稀有气体同位素对岩浆侵入方向的制约:以夏日哈木镍铜硫化物矿床为例

我国东昆仑造山带新发现的夏日哈木镍铜硫化物矿床是造山带环境产出全球镍资源最大的岩浆镍铜矿床。含矿岩体不同类型岩石中橄榄石和辉石的He、Ne和Ar同位素组成表明:~3He/~4He(0.39~0.03Ra)和~(40)Ar/~(36)Ar比值(292.0~316.9)较低,~(20)Ne/~(22)Ne和~(21)Ne/~(22)Ne沿放射性成因Ne及大陆地壳线分布,表明岩浆起源演化过程中有大陆地壳组分和大气饱和流体在橄榄石结晶前加入。He和Ar同位素混合模型计算表明岩浆中有7.8%再循环洋壳组分和87.7%大气饱和流体的加入,再循环洋壳可能带入了大气及地壳组分。~3He/~4He和~(40)Ar/~(36)Ar比值的自西向东系统性降低,以及微量元素、成矿元素和稀有气体同位素的空间协同变化特征表明地壳物质的逐步加入,即岩浆可能自西向东方向侵入,侵位过程中地壳流体的加入促使硫饱和及硫化物的熔离成矿。     

延边地区闹枝浅成热液铜金矿床稀有气体同位素地球化学特征及其成矿意义

在矿床地质和矿物流体包裹体研究的基础上,利用高真空惰性气体同位素质谱仪测定了闹枝铜金矿床硫化物中流体包裹体的稀有气体同位素组成。实验数据表明:3He/4He比值为0.033~0.104Ra,平均为0.061 Ra;20Ne/22Ne和21Ne/22Ne值分别为9.817~9.960和0.029 0~0.029 5,具有以大气组成为主的特征;40Ar/36Ar为324~349,平均为341,略高于饱和大气水(40Ar/36Ar=295.5)。流体包裹体3He/4He显示成矿流体来自壳源,不含幔源He;流体中除壳源放射性成因40Ar*外,有大气Ar的参与,放射性成因40Ar*的含量为8.8%~15.5%,平均为13.4%,大气40Ar的贡献为84.5%~91.2%,平均86.6%。结合稳定同位素特征和成岩成矿年代学研究成果,进一步厘定该矿床为相对独立的浅成中硫化型铜金矿床,成矿流体来自于年轻的大陆地壳流体,含矿流体上升过程中受到循环大气降水强烈混染作用,伴随温压条件的降低,成矿流体卸载有用元素,最终沉淀成矿。     

CCSD中HP-UHP岩石稀有气体同位素地球化学及其对板块折返过程的示踪意义

利用高真空气相质谱系统测定了CCSD中HP-UHP变质岩中主要造岩矿物流体包裹体的稀有气体同位素组成,得出其3He/4He为(0.004~0.775)×10-6,相应R/Ra为0.003~0.553,40Ar/36Ar变化较大,为316.2~11358.8,高于大气40Ar/36Ar(295.5);20Ne/22Ne和21Ne/22Ne分别为9.47~12.4和0.026~0.051,而134Xe/132Xe和136Xe/132Xe分别为0.376~0.484和0.324~0.416,均高于其相应大气值。CCSD中HP-UHP岩石主要造岩矿物的He-Ar、Xe和Ne等同位素组成清楚显示其中流体包裹体主要由地壳变质流体和少量大气饱和水组成,而深源地幔流体组分很低,其中He主要来自地壳,Ar主要由壳源放射性成因40Ar*和少量(平均32.6%)大气Ar混合组成,少量Ne和Xe可能来自地幔。CCSD中HP-UHP岩石具有F40Ar相似文献   

贵州晴隆锑矿床成矿流体He-Ar同位素地球化学

晴隆锑矿床是华南中生代低温成矿域右江盆地Au-Sb-As-Hg矿集区内的大型锑矿床,成矿时代约150Ma。本文以该矿床矿石矿物辉锑矿中的流体包裹体为测试对象,研究了成矿流体的He和Ar同位素地球化学。研究表明,成矿流体的~3He/~4He为0.13~0.46Ra(Ra为空气的3He/4He值,1.4×10~(-6)),~(40)Ar/~(36)Ar为305~327,He、Ar同位素组成具有一定程度的正相关;成矿流体由两个端元组成:一是含地壳He的低温饱和空气的雨水,二是含地幔He的高温流体。含地幔He的高温流体可能来自右江盆地下部的侏罗纪壳幔混合成因花岗岩浆,这种岩浆的形成机制与华夏地块侏罗纪与钨锡成矿有关的花岗岩具有相似性。晴隆锑矿床以大气降水为主的成矿流体的加热、循环并浸取矿床围岩"大厂层"下伏地层中的成矿元素而成矿,受深部壳幔混合成因花岗岩浆释放出的含幔源He和岩浆S的热流所驱动。     

塔里木大火成岩省瓦吉里塔格霞石岩稀有气体同位素特征及其地质意义

稀有气体被广泛用作地球化学示踪剂,本文对塔里木大火成岩省西北缘瓦吉里塔格霞石岩中的橄榄石和辉石单矿物进行了稀有气体同位素测定。结果表明,瓦吉里塔格霞石岩中的橄榄石和辉石单矿物具有较低的~3He/~4He值(分别为2.0~2.4 Ra和0.65~0.85 Ra)和略高于大气值的~(40)Ar/~(36)Ar值(342.3~651.7),反映了由古板块俯冲导致的较低的He、Ar同位素比值特征。研究表明,早中古生代南天山洋向南俯冲到塔里木板块之下,将富U或富~4He以及含有大气组分的流体带入到深部地幔,在塔里木地幔柱的作用下地幔源区发生低程度部分熔融产生霞石岩岩浆。     

新疆卡鲁安硬岩型锂矿床成矿流体性质：来自He—Ar同位素证据

卡鲁安锂矿床位于新疆北部的阿尔泰造山带,是以锂辉石为主要矿石矿物的硬岩型锂矿床。前人对该矿床的岩石成因、成矿机制及构造背景已经有了初步的认识,但对该矿区内成矿流体的研究仍是空白,这将在一定程度上影响对矿床成因的认识。本文通过分析卡鲁安伟晶岩中锂辉石和石英流体包裹体He、Ar同位素组成,对成矿流体进行示踪研究。研究表明,含矿伟晶岩的n(3He) /n(4He) 为0. 25~3.19 Ra（平均0.97 Ra）,无矿伟晶岩与外围伟晶岩n(3He) /n(4He)为0.13~5.32 Ra（平均1.13 Ra）,均介于壳源与幔源He之间。根据成矿流体的壳幔二元混合模式进行计算：含矿伟晶岩中的地幔流体比例为3.55% ~ 48.92%,平均值为14.67%;无矿伟晶岩与外围伟晶岩地幔流体占比为1.70% ~ 81.79%,平均值为17.13%。含矿伟晶岩成矿流体的n(40Ar) /n(36Ar)为552.50~13353. 00,n(40Ar*)相对含量为46.52% ~ 97.79%,平均值为87.25%,大气的Ar贡献平均为12.75%。分析结果显示,成矿流体主要以壳源流体为主,部分幔源流体和改造型饱和大气水的混合流体,随着成矿作用的进行,地幔He与大气饱和水改造Ar皆有所减少。值得注意的是卡鲁安锂矿床成矿流体中幔源物质并非真的来自于地幔物质上侵,更有可能是来源于元古代的不成熟陆壳熔融。新疆卡鲁安锂矿床形成于陆—陆碰撞造山作用晚期的后碰撞造山阶段,造山后期的伸展导致含幔源物质的古老地壳与年轻地壳减压熔融,熔融所形成的岩浆流体随后经大气降水改造为成矿流体。     

新疆卡鲁安硬岩型锂矿床成矿流体性质：来自He—Ar同位素证据

卡鲁安锂矿床位于新疆北部的阿尔泰造山带,是以锂辉石为主要矿石矿物的硬岩型锂矿床。前人对该矿床的岩石成因、成矿机制及构造背景已经有了初步的认识,但对该矿区内成矿流体的研究仍是空白,这将在一定程度上影响对矿床成因的认识。本文通过分析卡鲁安伟晶岩中锂辉石和石英流体包裹体He、Ar同位素组成,对成矿流体进行示踪研究。研究表明,含矿伟晶岩的n(3He) /n(4He) 为0. 25~3.19 Ra（平均0.97 Ra）,无矿伟晶岩与外围伟晶岩n(3He) /n(4He) 为0.13~5.32 Ra（平均1.13 Ra）,均介于壳源与幔源He之间。根据成矿流体的壳幔二元混合模式进行计算：含矿伟晶岩中的地幔流体比例为3.55% ~ 48.92%,平均值为14.67%;无矿伟晶岩与外围伟晶岩地幔流体占比为1.70% ~ 81.79%,平均值为17.13%。含矿伟晶岩成矿流体的n(40Ar) /n(36Ar)为552.50~13353. 00,n(40Ar*)相对含量为46.52% ~ 97.79%,平均值为87.25%,大气的Ar贡献平均为12.75%。分析结果显示,成矿流体主要以壳源流体为主,部分幔源流体和改造型饱和大气水的混合流体,随着成矿作用的进行,地幔He与大气饱和水改造Ar皆有所减少。值得注意的是卡鲁安锂矿床成矿流体中幔源物质并非真的来自于地幔物质上侵,更有可能是来源于元古代的不成熟陆壳熔融。新疆卡鲁安锂矿床形成于陆—陆碰撞造山作用晚期的后碰撞造山阶段,造山后期的伸展导致含幔源物质的古老地壳与年轻地壳减压熔融,熔融所形成的岩浆流体随后经大气降水改造为成矿流体。     

广西富贺钟钨锡多金属矿集区稀有气体同位素特征及其地质意义

桂东北富贺钟地区是广西重要的有色金属基地之一, 在姑婆山复式岩体的西南缘产出有新路、水岩坝和珊瑚3个主要钨锡多金属矿田。本文对不同矿田典型矿床分别开展了稀有气体同位素研究, 根据黄铁矿流体包裹体He、Ar、Ne同位素组成, 进一步讨论了区内钨锡成矿流体来源和壳-幔成矿作用过程。结果表明, 黄铁矿流体包裹体3He/4He=0.53~4.53 Ra、40Ar/36Ar=315.58~600.55、38Ar/36Ar=0.18688~0.19102、20Ne/22Ne=9.737~9.848、21Ne/22Ne=0.0291~0.0304, 显示成矿流体为地壳流体、幔源流体和饱和大气水的混合物, 成矿过程中有地幔物质的加入, 地幔He约占8.7%~75.7%。结合区内成岩、成矿的测年资料及岩石成因等综合分析认为, 区内中生代发生了多期次壳-幔相互作用, 且作用强度经历了强→弱→强的演化过程, 分别导致了姑婆山岩体主体岩性(165~160 Ma)和晚期细粒花岗岩(154~151 Ma)的侵位, 以及钨锡多金属成矿作用(136~100 Ma), 成矿与晚期的细粒花岗岩同位但不同时。     

广西栗木锡铌钽矿田成矿物质来源的惰性气体同位素示踪

文章利用黄铁矿流体包裹体惰性气体同位素,探讨了广西栗木锡铌钽矿田成矿流体的来源.黄铁矿流体包裹体的3He/4He比值为0.14～0.97 Ra,远远低于地幔流体的比值,接近饱和大气水的比值,并与地壳流体的比值处在相同的数量级上;40 Ar/36 Ar比值为555.98～ 855.11,平均705.55,显然偏离大气氩的同位素组成;40Ar*/4He比值为0.08～0.27,平均值为0.153,接近地壳值;20Ne/22 Ne=9.671～9.748和21Ne/22 Ne=0.0306～ 0.0330,具有饱和大气水的Ne同位素比值特征.结果表明,广西栗木锡铌钽矿田老虎头、牛栏岭和金竹源3个矿床的成矿流体是大气水和地壳流体的混合流体;水溪庙矿床的成矿流体也主要是大气水和地壳流体的混合流体,但可能有少量地幔流体的加入.     

赣杭构造带龙游地区早白垩世基性岩矿物化学、岩石地球化学特征及其地质意义

通过龙游晚中生代基性岩岩相学观察、全岩主量、微量元素和Sr-Nd同位素及矿物电子探针分析,对岩石成因、岩浆演化和构造环境进行探讨。龙游基性岩岩性为橄榄辉长岩,Sr-Nd同位素显示为幔源特征;主量、微量元素特征显示其经历了以橄榄石、辉石为主的分离结晶作用,且未发生明显的地壳物质混染。橄榄石颗粒具核-边结构,富Mg贫Fe的核部Fo值为90.1～91.8,指示原始岩浆是软流圈地幔,富Fe贫Mg的边部显示橄榄石Fo值为77.4～85.3,且核-边两部分的Fo值相差较大,显示原始橄榄石形成之后受到地幔熔体/流体的交代作用。辉石斑晶大多属于透辉石,在部分斑晶的边部发育少量霓辉石。透辉石斑晶普遍具有核-幔-边结构,从核部到边部的SiO_2含量降低,TiO_2、Al_2O_3含量升高,结晶温度升高,显示原始辉石形成之后受到温度更高的地幔熔体/流体的交代作用。研究认为,古太平洋板块后撤造成岩石圈地幔拉伸作用并形成赣杭构造带深部断裂后,部分软流圈物质受到地幔流体/熔体的交代作用,并沿这些深部断裂向上侵位,经历了以橄榄石和辉石矿物为主的分离结晶作用和微弱的地壳物质混染,最终形成龙游橄榄辉长岩。     

粤北诸广南部铀矿田流体包裹体的氦氩同位素组成及成矿流体来源示踪

粤北诸广南部铀矿田是我国重要的花岗岩型铀矿产地之一,有关诸广南部花岗岩型铀矿田的成因,多年来一直存在较大的争议。本文以诸广南部铀矿田典型铀矿床成矿期萤石、方解石和黄铁矿中流体包裹体为测试对象,研究了成矿流体的He、Ar同位素地球化学。研究表明,萤石流体包裹体的~3He/~4He比值为0. 021～0. 186Ra,~(40) Ar/~(36)比值为298. 4～2515. 7;方解石流体包裹体的3He/4He比值为0. 027～0. 209Ra,~(40) Ar/~(36)比值为295. 9～327. 2;黄铁矿流体包裹体的3He/4He比值为0. 021～1. 543Ra,~(40) Ar/~(36)比值为326. 9～1735. 1; He-Ar同位素系统显示成矿流体的3He/4He比值略高于地壳氦同位素特征值(0. 01～0. 05Ra),但低于幔源氦同位素特征值(6～9Ra),~(40) Ar/~(36)比值接近或高于大气氩的同位素组成(~(40) Ar/~(36)=295. 5),成矿流体为壳-幔混合来源。结合H-O、He-Ar、C和Sr等多元同位素证据表明,成矿流体由两个端元组成:一是含有一定放射性成因Ar的大气降水的地壳流体,二是含幔源He的地幔流体。进一步研究表明,受NNW向断裂控制的棉花坑、书楼丘、长排等铀矿床受地幔流体影响比较大,而受NE向断裂控制的蕉坪、东坑、烟筒岭铀矿床受大气降水影响比较大。     

Mantle-derived noble gases in ore-forming fluids of the granite-related Yaogangxian tungsten deposit,Southeastern China

More than 90% of the tungsten resources of China are in the Nanling region of South China, and the Yaogangxian vein deposit is the largest tungsten deposit in this region. The tungsten deposits have ages of 150–160 Ma, and are spatially, temporally and genetically related to granites which were previously believed to be produced by crustal anatexis. This paper provides He and Ar isotope data of fluid inclusions in pyrite and arsenopyrite from the Yaogangxian W veins. ³He/⁴He ratios range from 0.41 to 3.03 Ra (where Ra is the ³He/⁴He ratio of air?=?1.39?×?10^?6), and ⁴⁰Ar/³⁶Ar ratios from 328 to 1,191. Moreover, there are excellent correlations between He and Ar isotopic compositions. The results suggest that the ore-forming fluids are a mixture between a crustal fluid containing atmospheric Ar and crustal ⁴He and a fluid containing mantle components. It is likely that the former is a low temperature meteoric fluid, and the later is a fluid exsolved from the W-associated granitic magma, which formed by crustal melting induced by intrusion of a mantle-derived magma.     

内蒙古哈达门沟金矿成矿流体来源的氦、氩同位素示踪

内蒙古包头市哈达门沟金矿床是华北陆块北缘乌拉山-大青山地区的大型金矿床,矿床赋存于新太古界乌拉山群黑云角闪斜长片麻岩、角闪黑云二长片麻岩和含石榴石黑云斜长片麻岩中,成矿流体性质不明。文章对哈达门沟金矿主要载金矿物黄铁矿开展了流体包裹体中的He、Ar同位素组成研究。研究表明,赋存于黄铁矿流体包裹体中的4He含量为(83.92~606.46)×10-8cm3STP/g,n(3He)/n(4He)值为0.19~0.91Ra,幔源He的含量为2.62%~13.73%,平均为9.95%,表明成矿流体中的He主要来源于地壳,大约10%来源于地幔。~(40)Ar含量为(71.22~308.22)×10~(-8)cm~3STP/g,~(40)Ar/~(36)Ar比值变化于2793.6~7253.5之间,在n(~(40)Ar)/n(~(36)Ar)与R/Ra图解和n(~(40)Ar*)/n(4He)与R/Ra图解中,显示地壳氩和地幔氩的混合来源特征。结合已有的氢、氧、硫同位素研究,认为哈达门沟金矿成矿流体主体为地壳来源,但幔源流体的加入清晰可辨,乌拉特前旗-呼和浩特山前断裂很可能为富钾质壳幔混合流体的运移提供了通道和动力。     

新疆坡北杂岩体西端镁铁-超镁铁质岩体成因的稀有气体同位素制约

新疆坡北镁铁-超镁铁质杂岩体由一个辉长岩体以及二十多个超镁铁质侵入体组成,其中坡一超镁铁质岩体稀有气体同位素组成揭示存在地幔柱的贡献。坡北杂岩体西端的坡一、坡四、坡十和坡十四等几个超镁铁质岩体的稀有气体同位素对比分析结果表明,岩浆矿物的³He/⁴He值（0.26~2.79Ra）分布于地壳与地幔值之间,较高的²⁰Ne/²²Ne和较低的²¹Ne/²²Ne值分布于Ne质量分馏线（MFL）和L-K线之间,⁴⁰Ar/³⁶Ar=295~598。³He/⁴He与⁴⁰Ar/³⁶Ar比值揭示坡北杂岩体西端不同超镁铁质岩体形成过程中地幔（柱）、地壳和大气组分的贡献不同,岩体成因也可能不同。其中,坡一岩体具有地幔柱作用的贡献,其他三个岩体的岩石圈地幔及地壳流体组分的贡献较大。岩浆地幔源区由深部地幔柱物质叠加俯冲流体交代的岩石圈地幔物质所组成,大气与地壳物质组分可能由俯冲再循环洋壳带入到岩浆地幔源区以及围岩物质的混入。     

Magma mixing and gold mineralization in the Maevatanana gold deposit,Madagascar

The Maevatanana gold deposit in Madagascar is hosted by Archean metamorphic rocks in quartz–sulfide veins that are structurally controlled by NNW–SSE trending shear zones. Fluid inclusion data show that the trapping conditions in quartz range from 0.87 to 2.58 kbar at temperatures of 269–362 °C. Laser Raman spectroscopy confirms that these inclusions consist of CO₂, SO₂, and H₂O. The δ³⁴S values of the pyrites range from 1.7‰ to 3.6‰, with an average of 2.25‰, supporting a magmatic origin. Noble gases (He, Ne, Ar, Ke, Xe) are chemically inert, thus will not be involved in chemical reactions during geological processes. Also due to the low concentration of He in the atmosphere and the low solubility of He in aqueous fluids, the atmosphere-derived He is unlikely to significantly affect He abundances and isotopic ratios of crustal fluids, ensures that He production should have the typical crust ³He/⁴He ratios. The ³He/⁴He ratios of fluid inclusions in pyrite from the deposit range from 0.06 to 0.12 Ra, while the ⁴⁰Ar/³⁶Ar ratios range from 6631 to 11441. We infer that the ore-forming fluids could have been exsolved from a granitic magma. The oxygen and hydrogen isotope compositions of the ore-forming fluids (1.5‰ ≤ δ¹⁸O_H2O ≤ 7.8‰; –72‰ ≤ δD ≤ –117‰) indicate they were derived from a granitic magma. Four pyrite samples from the gold deposit yield a precise Re–Os isochron age of 534 ± 13 Ma. Given that the post-collisional granites in northern and central Madagascar were derived by melting of sub-continental lithospheric mantle and formed between 537 and 522 Ma, we can state that the gold metallogenesis was coeval with the crystallization age of these parental magmas. These data could be accounted for the formation of the Maevatanana gold deposit. First, the shear zones hosting the deposit formed around 2.5 Ga, when the Madagascan micro-continental blocks collided with other continental blocks, triggering large-scale tectono-magmatic activity and forming NNW–SSE trending shear zones. The gold mineralization at Maevatanana is coeval with the crystallization age of the Cambrian post-collisional A-type granitoid plutons in northern and central Madagascar, implying that this deposit is associated with extensional collapse of the East African Orogen. This extension in turn induced asthenospheric upwelling, melting of sub-continental lithospheric mantle. These magmas underplated the lower crust, generating voluminous granitic magmas by partial melting of the lower crust. The mixing magma during tectono-thermal reactivation of the East African Orogen produced large volumes of volatiles that extracted gold from the granitic magma and produced Au–S complexes (e.g., Au(HSO₃)²⁻). The shear zones, which were then placed under extensional collapse of the East African Orogen in the Cambrian, formed favorable pathways for the magmatic ore-forming fluids. These fluids then precipitated gold-sulfides that form the Maevatanana gold deposit.     

The Isotopic Composition of Noble Gases in Gold Deposits and the Source of Ore- Forming Materials in the Region of North Hebei, China

1IntroductionOnthenorthernmarginoftheNorthChinaplatformislocatedoneofthemostimportantAu Ag polymetallicore concentratedzones,wherethereareavarietyoforetypes .Soithasbeenat tractingeverincreasingattentionofmanygeologists (PeiRongfuetal.,1 998;ShenBaofengetal.,1 994 ;LuSongnianetal.,1 997;HuShouxietal.,1 994 ;ChenYuchuan ,1 999;ZhaiYushengetal.,1 999) .Manyscholarspresentedtheirresearchresultsinvariousaspects.How ever ,thesourceofore formingmaterialshaslongbeenafocusofdiscussion .Studieso…     

Noble gas isotopic systematics of Fe-Ti-V oxide ore-related mafic-ultramafic layered intrusions in the Panxi area, China: The role of recycled oceanic crust in their petrogenesis

Olivine and clinopyroxene grains have been separated from four large Fe-Ti-V oxide ore-bearing intrusions (Panzhihua, Hongge, Baima and Taihe) in the Panxi area, Emeishan large igneous province, Southwest China, for He and Ar isotope studies. The samples examined revealed extremely low ³He/⁴He ratios (0.078-4.34 Ra with the mean value 0.78 Ra) for gases extracted by stepwise heating. This feature, combined with low ⁴⁰Ar/³⁶Ar ratios can be interpreted as due to addition of subduction-related fluids and melts that had been stored in the lithospheric mantle for long periods. Considering the regional geologic history, such addition can be attributed to the paleo subduction that occurred along the western margin of the Yangtze Block during the Neoproterozoic. The subducted oceanic crust beneath the Panxi area underwent eclogite-facies metamorphism and subsequent exhumation. The infiltration of subduction-related melts and fluids into the lithospheric mantle led to enriched isotopic signatures from that of the slightly depleted asthenopheric mantle which has been suggested by the Sr, Nd and Pb isotopic data of the Emeishan basalts and picrites. In addition, considerable amounts of eclogitic melts produced by partial melting of eclogite-facies oceanic crust extensively contaminated the lithospheric mantle. During the late Permian, partial melting of an upwelling mantle plume that contained an eclogite or pyroxenite component generated the parental Fe-rich magma that supplied the ore-bearing intrusions. The combination of these factors may have been the crucial reason that many world-class Fe-Ti-V oxides deposits are clustered in the Panxi area.