Origin of ore fluids in the Muruntau gold system: Constraints from noble gas, carbon isotope and halogen data   总被引：6，自引：0，他引：6  

Torsten Graupner  Samuel Niedermann  Reiner Klemd  Achim Bechtel 《Geochimica et cosmochimica acta》2006,70(21):5356-5370

Hydrothermal vein minerals directly associated with native gold mineralization in the Muruntau vein system (Uzbekistan) have been studied for noble gas, carbon isotope and halogen chemistry of the trapped ore-related fluids. Helium trapped in early arsenopyrite 1, which has preserved the original fluid signature better than associated scheelite and quartz, indicates a small input from a mantle source (?5% of total He). However, the overwhelming majority of the He in the fluid (∼95%) is from crustal sources. The noble gases Ne, Kr and Xe in the sample fluids are dominated by gases of atmospheric origin. The carbon isotope (δ¹³C: −2.1‰ to −5.3‰) and halogen characteristics of the fluids (log Br/Cl: −2.64 to −3.23) lend further support for the activity of juvenile fluids during the main ore stage. The high proportion of crustal components in the ore-forming fluids may be explained by intense fluid-rock interaction and is also supported by previous Nd and Sr isotope studies. The involvement of a juvenile fluid component during the main stage of hydrothermal activity at Muruntau (∼275 Ma) can be linked to the emplacement of lamprophyric dikes at Muruntau, due to apparently overlapping ages for high-temperature alteration, related ore vein formation and intrusion of the dikes. The input of mantle-derived fluids, possibly related to the Hercynian collisional event in the western Tien Shan, stimulated intense fluid-rock interaction in the crust. In this context, the mantle-derived fluid should be considered as one possible carrier of metals. Significant amounts of external meteoric fluids circulating in fracture systems are interpreted to have modified the noble gas signature of fluid in quartz, mostly during late, low temperature fluid circulation.  相似文献   

P-T evolution and fluid inclusion characteristics of retrograded eclogites,Münchberg Gneiss Complex,Germany     

Reiner Klemd 《Contributions to Mineralogy and Petrology》1989,102(2):221-229

Kyanite eclogites occur as part of the Münchberger nappe pile in NE-Bavaria, West Germany. Eclogites are overprinted by subsequent amphibolite facies metamorphism. The preservation of primary eclogitic textures as well as symplectitic textures are indicative of rapid decompression. Eclogite formation is estimated to have occurred under conditions of high H₂O-activities at pressures between 20 and 26 kbar and temperatures ranging between 590 and 660° C, as is shown by the coexistence of omphacite (Jd 50), kyanite, zoisite and quartz. Minimum pressure estimates, independent of the water activity, range between 9 and 16 kbar at the relevant temperatures. Detailed studies of fluid inclusion reveal two predominant groups of aqueous-brine inclusions: high salinity (14–17 wt% NaCl equiv.) and low salinity (0–8 wt% NaCl equiv.) inclusions. Fluid compositions of both groups of inclusions yield isochores passing close to the estimated amphibolite facies PT-field. The compositions of these fluids are in good agreement with fluid compositions considered from mineral equilibria. None of the fluid inclusions has densities appropriate for eclogite facies metamorphism, but probably reflect later amphibolite facies metamorphism.  相似文献   

The rare alkalies in hydrothermal alteration at Wairakei and Broadlands,geothermal fields,N.Z.     

Reiner Goguel 《Geochimica et cosmochimica acta》1983,47(3):429-437

Drillcores and waters from Wairakei and Broadlands geothermal areas New Zealand have been analyzed for Li, Rb, Cs, Na, K, Mg, Ca, Al, Ti, Mn, and Be. The drillcores were altered to various degrees at temperatures below 300°C in slightly alkaline chloride water, probably derived from rock-water interaction in untapped horizons at higher temperature. It changes its composition as it leaches Ca and Na from the rock and adds K, Rb, Cs and Li. Evaluation of these changes in relation to the dimensions of the altered zone under observation suggests that a high mass ratio of water to rock (e.g., 100) and a period of up to 1 million years are responsible for the present stage of alteration.Increase of K and Rb in the altered rocks is a result of the formation of abundant adularia in addition to illite. The $\text{K}\text{Rb}$ ratio of the rock decreases during alteration but remains higher than that of the fluid. Only clay materials and zeolites that preferentially absorb Rb give slightly lower $\text{K}\text{Rb}$ ratios than the fluid.The mineral phases responsible for the uptake of lithium during alteration are chlorite (300 ppm Li) and quartz (up to 430 ppm Li). Li uptake in quartz is considered to be the mechanism by which Al-rich quartz crystallises from alumino-silicates. $\text{Li}\text{Al}$ atomic ratios of 0.3–0.57 and Al concentrations up to 3000 ppm have been observed.Relatively small concentrations of Cs are found in potassic minerals (e.g. 10 ppm Cs in adularia, 44 ppm Cs in illite). However, 240 ppm Cs are found in wairakite from Wairakei equilibrated at 235°C. Lower equilibration temperatures may lead to higher cesium concentrations. This effect, in conjunction with a more concentrated hydrothermal fluid, could explain a content of 4500 ppm Cs in wairakite extracted from a drillcore taken in the El-Tatio geothermal field in Chile.  相似文献   

Determination of the distribution of size of irregularly shaped particles from laser diffractometer measurements     

Claudio L. Schneider  Reiner Neumann  Alan S. Souza 《International Journal of Mineral Processing》2007

The formal stereological transformation equation for particle sieve size distribution from measurements in lower dimensional spaces is applied to laser diffractometer measurements. The transformation function for iron ore particles is measured experimentally, and modeled. The solution is tested against the measured transformation function data as well as synthetic composite distributions of the original sample. The natural size distribution of a sample taken from a grinding circuit stream was measured by a combination of standard sieving and cyclosizer, and the result is compared to the transformed size distribution calculated from laser diffractometer measurements. The stereological transformation technique performed well in all cases.  相似文献   

西天山榴辉岩石榴石中的水及其分布特征     

苏文  高俊  Reiner  KLEMD  熊贤明 《岩石学报》2006,22(5):1380-1386

运用电子探针和显微Fourier变换红外光谱技术，对新疆西天山3个榴辉岩样品中的石榴石进行了详细的主量元素和结构水分析。结果显示，石榴石发育以核部富锰铝榴石组分、边部富镁铝榴石组分进变质作用的成分环带。石榴石中OH^-1分布也具有规律：核部→边缘。其结构水OH^-1逐步增加，即从核部的89-239ppm增加到边部的367-658ppm；与石榴石边部相比，石榴石的核部含有较低的OH^-1，却含有较高的H2O和Mn含量。这表明，在蓝片岩向榴辉岩进变质作用过程中，含水矿物脱水反应而释放出大量的分子水，这部分水促进了高压变质反应，形成榴辉岩相矿物，石榴石核部的结晶就是在富水和Mn的条件下进行的。随着高压变质作用的继续，石榴石核部的分子水逐步失水而进入石榴石晶格，形成结构水。因此，在高压变质作用过程中，OH^-1演化实际上是一个由内部不平衡逐步向平衡转变过程。P588．348  相似文献   

Fluid inclusion studies of the Abawso gold prospect,near the Ashanti Belt,Ghana   总被引：1，自引：0，他引：1  

Sven?E.?WilleEmail author  Reiner?Klemd 《Mineralium Deposita》2004,39(1):31-45

The major Ghanaian lode gold deposits are preferentially aligned along the western and eastern contacts of the Kumasi Basin with the Ashanti and Sefwi Belts, respectively. The investigated area of the Abawso small-scale concession, covering the workings of the old Ettadom mine, is situated 3 km west of the lithological contact of the Birimian metavolcanic rocks of the Akropong Belt in the east with the Birimian metasedimentary rocks of the Kumasi Basin in the west. The rocks of the Abawso concession represent a steeply NW-dipping limb of a SE-verging anticline with an axis plunging to the SW. Quartz veining occurs predominantly in the form of en échelon dilatational veins along NNE–SSW-striking shear zones of a few metres width and shows evidence of brittle and ductile deformation. Also stockwork-style quartz veining occurs in the vicinity of the main shaft of the old Ettadom mine. Hydrothermal alteration includes sericitisation, sulphidation and locally carbonatisation. The auriferous quartz veins mainly follow the trend of brittle to ductile deformed quartz veins; however, some occur in stockwork. Fluid inclusion studies reveal a large number of H₂O inclusions along intragranular trails in auriferous quartz vein samples, as well as an overall dominance of H₂O and H₂O-CO₂ inclusions over CO₂ inclusions. Textural observations and physico-chemical fluid inclusion properties indicate post-entrapment modifications for all quartz vein samples due to grain boundary migration recrystallisation. This process is interpreted to be responsible for the generation of the CO₂ inclusions from a H₂O-CO₂ parent fluid. In comparison with mineralisation at the Ashanti and Prestea deposits, which are characterised by CO₂±N₂ inclusions, the observed inclusion assemblage may be due to a shallower crustal level of mineralisation, or different degrees and styles of recrystallisation, or a less pronounced development of laminated quartz veins due to comparably restricted pressure fluctuations. Furthermore, the microthermometric observations allow the reconstruction of a possible retrograde P-T path, depicting near-isothermal decompression in the P-T range of the brittle/ductile transition.Editorial handling: E. Frimmel  相似文献   

Gravity field contribution analysis of GOCE gravitational gradient components   总被引：4，自引：0，他引：4  

Weiyong Yi  Reiner Rummel  Thomas Gruber 《Studia Geophysica et Geodaetica》2013,57(2):174-202

A gravity field model is computed from the four accurate gravitational gradient components of GOCE (Gravity field and steady-state Ocean Circulation Explorer), combined with the analysis of the kinematic orbits, and some moderate constraint (or stabilization) in the polar areas where no observation from GOCE is available due to the orbit geometry. The normal matrix of each component is computed individually in order to study its contribution to the combined solution. The results show that the contribution of V_zz is the largest, with an average value of 32.74% of the total solution; the second and the third largest are V_zz and V_yy, with average values of 28.04% and 26.08%, respectively; the component V_xz contributes 11.81%. Validation with external data shows that each component has its characteristic value and that the information content of the component V_xz is not negligible and should be included for gravity field recovery. The orbit part as derived from high-low satellite-to-satellite tracking (SST-hl) to the GPS contributes mostly to the coefficients below degree and order (d/o) 20, and to non-zonal coefficients from d/o 20 to 80. The mean value of the contribution of the polar stabilization is the smallest with a value of 0.22%, nevertheless it is important. In addition to the contribution analysis in terms of the normal matrices, each individual component of the gradiometer has been combined with SST and polar stabilization, to give a set of single component gravity field models. These partially combined solutions are compared to the fully combined solution in terms of geoid differences. They show that the partially combined solution with V_zz is closest to the complete solution. Even closer is a combination with V_xx and V_yy. In addition to the GOCE-only solution, a GOCE-GRACE (Gravity Recovery And Climate Experiment) combined gravity field model is derived and the information content of GOCE and an available set of normal equations of GRACE are investigated. Results show that, as expected, GRACE dominates the solution below degree 90 and GOCE above degree 140.  相似文献   

Trace-element mobilization during Ca-metasomatism along a major fluid conduit: Eclogitization of blueschist as a consequence of fluid-rock interaction   总被引：5，自引：0，他引：5  

Andreas Beinlich  Reiner Klemd  Jun Gao 《Geochimica et cosmochimica acta》2010,74(6):1892-298

In the subduction complex of the Tianshan mountains, western China, massive blueschist is cross-cut by an eclogite-facies major fluid conduit surrounded by a reaction zone which is mainly composed of omphacite and garnet. Petrological as well as geochemical evidence suggest that formation of the vein and the eclogitic selvage around the vein was caused by fluid infiltration under peak metamorphic conditions of 21 ± 1.5 kbar and 510 ± 30 °C. The combination of whole-rock with mineral trace-element data as well as mass-balance calculations indicate that substantial differences exist between the unaltered host rock and the part of the system which was altered by fluid-rock interaction. These differences include: (1) depletion of mainly large-ion lithophile elements (LILE) and Li of up to 60% relative to their concentrations in the unaltered host rock; (2) an extreme enrichment of CaO (∼115%), Sr and Pb (>300%) in the altered parts of the vein-wall-rock system; (3) redistribution of heavy rare earth elements (HREE) from partly replaced rutile and recrystallized titanite in the blueschist-eclogite transition zone into newly grown garnet rims in the eclogitic selvage around the vein; (4) transformation of high Nb/Ta rutile into low Nb/Ta titanite which is associated with preferred mobilization of Nb over Ta; and (5) decoupling of Zr and Hf from Nb and Ta; the latter are depleted by ∼30% relative to the unaltered blueschist host rock whereas the former are depleted by only ∼10%. The prerequisite for the transformation of Ca-poor blueschist (6-7 wt.% CaO) into Ca-rich eclogite (up to 13 wt.% CaO) was the infiltration of a Ca-rich fluid. The release of trace elements can be attributed to partitioning of these elements into the passing fluid phase during dissolution-reprecipitation processes in the course of eclogitization. The reactivity of the precursor mineral assemblage and the chemical gradients between the reacting and passing fluid of the conduit are mainly responsible for trace-element mobilization in the studied samples. The suite of trace elements released upon fluid-induced eclogitization of the reactive wall-rock resembles that in island arc magmas showing strong enrichment of LIL elements, strong depletions in HFS elements and intermediate concentrations of REE.  相似文献   

Electron Exciter Speeds Associated with Interplanetary Type III Solar Radio Bursts     

M. J. Reiner  R. J. MacDowall 《Solar physics》2015,290(10):2975-3004

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Total waterborne carbon export and DOC composition from ten nested subarctic peatland catchments—importance of peatland cover,groundwater influence,and inter‐annual variability of precipitation patterns     

David Olefeldt  Nigel Roulet  Reiner Giesler  Andreas Persson 《水文研究》2013,27(16):2280-2294

Waterborne carbon (C) export from terrestrial ecosystems is a potentially important flux for the net catchment C balance and links the biogeochemical C cycling of terrestrial ecosystems to their downstream aquatic ecosystems. We have monitored hydrology and stream chemistry over 3 years in ten nested catchments (0.6–15.1 km²) with variable peatland cover (0%–22%) and groundwater influence in subarctic Sweden. Total waterborne C export, including dissolved and particulate organic carbon (DOC and POC) and dissolved inorganic carbon (DIC), ranged between 2.8 and 7.3 g m^–2 year^–1, representing ~10%–30% of catchment net ecosystem exchange of CO₂. Several characteristics of catchment waterborne C export were affected by interacting effects of peatland cover and groundwater influence, including magnitude and timing, partitioning into DOC, POC, and DIC and chemical composition of the exported DOC. Waterborne C export was greater during the wetter years, equivalent to an average change in export of ~2 g m^–2 year^–1 per 100 mm of precipitation. Wetter years led to a greater relative increase in DIC export than DOC export due to an inferred relative shift in dominance from shallow organic flow pathways to groundwater sources. Indices of DOC composition (SUVA₂₅₄ and a₂₅₀/a₃₆₅) indicated that DOC aromaticity and average molecular weight increased with catchment peatland cover and decreased with increased groundwater influence. Our results provide examples on how waterborne C export and DOC composition might be affected by climate change. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献