黔东南从江那哥铜多金属矿床成矿流体来源的S-H-O同位素制约

从江那哥铜多金属矿床位于扬子陆块与华夏陆块过渡带上的江南造山带西南段,是本区多金属矿床的典型代表。为确定矿床的成矿流体来源,本文利用连续流动质谱和MAT-253等先进分析设备系统研究了矿床的S-H-O同位素组成。矿石硫化物的δ34SV-CDT值介于-2.7‰～2.8‰之间,均值为0.1‰,多数集中在-2.5‰～2.5‰之间,具有幔源硫特征,暗示成矿物质中硫来源于深部幔源;脉石石英包裹体的δDV-SMOW和δ18OH2O值,分别介于-60.7‰～-44.4‰之间和7.9‰～9.0‰之间,在δD和δ18O图解中,全部样品落入岩浆水和/或变质水范围内。S、H和O同位素结果表明存在地幔流体参与成矿,其赋矿浅变质沉积岩地层也为成矿提供了部分成矿流体。综合研究认为该矿床成矿流体具有多来源特征。     

新疆萨喀尔得铜矿C-H-O-S同位素特征

新疆萨喀尔得铜矿属中低温热液型,该矿石英和方解石样品中^δ13CPDB值为-17．3‰— -0．7％,δ^18OSMOW为16．2‰-22．4‰ δ18OH2O 水值为6.9‰-12.5‰水值为6．9‰-12．5‰,8D变化于-73．8‰—-52．4‰之间。研究表明,成矿流体主要来源于深部发生循环加热的建造水,并混合变质水和岩浆水;成矿早期流体中的C主要来源于地层水或大气降水,晚期有深部岩浆水的加入。^δ^34S值变化范围为0．2‰-6．1％o,表明流体中的S主要来自岩浆或上地幔。     

攀西大陆槽稀土矿床深源成矿流体的稳定同位素证据

通过对大陆槽矿床的成矿流体稳定同位素研究表明,矿体石英中流体包裹体的δD、δ^18O和δ^13C值分别为-87‰、 6．0‰和-8．4‰,矿石(氟碳铈矿)的δ^13C为-8．0‰,矿体萤石中流体包裹体的δD和δ^18O分别为-99‰和-11．6‰。研究表明,矿床的成矿流体应为少量大气降水混合的深源成矿流体,流体包体中和矿石中的碳则可能源自较深的壳幔混熔源区。     

赣南西华山钨矿床的流体混合作用:基于H、O同位素模拟分析

赣南西华山钨矿床是我国典型的大型石英脉型黑钨矿矿床.H、O同位素的研究表明,该矿床δD值-43‰～-66‰,石英δ18O值2.3‰～13.2‰,对应的成矿流体δ18O值-8.7‰～7.6‰,表明成矿流体为岩浆水与大气降水的混合流体.不同机制下矿物O同位素模拟计算表明,冷却、沸腾和混合作用所形成矿物的O同位素组成明显不同...     

豫西公峪金矿床地质地球化学特征及成因探讨

文章较为详细地总结了公峪蚀变岩型金矿的地质特征，将成矿作用分为3个阶段，即石英-黄铁矿阶段，石英-硫化物阶段和石英-碳酸盐阶段，并测定了矿石样品的稳定同位素组成。结果表明：硫化物的δ^34S值变化于-1．7‰～2．2‰之间，与陨石硫的δ^34S值接近，反映为深源；成矿Ⅰ阶段流体的δD值为-68‰--86‰，δ^18OH2O为-0.6‰～ 4．9‰，成矿Ⅱ阶段流体的δD值为-67‰～-84‰，δ^18OH2O为-0．6‰～-8．9‰，反映成矿流体主要有两个来源，Ⅰ阶段以深源水为主，Ⅱ阶段有大量大气降水混入。公峪金矿与祁雨沟金矿应属于同一成矿系统的产物，均与燕山晚期岩浆热液活动有关，可能为同源、同期、不同构造空间的演化产物。     

老挝帕奔金矿床同位素地球化学特征

对矿床热液成矿期含金方解石中H、O、C稳定同位素测定,探讨主成矿期成矿流体和成矿物质来源,为深入研究帕奔金矿成矿机制、成矿作用提供了新的地球化学资料。含金方解石碳氧同位素~(13)C_(V-PDB)值分布在-4.5‰~-5.2‰之间,~(18)O_(V-SMOW)值分布于20.0‰~20.8‰之间,含金的方解石矿物来源为流体与二叠纪海相碳酸盐岩相互作用产物;含金方解石矿物中包裹体水的δD值在-49‰~-92‰之间,δ~(18)O-H_2O的范围为8.32‰~13.42‰,成矿流体来源与岩浆活动存在密切关系。     

新疆萨喀尔得铜矿C-H-O-S同位素特征简

新疆萨喀尔得铜矿属中低温热液型,该矿石英和方解石样品中δ13CPDB值为-17.3‰~-0.7‰,δ18OSMOW为16.2‰~22.4‰,δ18OH2O水值为6.9‰~12.5‰,δD变化于-73.8‰~-52.4‰之间。研究表明,成矿流体主要来源于深部发生循环加热的建造水,并混合变质水和岩浆水;成矿早期流体中的C主要来源于地层水或大气降水,晚期有深部岩浆水的加入。δ34S值变化范围为0.2‰~6.1‰,表明流体中的S主要来自岩浆或上地幔。     

鲁西平邑归来庄金矿床成矿流体研究

对鲁西平邑地区归来庄金矿成矿晚阶段蚀变矿物方解石的流体包裹体和稳定同位素进行了详细的研究后发现：保存于方解石脉中的包裹体均为气液两相盐水溶液，均一温度在110℃～250℃之间，冰点变化于-2．8℃～-9．3℃之间，对应的盐度在4．65％～13．18％之间。同位素研究结果显示：矿床的δ^34S值介于-0．71‰～2．990‰之间，δ^13CPDB值为-3．3‰～0．0‰，δDSMOW为-48‰～-61‰，δ^18O水值在-1．13‰～5．07‰之间。硫同位素研究表明成矿流体来源于地幔，碳、氢、氧同位素则显示有较多的大气降水混入。锆石SHRIMP测年结果暗示归来庄金矿形成于中侏罗世，其成因与角砾岩体的隐爆、流体的减压沸腾和深循环的古大气水混入有关。     

柿竹园钨多金属矽卡岩-云英岩与铅锌银矿脉C、H、O、Pb同位素地球化学研究

柿竹园W_Sn_Mo_Bi_Pb_Zn_Ag矿田是南岭地区典型多金属矿田,其具有显著的蚀变_成矿分带特征:近接触带矽卡岩-云英岩型W_Sn_Mo_Bi矿床(如柿竹园、金船塘、柴山地区)和远接触带脉状Pb_Zn_Ag矿床(如蛇形坪、横山岭、百步窿、枞树板地区)。通过对远—近接触带中主要蚀变岩石和矿石样品的C、H、O、Pb同位素研究,发现在近接触带块状矽卡岩中方解石的δ~(13)C和δ~(18)O值分别在-6.5‰~-3.6‰和4.8‰~8.4‰之间,远接触带Pb_Zn_Ag矿脉中团块状和脉状方解石的δ~(13)C和δ~(18)O值分别在-3.5‰~-1.5‰和8.1‰~15.8‰之间,表明矽卡岩形成于岩浆热液流体的渗滤交代作用,而远接触带碳酸盐脉的形成与热液流体沿灰岩裂隙充填过程中的水岩反应相关。近接触带块状云英岩中石英的δD_(H_2O)和δ_(18)O_(H_2O)值分别为-77‰和5.1‰,矽卡岩中石榴子石的δD_(H_2O)值为-97‰,δ_(18)O_(H_2O)值范围在9.2‰~9.4‰,网脉状云英岩中石英的δD_(H_2O)和δ_(18)O_(H_2O)值分别为-83‰和-8.2‰,退化蚀变矽卡岩中石英的δD_(H_2O)和δ_(18)O_(H_2O)值分别为-65‰和-4.2‰,远接触带石英脉中石英样品的δD_(H_2O)和δ_(18)O_(H_2O)值分别为-83‰和2.8‰,表明近接触带的块状矽卡岩和云英岩与远接触带石英脉成矿流体具有岩浆水的特征,而网脉状云英岩和退化蚀变矽卡岩成矿流体具有岩浆流体与大气水混合的特征。远—近接触带中方铅矿的206Pb/204Pb值范围18.565~18.622,207Pb/204Pb值范围15.694~15.738,208Pb/204Pb值范围38.819~38.986,表明Pb等金属元素来源于上地壳。     

云南巍山—永平碰撞造山带走滑拉分盆地铜金多金属矿成矿流体系统：稳定同位素特征及热液来源

云南巍山—永平矿集区位于兰坪走滑拉分盆地南段,有铜金多金属中、小型矿床及矿化点140余处,盆地发育和成矿作用与印度—亚洲板块碰撞密切相关。为了探索该矿集区成矿热液的来源,研究了该区成矿流体的稳定同位素特征。区内成矿流体系统可分为紫金山子系统与公郎弧子系统。公郎弧子系统内铜钴矿床成矿流体的δD为-83.8‰~-69‰,δ18O为4.17‰~10.45‰,δ13C为-13.6‰~3.7‰,成矿流体主要来源于岩浆水及地层水。紫金山子系统内金、铅锌、铁矿床成矿流体的δD为-117.4‰~-76‰,δ18O为5.32‰~9.56‰,δ13C为-10.07‰~-1.5‰;锑矿成矿流体的δD为-95‰~-78‰,δ18O为4.5‰~32.3‰,δ13C为-26.4‰~-1.9‰,成矿流体来源于地层水以及岩浆水。受印度板块与亚洲板块碰撞造山作用的影响,在该盆地内,成矿流体自南西向北东大规模迁移过程中,先形成温度、盐度较高的公郎弧子系统,随着流体向北东推进,温度、盐度逐渐降低,流体成分发生变化,演变为紫金山子系统。     

Police, politics, and the right to the city

Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete.     

Isotopic systematics of He,Ar, S,Cu, Ni,Re, Os,Pb, U,Sm, Nd,Rb, Sr,Lu, and Hf in the rocks and ores of the Norilsk deposits

This paper reports the first results of a study of 11 isotope systems (³He/⁴He, ⁴⁰Ar/³⁶Ar, ³⁴S/³²S, ⁶⁵Cu/⁶³Cu, ⁶²Ni/⁶⁰Ni, ⁸⁷Sr/⁸⁶Sr, ¹⁴³Nd/¹⁴⁴Nd, ^206–208Pb/²⁰⁴Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others.     

Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean

The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological (i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates) controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were <20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is lost to sediments.     

Composition,formation conditions,and genesis of the Talatui gold deposit,the Eastern Transbaikal Region,Russia

The mineral composition of the Talatui gold deposit has been studied with modern methods. Previously unknown minerals (ilmenite, siegenite, glaucodot, wittichenite, matildite, hessite, pilsenite, zircon, tremolite, cummingtonite, hercynite, and goethite) have been identified in the ore. A high Re content has been detected in molybdenite. The spatiotemporal separation of Au and Ag is caused by different mineral species of these elements and their diachronous precipitation during the ore-forming process. Gold crystallized along with early mineral assemblages, beginning from virtually pure gold (the fineness is 996). Silver precipitated largely at the end of the process as hessite (Ag₂Te) and matildite (AgBiS₂). The temperature of ore deposition varied from 610 to 145°C, the pressure was 3370–110 bar, and the salt concentration ranged from 56.3 to 0.4 wt % NaCl equiv. The heterogeneous state (boiling) of fluid at the early stages has been documented. The chemical and isotopic compositions of the fluid testify to its magmatic nature and the participation of meteoric water at late stages in the ore-forming process. Thermodynamic modeling reproduces the main specific features of ore formation, including separation of Au and Ag. A physicochemical model of the gold mineralization in the Darasun ore district has been proposed. On the basis of several attributes, the Talatui deposit has been referred to the prophyry gold-copper economic type.     

Rb-Sr, K-Ar, H-and O-Isotope systematics of the Middle Riphean shales from the Debengda Formation, the Olenek Uplift, North Sibera

Clay subfractions (SFs) of <0.1, 0.1–0.2, 0.2–0.3, 0.3–0.6, 0.6–2 and 2–5 μm separated from Middle Riphean shales of the Debengda Formation are studied using the TEM, XRD, K-Ar and Rb-Sr isotopic methods. The oxygen and hydrogen isotope compositions in the SFs are studied as well. The low-temperature illite-smectite is dominant mineral in all the SFs except for the coarsest ones. The XRD, chemical and isotopic data imply that two generations of authigenic illite-smectite different in age are mixed in the SFs. The illite crystallinity index decreases in parallel with size diminishing of clay particles. As compared to coarser SFs, illite of fine-grained subfractions is enriched in Al relative to Fe and Mg, contains more K, and reveals higher K/Rb and Rb/Sr ratios. The Rb-Sr age calculated by means of the leachochron (“inner isochron”) method declines gradually from 1254-1272 Ma in the coarsest SFs to 1038-1044 Ma in finest ones, while the K-Ar age decreases simultaneously from 1225–1240 to 1080 Ma. The established positive correlation of δ¹⁸O and δD values with dimensions of clay particles in the SFs seems to be also consistent with the mixing systematics. The isotopic systematics along with data on mineral composition and morphology lead to the conclusion that mixedlayer illite-smectite was formed in the Debengda shales during two periods 1211–1272 and 1038–1080 Ma ago. The first period is likely close to the deposition time of sediments and corresponds to events of burial catagenesis, whereas the second one is correlative with the regional uplift and changes in hydrological regime during the pre-Khaipakh break in sedimentation.     

Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA

Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N₂ in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area.     

扬子北缘马元铅锌矿床闪锌矿微量元素及S-Pb-He-Ar-C同位素地球化学研究

马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多1000,成矿温度以中-低温为主。金属硫化物ε~(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,~(206)Pb/~(204)Pb为17.858~17.918:~(207)Pb/~(204)Pb为15.603~15.694;~(208)Pb/~(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra~1.05Ra,~(40)Ar/~(36)Ar为326.1~765.1,~(38)Ar/~(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ~(13)C_(CH_4)值为-36.01‰~-28.80‰,δ~(13)C_(C_2H_6)值为-27.72‰~-22.44‰,δ~(13)C_(CO_2)值为-23.24‰~-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。     

Sedimentary structures in the Lower Greensand of the Weald,England, and Bas-Boulonnais,France

Study of the cross-stratification and other sedimentary structures in the Lower Greensand of the Weald, England, and Bas-Boulonnais, France, indicates that the sediments were deposited by the lateral migration of sand waves in a neritic sea. Comparison of the Lower Greensand sea with the modern North Sea was attempted. If those sediments were deposited as a result of tidal current similar to the present-day North Sea then the Lower Greensand shoreline could be deduced as running northwest-southeast, indication that the western part of the London Platform was submerged.     

山西五台山区滹沱群变质玄武岩岩石学、地球化学特征及其成因意义

在野外地质调查的基础上,选取滹沱群豆村亚群底部四集庄组玄武岩、顶部青石村组玄武岩和东冶亚群中下部河边村组玄武岩,进行岩石学和地球化学研究。分析结果表明：玄武岩主量元素高TiO2、TFeO,低MgO,具有演化的基性岩浆的特征。稀土元素含量相对较高,具有弱—中等程度的轻稀土元素富集,中等程度的轻重稀土元素分异,轻微的Eu异常;玄武岩中Cr、Ni含量变化较大,但与Mg#具有很好的正相关性。微量元素配分图解中具有明显的Sr负异常,部分样品具有Nb、Ta和Ti负异常,无Zr、Hf负异常,与岛弧火山岩不同;同时Nb、Ta无分异,Zr/Hf值较高,具有板内玄武岩浆的特征。综合分析认为,滹沱群玄武岩可能形成于板内裂谷环境。在岩浆上升过程中发生橄榄石与尖晶石的分离结晶作用,同时不同程度地受到地壳的混染。