陕西华县八里坡钼矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

八里坡钼矿是在金堆城钼矿床外围找矿中新发现的斑岩型钼矿床,对其含矿斑岩和矿石进行了成岩成矿年龄精测。采用LA-ICP-MS方法对八里坡斑岩体进行单颗粒锆石U-Pb测年,获得成岩年为155.9±2.3 Ma;采用ICP-MS法测定八里坡钼矿中辉钼矿Re-Os同位素年龄,获得模式年龄为156.3±2.2 Ma;两种方法获得的年龄一致,表明成岩与成矿同时形成。八里坡斑岩体与东秦岭南泥湖、上房沟等斑岩体成岩年龄一致,早于金堆城钼矿床成矿年龄,表明八里坡斑岩体可能是新一期成岩成矿作用,形成于燕山运动的A幕,产出于东亚构造体制转变初期的地球动力学背景,具有重要成岩成矿意义。     

SHRIMP Zircon U-Pb and Molybdenite Re-Os Datings of the Superlarge Donggou Porphyry Molybdenum Deposit in the East Qinling, China,and Its Geological Implications

Located in the eastern part of the East Qinling molybdenum belt, the Donggou deposit is a superlarge porphyry molybdenum deposit discovered in recent years. The authors performed highly precise dating of the mineralized porphyry and ores in the Donggou molybdenum deposit. A SHRIMP U-Pb zircon dating of the Donggou aluminous A-type granite-porphyry gave a rock-forming age of 112±1 Ma, and the ICP-MS Re-Os analyses of molybdenite from the molybdenum deposit yielded ReOs model ages ranging from 116.5±1.7 to 115.5±1.7 Ma for the deposit. The ages obtained by the two methods are quite close, suggesting that the rocks and ores formed approximately at the same time. The Donggou molybdenum deposit formed at least 20 Ma later than the Jinduicheng, Nannihu, Shangfanggou and Leimengou porphyry molybdenum deposits in the same molybdenum belt, implying that these deposits were formed in different tectonic settings.     

Late Jurassic Cu-Mo Mineralization at the Zhashui-Shanyang District, South Qinling, China: Constraints from Re-Os Molybdenite and Laser Ablation-Inductively Coupled Plasma Mass Spectrometry U-Pb Zircon Dating

The Zhashui-Shanyang district is one of the most important sulfide deposits in the Qinling Orogen where the formation of porphyry-skarn Cu-Mo deposits has a close genetic link with the Yanshannian magmatism. Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb zircon dating of two granodiorite intrusions (Xiaohekou and Lengshuigou deposits) was investigated in the Zhashui-Shanyang district and the rock-forming ages obtained from 148.3±2.8?to 152.6±1.2?Ma, averaging 150.5 Ma, accompanied by a younger disturbance age of 144.3±1.7?Ma in the Lengshuigou intrusion, which is in excellent agreement with published sensitive high resolution ion micro-probe (SHRIMP) zircon date on the later monzodiorite porphyry phase in the Lenshuigou deposit. Two samples were selected for molybdenite ICP-MS Re-Os isotopic analyses from the Lengshuigou granodiorite porphyry, yielding Re-Os model ages from 149.2±2.7 Ma to 150.6±3.4 Ma, with a weighted mean age of 149.7±2.1 Ma. These mineralization ages overlap rock-forming ages of the host intrusions within the error range. This implies that the mineralization occurred in the Late Jurassic, which belongs to the tectonic phase B event of the Yanshan Movement, not Cretaceous as previously thought. Therefore, the Late Jurassic mineralization of the Zhashui-Shanyang district could be connected to the large-scale Yanshan molybdenum metallogenic period, the geodynamic regime of which is attributable to the far field response of convergence of surrounding plates, perhaps the approximately westward subduction of the Izanagi plate beneath the Eurasian continent.     

Re-Os Geochronology of Molybdenite from Yuanzhuding Porphyry Cu-Mo Deposit in South China

The Yuanzhuding porphyry Cu-Mo deposit, discovered in 2008, is located within the southern segment of the Chenzhou-Huaiji fault belt, South China. The deposit is hosted within the Upper Cambrian neritic facies sandstone and shale formation that is the strata of the axis and wings of within the Yuanzhuding anticline. Both of the porphyry and exo-contact zone contain Cu-Mo mineralization. Economic orebodies occur mainly in the exo-contact zone around the porphyry. We dated 11 molybdenite samples obtained from two borehole cores of the deposit, using the Re-Os method. Analyses of eight molybdenite samples from borehole ZK12-112 yield a Re-Os isochron age of 157.3 ± 4.3 Ma (2σ), and analyses of 11 samples from boreholes ZK12-112 and ZK16-104 yield a Re-Os isochron age of 155.6 ± 3.4 Ma (2σ). These isochron ages are within the error of the Re-Os model ages, demonstrating that the age results are reliable and that the Yuanzhuding porphyry Cu-Mo deposit formed during the late Middle Jurassic. The formation age of the Yuanzhuding Cu-Mo deposit is similar to the age of intermediate-acid rocks and W-Sn polymetallic deposits along the Chenzhou-Huaiji fault belt. This concordance suggests the same geodynamic process to the igneous activity and related mineralization, raising the potentiality of the porphyry Cu-Mo mineralization in the belt.     

赣南盘古山钨矿床锆石U-Pb和辉钼矿Re-Os年龄及其意义

盘古山钨矿是一个历史悠久、闻名国内外的大型矿床,为了厘定其岩浆活动及成矿作用时代,进而认识成岩与成矿关系、岩体内带与外带矿化关系及成岩成矿动力学背景,本研究采用LA-ICP-MS锆石U-Pb和ICP-MS辉钼矿Re-Os分析法分别对南岭2000 m科学钻探(SP-NLSD-2)所揭露的隐伏花岗岩体及其内带矿化石英脉进行了年龄测定。结果表明,隐伏花岗岩体形成于(161.7±1.6)Ma,内带矿化石英脉年龄为(155.3±2.8)Ma,均形成于中—晚侏罗世。盘古山钨矿床花岗岩浆活动与成矿作用的时代在误差范围内基本一致,矿化发育于岩体内外接触带,在空间上关系密切,并表现出花岗岩体→长石石英脉→石英脉的渐变演化关系,结合前人研究成果表明,矿化石英脉是花岗岩浆分异演化晚期的产物。岩体内带石英脉与外带石英脉的形成年龄吻合较好,形成于同一成矿作用。盘古山钨矿床及其隐伏花岗岩体均形成于165~150 Ma华南岩石圈伸展-岩体侵位-大规模成矿的动力学环境。     

东秦岭东沟超大型斑岩钼矿SHRIMP锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

东沟钼矿是在东秦岭钼矿带中于近年新发现的超大型斑岩钼矿床。对其含矿斑岩和矿石进行了成岩成矿年龄精测。采用SHRIMP锆石U-Pb测年技术,对东沟含矿铝质A型花岗斑岩体进行了年代学研究,获得成岩年龄为112±1Ma;采用ICP-MS法测定东沟钼矿中辉钼矿Re-Os同位素年龄,获得模式年龄为116.5±1.7~115.5±1.7Ma;两种方法获得的年龄相近,表明成岩与成矿大致同时形成。东沟斑岩钼矿与东秦岭金堆城、南泥湖、上房沟、雷门沟等斑岩钼矿具有20Ma以上的时差,反映它们形成于不同的地球动力学背景。     

湘东宏夏桥和板杉铺岩体LA-MC-ICPMS锆石U-Pb年龄及地质意义

运用阴极发光技术,对湖南东部宏夏桥和板杉铺岩体的锆石进行了内部结构分析,在此基础上利用LA-MC-ICPMS锆石U-Pb定年方法进行了同位素年代学测定。结果显示,宏夏桥2个黑云母花岗闪长岩样品分别给出了(421±2)Ma和(423±2)Ma的主体谐和年龄;板杉铺2个黑云母二长花岗岩样品给出了(422±2)Ma和(421±2)Ma的谐和年龄。这两岩体均为准铝质-过铝质花岗岩,具明显高Sr/Y和La/Yb比值和负εNd(t)值,与埃达克岩类似,推测它们为早古生代华南地壳缩短加厚和部分熔融作用的产物。综合区域岩浆和变形变质年龄,本文认为,华南早古生代陆内挤压造山作用发生于~460~420 Ma,以前泥盆纪地层广泛褶皱和大规模地壳重熔型岩浆活动、混合岩化作用、基底韧性剪切及高级变质作用为主;陆内造山后期的伸展松弛作用发生于~420~385 Ma,主要表现为后造山花岗岩形成、张扭性韧性剪切和退变质作用。     

安徽沙坪沟斑岩钼矿锆石U-Pb和辉钼矿Re-Os年龄

沙坪沟斑岩钼矿是大别成矿带近年发现的超大型矿床。在对矿化特征分析的基础上,对其进行了成岩成矿年代学研究。采用LA-ICP-MS锆石U-Pb测年技术,得到含矿岩体的成岩年龄。细粒石英正长岩与中粒石英正长岩分别形成于122.51±0.81Ma和121.5±1.3Ma,正长斑岩形成于120.7±1.1Ma。通过矿床辉钼矿Re-Os同位素分析,获得其模式年龄为100±1.8～113.6±1.7Ma。成岩与成矿时差约7Ma,指示含矿热液活动时限较长。长时间的热液活动可能是形成沙坪沟超大型斑岩钼矿床的重要因素。沙坪沟钼成矿时间与大别带钼矿化时间(133～110Ma)高度一致,与东秦岭晚期钼矿化时间相同。大别带钼矿是秦岭-大别成矿带的组成部分,形成于相同构造背景下,是区域构造岩浆作用的产物。     

南秦岭花岗岩锆石U-Pb定年及其地质意义

锆石Ｕ－Ｐｂ定年结果表明,南秦岭勉、略构造带以北迷坝、光头山和东江口等花岗岩体形成于三叠纪（２０６￣２２０Ｍａ）,与南秦岭勉－略构造带洋盆的闭合时代及大别山超高压变质时代基本一致显示了它们的形成与勉－略古生代洋盆闭合后及华南陆块与华北陆块碰撞之间的内在联系。它支持华南和华北两大陆块最终在印支期碰撞的观点。     

大别山北缘千鹅冲斑岩型钼矿床锆石U-Pb和辉钼矿Re-Os年代学及其地质意义

河南省光山县千鹅冲钼矿床是大别山地区近年最新发现的大型斑岩型钼矿床。采用LA-ICP-MS锆石U-Pb和ICP-MS辉钼矿Re-Os同位素精细测年技术,对与成矿相关的宝安寨钾长花岗岩、千鹅冲花岗斑岩2个锆石样品和4个细网脉型钼矿石中的辉钼矿样品进行了同位素年代学测定,分别获得(135.3±1.9),(128.8±2.6),(127.82±0.87)Ma的同位素年龄。结果表明,千鹅冲钼矿床成矿作用时间与千鹅冲花岗斑岩成岩作用时间一致,晚于大别山巨量花岗质岩浆活动近7Ma,它们为统一构造背景同期不同次岩浆作用的产物。与成矿相关岩体的地球化学研究结果显示,岩体具有低Sr(wB400×10-6)、低Yb(wB1.8×10-6)、中等程度Eu负异常[δ(Eu)0.5]、轻重REE强烈分异{[w(La)/w(Yb)]N24}等特征,其Sr-Nd同位素显示较高的[N(87Sr)/N(86Sr)]i(0.70669～0.72422,变化较大)和极低的ε(Nd)(t)(-18.01～-21.37)。综合分析表明成岩成矿作用发生在大别造山带碰撞造山后构造体制由挤压收缩向伸展的转折时期,与成矿有关的酸性侵入岩是加厚陆壳部分熔融作用的产物。千鹅冲斑岩型钼矿床与成矿带内汤家坪、大银尖、天目山、银山、东沟钼矿床在成矿时间及成矿岩体地球化学特征的显著差异,反映它们形成于造山带演化的不同历史时期和不同的构造动力学背景。     

华南新元古代花岗岩的锆石U-Pb年龄及其构造意义

SHRIMP锆石U Pb年龄测定结果表明 ,云南峨山、江西九岭和安徽许村等 3个岩体的形成年龄分别为818± 10Ma、818± 10Ma和 82 9± 11Ma ,与广西北部的本洞、三防、元宝山、湖北的黄陵岩体以及的广西北部的基性岩墙的年龄完全一致 ,表明在 82 0～ 830Ma期间 ,扬子克拉通在广大区域内几乎同时发生了广泛的地壳重熔和幔源基性岩浆活动。虽然这些花岗岩的类型不同 ,但它们的形成时代相当一致 ,表明这些不同类型的花岗岩应形成于相同或相关的构造环境 ,很可能是地幔柱活动导致下地壳重熔的产物。     

赣南矽卡岩型钨矿成岩成矿年代学及地质意义——以焦里和宝山矿床为例

矽卡岩型钨矿是赣南地区的一种重要钨矿床类型。本文以焦里和宝山两个典型的矽卡岩型钨多金属矿床为例,开展了系统的成岩成矿年代学和岩石地球化学研究,结合区域钨锡矿床最新年代学研究成果,探讨了赣南地区钨矿的成岩成矿时代及形成构造环境。结果表明,焦里矽卡岩型钨多金属矿区斑状花岗闪长岩SHRIMP锆石U-Pb年龄为164.4±1.1Ma,辉钼矿Re-Os等时线年龄为170.6±4.6Ma;宝山矽卡岩型钨矿区花岗岩SHRIMP锆石U-Pb年龄为156.6±3.9Ma,辉钼矿Re-Os模式年龄加权平均值为161.0±1.9Ma,厘定了它们的成岩成矿年龄为中-晚侏罗世,同一矿区的成岩和成矿年龄在误差范围内基本一致。结合赣南崇(义)-(大)余-(上)犹钨锡矿集区已有的年代学资料,指出本区的成岩成矿年龄介于170～150Ma,集中在160～150Ma,认为赣南钨矿形成于华南中生代岩石圈伸展-减薄时期的侏罗纪板内拉张的地球动力学背景,系同一成岩成矿系统的产物。     

Re-Os Dating of Molybdenite from the Yaogangxian Tungsten Deposit, South China, and Its Geological Significance

The Yaogangxian tungsten deposit is located in the central part of the Nanling polymetailic metallogenic province. The orebodies occur as veins. Wolframite and molybdenite are the dominant ore minerals. Two samples were selected for molybdenite Re-Os dating in order to elucidate the timing of mineralization. Re-Os datings of molybdenite from quartz-woiframite veins and disseminated in granite yield ages of 153±7 Ma and 163.2±4.2 Ma respectively. The results indicate that the Yaogangxian tungsten deposit is the product of large-scale metallogenesis in the middle Yanshanian period in South China, and that the evolution from late magmatic to postmagmatic hypothermal mineralization occurred at about 10 Ma. The rhenium content of molybdenite in the Yaogangxian tungsten deposit suggests that the ore materials originated from the crust.     

江西九瑞地区东雷湾矽卡岩型铜多金属矿床锆石U-Pb和辉钼矿Re-Os年龄及其地质意义

东雷湾矽卡岩型铜钼金多金属矿床位于九瑞矿集区西北部。本文利用锆石 LA-MC-ICP MS U-Pb同位素定年方法,对东雷湾的主要岩体花岗闪长斑岩成岩时代进行研究,获得花岗闪长斑岩的锆石U-Pb年龄为(142.24±0.52) Ma;同时采用辉钼矿Re-Os同位素定年方法对矿床石英硫化物中的辉钼矿进行定年,首次获得东雷湾矿床的成矿年龄:6件辉钼矿的Re-Os同位素模式年龄范围为(144.8±3.1)~(147.1±2.4) Ma,加权平均年龄为(146.12±0.97) Ma,等时线年龄为(143.3±5.2) Ma。成岩年龄与成矿年龄在误差范围内一致,存在较短的成岩成矿时差,表明成岩成矿过程连续。辉钼矿的Re含量指示东雷湾矿床的成矿作用与岩浆壳幔混合作用有关。东雷湾矿区的成岩成矿时代与九瑞矿集区典型岩体和矿床的成岩成矿时代相似,同时也与长江中下游地区铜陵、安庆和鄂东南(部分地区)的典型铜多金属矿床的成岩成矿时代基本一致。结合区域地质资料,本文认为东雷湾矿床是中国东部东西向印支期构造域向北东向古太平洋构造域构造体制大转折晚期成矿作用的产物。     

江西省都昌县阳储岭钨钼矿年代学研究

江西省都昌县阳储岭钨钼矿床位于江南造山带东段,为准确厘定阳储岭钨钼矿床的成岩成矿时代,本次在详实的野外地质调查基础上,对阳储岭成矿花岗闪长斑进行锆石U-Pb定年工作,同时开展辉钼矿Re-Os同位素定年研究。LA-ICP-MS锆石U-Pb年龄为（145.08±0.35）Ma（MSWD=0.51,n=7）;辉钼矿Re-Os模式年龄为（143.3±2.0）Ma~（145.5±2.2）Ma,等时线年龄为（145.4±1.0）Ma。阳储岭成矿花岗闪长斑岩锆石U-Pb年龄与辉钼矿Re-Os等时线年龄基本一致,表明阳储岭钨钼矿床成岩成矿时代约为145 Ma。辉钼矿中Re含量为16.62×10^-6~87.76×10^-6,平均值为44.68×10^-6,与壳幔混源岩浆热液矿床中Re的含量相似,指示阳储岭钨钼矿床成矿物质来源于壳幔混源。     

西藏许如错地区古近纪盆地碎屑锆石U-Pb年代学充填记录分析

西藏许如错地区在国内鲜有学者研究,仅在少有的区域地质报告中出现。研究区内发育一套古近系碎屑岩沉积——日贡拉组,该地层在研究区局部具有一套火山岩夹层。文章通过对许如错地区古近系日贡拉组碎屑锆石的LA-ICP-MS U-Pb测年分析,结合周边盆地年龄结构及研究区沉积现象,进而追寻盆地沉积物物源和盆地充填记录。研究表明,日贡拉组为一套由粗变细最终又变粗的碎屑岩沉积夹少量火山岩,根据沉积原生构造和宏观剖面判断其主要是扇三角洲-浅湖相-扇三角洲的沉积环境;岩浆成因的碎屑锆石年龄峰值集中在127～134 Ma年龄段内,结合周缘年龄推断日贡拉组物源来自北—北西中部拉萨地块的早白垩世花岗岩。通过对研究区日贡拉组岩石组合、岩石地层序列、物源分析、沉积演化过程以及年代证据等方面的研究,发现日贡拉组的发育处于青藏高原俯冲碰撞隆升阶段和汇聚挤压隆升阶段。     

陕西南秦岭柞水岩体锆石U——Pb 年龄、岩石地球化学特征及其地质意义

锆石U --Pb 定年; 柞水花岗岩; 南秦岭     

江西新余良山钼矿锆石U-Pb和辉钼矿Re-Os年龄

良山钼矿是钦杭成矿带近年发现的大中型矿床,在矿化特征分析的基础上,对其进行了成岩成矿年代学研究。采用LAICP-MS锆石U-Pb测年技术,得到矿区内石英闪长斑岩的成岩年龄为168.2±2.3Ma。通过矿床辉钼矿Re-Os同位素分析,获得其等时线年龄为168.9±1.4Ma。指示成岩作用与成矿作用同时发生,含矿热液活动与岩浆活动有密切的关系,岩浆活动可能是形成良山钼矿床的重要因素。良山钼矿床的成矿时间与钦杭成矿带内华南燕山期第一阶段大规模多金属矿化时间(170Ma)吻合。良山钼矿床形成于同一区域成矿背景下,是区域构造岩浆作用的产物,为华南燕山期成矿作用的组成部分。     

南秦岭武当群锆石SHRIMP U-Pb定年及其地质意义

武当群是南秦岭基底岩系的重要组成部分,对其时代及构造性质的研究,对认识南秦岭早期地质演化历史及其与扬子板块新元古代的相互关系具有重要的意义。目前,武当群的时代归属、划分对比还存在较大争议。本文对采自南秦岭西峡-内乡和陨西地区武当群4件变质酸性火山岩及1件侵入武当群的花岗斑岩样品进行了锆石SHRIMP U-Pb同位素定年,其中采自西峡-内乡接近武当群底部的1件火山岩样品的年龄为802±13 Ma,这一年龄可代表武当群底部地层的时代;采自该群中上部的3件火山岩样品,年龄分别为725±9 Ma、732±6 Ma和725±7Ma; 1件侵入武当群的花岗斑岩样品的年龄为703±5 Ma。根据上述结果,结合前人对武当群的研究资料,确定武当群的形成时代为810～720 Ma,相当于扬子地台板溪群;介于武当群与震旦系之间的耀岭河群可与南华系对比。     

赣南加里东期阳埠(垇子下)岩体的锆石年龄、构造背景及含矿性评价

阳埠岩体是赣南著名的含稀土岩体之一,但研究程度低,缺乏精确的同位素年代学资料。文章对阳埠岩体风化壳的锆石样品进行了激光剥蚀-多接收器电感耦合等离子体质谱(LA-MC-ICPMS)U-Pb定年,获得206Pb/238U加权平均年龄为(461.1±1.3)Ma,说明该岩体形成于中奥陶世。区域上阳埠岩体与武功山山庄岩体(461 Ma)、赣南上犹岩体(464 Ma)、云开大山花岗岩(465～467 Ma)等为同时代岩体,属华南加里东晚期第一次岩浆活动峰期产物,暗示华南加里东期褶皱造山运动的开始。结合江西省加里东期花岗岩的地球化学资料,发现多数岩体的稀土总量较高,具备成矿母岩的首要条件。今后应对南岭地区加里东期花岗岩含矿性评价及找矿工作给予重视。