Sr、Rb、Ba等大离子亲石元素,亏损Zr、Ta、Nb、Th等高场强元素的特点。岩石可能是以砂岩成分为主的沉积岩部分熔融形成的花岗质岩浆上升侵位形成的,是一种典型的壳源成因类型。LA-ICP-MS锆石U-Pb定年表明,勐冒花岗岩形成于中奥陶世（454.7Ma±1.5Ma）。奥陶纪二长花岗岩具有后碰撞岩浆活动的特征,代表冈瓦纳大陆造山运动后期岩浆活动的产物,形成于同碰撞（挤压环境）向碰撞后（伸展环境）转化阶段,为后碰撞花岗岩类,对揭示滇西地区怒江断裂带的构造属性有重要意义。 相似文献
10.
Junxing ZHAO Kezhang QIN Guangming LI Jinxiang LI Bo XIAO Lei CHEN 《Resource Geology》2012,62(1):84-98
The Sharang porphyry Mo deposit is the first discovered Mo porphyry‐type deposit in the Gangdese Metallogenic Belt. The orebody is hosted by the Eocene multi‐stage composite intrusive complex which is emplaced in the Upper Permian Mengla Formation and cut by the Miocene dykes. Granite porphyry is recognized as the ore‐bearing porphyry in the complex, which consists of quartz diorite, quartz monzonite, granite, prophyritic granite and post‐mineral lamprophyre. Granodiorite porphyry and dacite porphyry intrude the granite porphyry. Geochemical data indicate that Sharang complex has a High‐K calc‐alkalinc to shoshonitic, metaluminous to slightly peraluminous composition. The Sharang complex rocks are enriched in large ion lithophile elements, depleted in high‐field strength elements, Nb, Sr, P and Ti. REE patterns show slight enrichments in light REE relative to heavy REE and weak negative Eu anomalies. All rocks in this complex have a wide range of initial 87Sr/86Sr ratios (0.705605～0.712496) and lower εNd(t) values (?0.61～?7.80). The geochemical data suggest highly oxidized‐evolved magma and old continental materials may have been the magma source for the Sharang intrusive complex that host porphyry Mo mineralization. Eocene pre‐ore and ore‐forming rocks at Sharang may have formed by partial melting of mantle wedge and by mixing with old continental crust at the lower crust level. In contrast the post‐ore rocks may have formed by partial melting of enriched lithospheric mantle. 相似文献
11.
当家寺花岗岩体是青海南山印支期花岗岩带中东部较大的一个岩体,形成于早三叠世(243.5±2.9 Ma、247.2±1.7 Ma)—中三叠世(240.1±2.1 Ma、241.0±2.6 Ma)。岩体内发育有众多的中-酸性脉岩,岩石类型主要为闪长玢岩、石英闪长玢岩、花岗斑岩等,本研究获得闪长玢岩脉LA-MC-ICP-MS锆石U-Pb年龄为(235.6±2.4 Ma),表明其形成于晚三叠世早期,稍晚于当家寺岩体侵位时限。脉岩作为一种浅成侵入体,其与当家寺花岗岩体分布的构造位置相似,矿物组成及地球化学特征具有近似的特点,说明二者岩石成因及构造背景类似,可能为同一源区壳-幔岩浆混合作用的产物。岩石地球化学分析表明中性脉岩SiO2含量低(54.68%~64.75%),酸性脉岩SiO2含量高(66.00%~77.13%),二者都具高铝(Al2O3=12.24%~17.11%)、高钾钙碱性准铝质-弱铝质的特点(A/CNK=0.85~1.04),具有典型的岛弧花岗岩和碰撞花岗岩的特征。脉岩富集LREE、Rb、Th、K,亏损HREE、Nb、Ta、P、Ti、Ba,(La/Yb)N=5.05~17.61,表现出中等强度Eu的负异常。综合分析认为,脉岩形成于晚三叠世共和裂谷闭合碰撞造山后构造环境由挤压向板内稳定-伸展的变迁阶段,指示晚三叠世早期共和盆地周缘已进入后碰撞的陆内环境。 相似文献
12.
The Yanhu granitoids are located in the west segment of the Bangongco-Nujiang suture in the western Tibetan Plateau. The main rock types of the granitoids are diorite porphyry, quartz diorite, granodiorite, granite and granite porphyry. Here, their zircon LA-ICP-MS U-Pb ages and petrogeochemical data are reported. Three groups of magmatic events can be distinguished from the Yanhu area: group 1 includes samples AK01 and ZK01 of diorite porphyry, and sample D3658 of quartz diorite that yield mean zircon U-Pb ages of 121.0 ± 2.7 Ma, 116.6 ± 2.0 Ma and 116.0 ± 3.9 Ma, respectively; group 2 includes sample D0050 of diorite porphyry, samples D1393 and D3660 of granodiorite and sample D3065 of granite porphyry that yield mean zircon U-Pb ages of 104.9 ± 2.0 Ma, 105.4 ± 3.8 Ma, 104.2 ± 1.9 Ma and 104.2 ± 1.9 Ma, respectively; group 3 includes sample D3093 of granite that yields mean zircon U-Pb ages of 93.6 ± 1.5 Ma. The zircon LA-ICP-MS U-Pb ages suggest that the Yanhu granitoids were emplaced at 121.0–93.6 Ma, representing Cretaceous magmatism in the west segment of the Bangongco-Nujiang suture. The granitoids are composed of SiO2 (56.57 to 76.98 wt.%), Al2O3 (12.20 to 17.90 wt.%), Na2O (3.61 to 4.98 wt.%), K2O (2.06 to 4.71 wt.%) and CaO (0.27 to 5.74 wt.%). The Yanhu granitoids exhibit enrichment in LREE (light REE) and LILE (large ion lithophile elements) such as Rb, Th, U, Pb and K and depletion of HREE (heavy REE), P, Ti, Nb, Ta and Zr. Their A/CNK ratios of 0.85-1.06 are <1.1, implying that they are high-K, metaluminous-weakly peraluminous I-type granites. TheYanhu granitoids were generated mainly by partial melts of the meta-igneous lower crust and some arc-related materials. The Yanhu granitoids probably formed in VAG and syn-COLG tectonic settings related to the southward subduction of the Tethyan Ocean. Diorite porphyry and quartz diorite magmatism from 121.0 Ma to 116.0 Ma may be associated with the southward Bangongco–Nujiang Tethys oceanic crust subduction. Diorite porphyry, granodiorite, and granite porphyry magmatism from 105.4 Ma to 104.2 Ma may be associated with the rising asthenosphere induced by the slab breakoff. Granite magmatism from 93.6 Ma may be related to the crustal thickening induced by the final amalgamation of the Lhasa Terrane and the Qiangtang Terrane. 相似文献
13.
《Resource Geology》2018,68(4):337-351
The Bayinsukhtu tungsten deposit is a newly discovered quartz‐vein tungsten deposit in the Xing'an–Mongolia Orogenic Belt (XMOB) in southern Mongolia, hosted by the Bayinsukhtu granite porphyry. The granite porphyry is located mainly south of the study area, over 3 km2. The rock consists of quartz and feldspar phenocrysts in a fine‐grained matrix, also mainly composed of feldspar and quartz. The granite porphyry samples demonstrate high SiO2 and high alkalinity. All samples also straddle the high‐potassium calc‐alkaline series. In a plot of the molar ratios of A/NK versus A/CNK, the granites are metaluminous. The chondrite‐normalized REE patterns are characterized by large negative Eu anomalies and fractionated LREEs. The U–Pb age of zircons from the granite porphyry is 298.8 ± 1.8 Ma, and the Sm–Nd age of the five wolframite samples from the tungsten deposit is 303 ± 19 Ma. The cooling age of the granite porphyry and tungsten mineralization is within the error of measurement and is of the Late Carboniferous age. Geological and geochronological evidence shows that the tungsten mineralization and the granite porphyry at Bayinsukhtu are genetically closely related and that they are results of Carboniferous magmatism. Their tectonic setting is related to the accretion of the Central Asian Orogenic Belt during the late Paleozoic era. 相似文献
14.
Shunso Ishihara 《Resource Geology》2008,58(4):423-427
The chemical composition of zircons from S‐ and I‐type ilmenite‐series granitic rocks in the Chubu district is summarized based upon recent electron probe microanalysis. Zircons in S‐type Busetsu granite of the Ryoke Metamorphic Belt have a homogeneous composition with minimum impurities, whereas those of I‐type Naegi granite in the non‐metamorphic Sanyo Belt are enriched in Hf, Y, REE, Th and U along the crystal rims. Similar enrichment has been observed in a variety of zircon called Naegite. These minor components are concentrated in the F‐rich fluid phase of residual melts of the Naegi granite magma, and are crystallized in pegmatites during the latest magmatic stage. High values of Nb and Ta in some Naegite reported previously are attributed to micro‐inclusion of fergusonite. 相似文献
15.
哈西亚图铁多金属矿位于东昆仑构造带,是区域较为典型的一处矽卡岩型矿床.文章对矿区花岗闪长岩开展了LA-ICP-MS锆石U-Pb同位素测定与岩石地球化学研究,结果表明花岗闪长岩中锆石的年龄为(240.1±0.8)Ma(MSWD=0.62),形成于中三叠世,岩石为准铝高钾钙碱性系列,轻稀土富集,轻重稀土分馏明显,具弱的负铕异常,富集大离子亲石元素(Rb、K等),同时表现出“TNT”(Ta、Nb、Ti)负异常等俯冲带幔源岩石的成分特点.依据岩石学、地球化学特征并结合同时期大地构造背景认为:花岗闪长岩产于中生代岩浆弧环境,区域同时期花岗闪长岩与石英闪长岩有着相同的物质来源与产出背景.在其他具有矽卡岩型矿化潜力的区域,今后找矿工作中应注重花岗闪长岩的成矿作用. 相似文献
16.
帕米尔东缘杜格里富碱斑岩锆石U-Pb定年、地球化学特征及构造意义 总被引：1，自引：0，他引：1
帕米尔构造结是陆陆碰撞造山的典型地区之一,位于帕米尔东缘的杜格里富碱斑岩是揭示帕米尔新生代构造演化的重要对象。岩体侵位于下二叠统粉砂质板岩中,主要由正长斑岩和石英正长斑岩组成。通过锆石LA-ICP-MS U-Pb定年获得岩体的成岩年龄为10.76±0.09 Ma,表明杜格里富碱斑岩形成于中新世中期。地球化学分析结果显示,杜格里岩体具富碱、高钾、准铝质—弱过铝质的特征,微量元素高度富集Rb、Sr、Ba等大离子亲石元素(LILE),而亏损Nb、Ta、Ti等高场强元素(HFSE),稀土元素总量较高,球粒陨石标准化配分型式呈右陡倾的LREE富集型,且无明显负Eu异常,反应源区为加厚镁铁质下地壳,并经历过古俯冲洋壳板片流体的交代作用和富集地幔物质的加入。综合分析认为,杜格里富碱斑岩形成于后碰撞阶段伸展构造体制下,是青藏高原西北缘构造转换带对印度-欧亚大陆碰撞造山过程响应的记录。 相似文献
17.
The Tibetan Plateau is one of the most significant Cu poly-metallic mineralization regions in the world and preserves important information related to subductional and collisional porphyry Cu mineralization. This study investigates a new occurrence of Cu mineralization-related andesitic porphyries in the western domain of the Gangdese magmatic belt and assesses its petrologic, zircon U-Pb geochronology, whole-rock chemistry, and Sr-Nd-Hf-Pb isotope data. Zircon U-Pb dating of three ore-related porphyries yields crystallization ages of 212–211 Ma. These ages are consistent with previous molybdenite Re-Os dating, indicating a late Triassic magmatic and Cu mineralization event in the western Gangdese magmatic belt. Nb, Ta, and Ti depletion, Th and LREE enrichment, and high La/Yb and Th/Yb ratios in addition to high U/Yb ratios from zircons suggest that the magma was generated in an active continental arc setting. The porphyries have radiogenic isotopic compositions with (87Sr/86Sr)i 0.70431–0.70473, εNd(t) +1.1 to +3.8, (207Pb/204Pb)i 15.601–15.622, and (208Pb/204Pb)i 38.450–38.693, as well as high positive zircon εHf(t) values from +6.2 to +10.6 (mean value 8.3), corresponding to model ages (TDM) ranging from 509 Ma to 819 Ma (mean 646 Ma). This suggests that the andesitic magmatism was dominantly sourced from depleted mantle materials that were modified by subducted oceanic sediment-derived melts during the subduction of the Neo-Tethys Ocean. The mineralization-related porphyries contain amphibole and epidote, as well as high whole-rock Fe2O3/FeO and zircon Ce4+/Ce3+ ratios, suggesting hydrous and highly oxidized parent magmas. Considering the existing Cu mineralization and highly oxidized magma of the well-preserved Triassic andesitic igneous rocks in the western Gangdese belt, the subduction-related continental arc magma system is favorable for subduction-related porphyry Cu deposits. The existence of Luerma porphyry mineralization demonstrates that there are at least five generations of porphyry Cu-(Mo-Au) mineralization in the Gangdese magmatic belt, which advances the timeframe of porphyry mineralization to the late Triassic. 相似文献
18.
GAO Yongfeng HOU Zengqian WEI Ruihua ZHAO RongshengShijiazhuang College of Economy Huainan Ro Shijiazhuang Hebei E-mail: gao@sina.comInstitute of Mineral Resources Chinese Academy of Geological Sciences Beijing Hebei Bureau of Land Resources Shijiazhuang Hebei 《《地质学报》英文版》2003,77(2):194-203
The distribution of Neogene felsic porphyries intruding in earlier granitic batholiths was mainly controlled by north-south-tending rifting zones and normal faults. The main rock types of the felsic porphyries include granodiorite-porphyry, monzonitic granite-porphyry and quartz monzonitic porphyry. The porphyries are characterized by high SiO2 ((?)64.26%) and Al2O3 (>15% at 70% SiO2), low Y and HREE (Yb) contents, strong enrichment of LILE and LERR, especially K and ST. Geochemical features of the porphyries show distinct adakitic magma affinity. Nd, Sr and Pb isotopic compositions of the porphyries form a linear alignment from MORB to EM2, suggesting a mixing of the MORB reservoir with the metasomatized mantle reservoir. Considering also the geochemical characteristics of the porphyries and the sequence of observable structural-thermal-magmatic events at Gangdise, it is thought that the Neogene porphyries were formed by partial melting of dead subducted oceanic crust in a post-collision setting. K-enr 相似文献
19.
新疆富蕴地区希勒库都克铜钼矿床含矿斑岩的年代学与地球化学特征 总被引：14，自引：0，他引：14
位于新疆富蕴县境内的希勒库都克铜钼矿属于斑岩型矿床。含矿花岗斑岩和石英闪长岩为弱过铝质高钾钙碱性岩石,具有相对富集大离子亲石元素、亏损Nb、Ta、Ti元素的地球化学特征。获得含矿花岗斑岩SIMS锆石Ｕ-Pb年龄（329.6±4.1）Ma。综合分析,花岗斑岩和石英闪长岩可能为同一岩浆不同演化阶段的产物。据含矿岩石高的正εNd（t）值、低的87Sr/86Sr初始值推测,其原始岩浆起源于亏损地幔源区。 相似文献
20.
蒙古-鄂霍茨克洋俯冲的记录：额尔古纳地区八大关变质杂岩的证据 总被引：4，自引：1，他引：3
本文对额尔古纳地块西缘八大关杂岩进行了锆石LA-ICP-MS U-Pb定年和岩石地球化学分析,以确定该套杂岩的形成时代及其构造属性。原定义为"佳疙瘩组"的八大关杂岩主要由黑云角闪斜长片麻岩和花岗质糜棱岩组成。LA-ICP MS锆石U-Pb研究表明,3个样品的锆石发育典型的岩浆振荡环带,高Th/U(0.13~1.42),轻稀土元素亏损,重稀土元素富集,具有强烈的正Ce异常和强烈的负Eu异常等特征,表明锆石均属于岩浆成因。测年结果表明2个黑云角闪斜长片麻岩形成时代分别为210±2Ma、214±2Ma,花岗质糜棱岩的原岩年龄为203±3Ma;样品中同时存在~501Ma和~795Ma的捕获/继承锆石。上述结果显示八大关杂岩的形成时代应为晚三叠世而不是前人认为的新元古代,而捕获锆石则显示与东北其它地块具有相同的构造演化历史。地球化学研究显示,八大关杂岩具有高钠、铝等特点,A/CNK=0.86~1.05,A/NK=1.53~1.97,为准铝质到弱过铝质钙碱性系列;轻稀土元素富集、重稀土元素亏损(La/Yb)N=6~31,Eu弱亏损(Eu/Eu*=0.50~1.01),具有较高的Sr含量(在378×10-6~598×10-6之间)及低的Yb含量(在0.71×10-6~3.50×10-6之间);微量元素原始地幔标准化蛛网模式图显示,富集Rb、Ba、K及Sr等大离子亲石元素、强烈亏损Nb、Ta、P、Ce及Ti等高场强元素。这些地球化学特征表明八大关杂岩形成于活动大陆边缘的岛弧环境。因此,八大关杂岩应形成于蒙古-鄂霍茨克洋向额尔古纳地块俯冲的大地构造背景,为蒙古-鄂霍茨克洋在三叠纪晚期南向俯冲提供了关键证据。 相似文献