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Celestite formation, bacterial sulphate reduction and carbonate cementation of Eocene reefs and basinal sediments (Igualada, NE Spain) 总被引：5，自引：0，他引：5
Conxita Taberner James D. Marshall† James P. Hendry‡ Catherine Pierre§ & M. F. Thirlwall¶ 《Sedimentology》2002,49(1):171-190
Petrographic and geochemical studies of an Upper Eocene reef and associated basinal sediments from the mixed carbonate–siliciclastic fill of the south‐eastern Pyrenean foreland basin near Igualada (NE Spain) provide new insights into the evolution of subsurface hydrology during the restriction of a marine basin. The reef deposits are located on delta‐lobe sandstones and prodelta marls, which are overlain by hypersaline carbonates and Upper Eocene evaporites. Authigenic celestite (SrSO4) is an important component in the observed diagenetic sequences. Celestite is a significant palaeohydrological indicator because its low solubility constrains transportation of Sr2+ and SO42? in the same diagenetic fluid. Stable isotopic analyses of carbonates in the reef indicate that meteoric recharge was responsible for aragonite stabilization and calcite cementation. Sulphur and oxygen isotope geochemistry of the celestite demonstrates that it formed from residual sulphate after bacterial sulphate reduction, but also requires that there was a prior episode of sulphate recycling. Meteoric water reaching the reef and basinal areas was most probably charged with SO42? from the dissolution of younger Upper Eocene marine evaporites. This sulphate, combined with organic matter present in the sediments, fuelled bacterial sulphate reduction in the meteoric palaeoaquifer. Strontium for celestite precipitation was partly derived in situ from dissolution of aragonite corals in the reef and basinal counterparts. However, 87Sr/86Sr data also suggest that Sr2+ was partly derived from dissolution of overlying evaporites. Mixing of these two fluids promoted celestite formation. The carbonate stable isotopic data suggest that the local meteoric water was enriched in 18O compared with that responsible for stabilization of other reefs along the basin margin. Furthermore, meteoric recharge at Igualada post‐dated evaporite deposition in the basin, whereas other parts of the same reef complex were stabilized before evaporite formation. This discrepancy resulted from the spatial distribution of continental siliciclastic units that acted as groundwater conduits. 相似文献
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华南地区栖霞组菊花状天青石的交代及其地质意义 总被引：4，自引：0，他引：4
本文在收集大量菊花石标本的基础上，通过岩石薄片镜下鉴定及X射线衍射分析，识别了华南地区栖霞组菊花石假象内矿物的成因类型，建立了矿物交代序列，并通过对菊花石假象内各种矿物成分的电子探针分析和对交代方解石，脉方解石及其围岩的氧，碳同位素分析，探讨了菊花石交代过程中的成岩环境,合理地解释了菊花石内正延性玉髓和栖霞组内海泡石的成因。 相似文献
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Yan Jiaxin Zhao Laishi Faculty of Earth Sciences China University of Geosciences Wuhan Fang Nianqiao Department of Geology Mineral Resources China University of Geosciences Beijing 《中国地质大学学报(英文版)》1999,10(2):13
ＩＮＴＲＯＤＵＣＴＩＯＮＳｅｄｉｍｅｎｔａｔｉｏｎａｎｄｄｉａｇｅｎｅｓｉｓａｒｅｔｗｏｍａｊｏｒｆａｃｔｏｒｓｃｏｎ－ｔｒｉｂｕｔｉｎｇｔｏｇｅｏｃｈｅｍｉｃａｌｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｓｅｄｉｍｅｎｔａｒｙｃａｒｂｏｎ－ａｔｅｓ．Ｐｒｏ... 相似文献
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中国(天青石)锶矿床概述 总被引：8，自引：0，他引：8
中国 (天青石 )锶矿资源丰富 ,矿床以大型、特大型单一 (天青石 )锶矿为主 ,构成我国目前主要的工业锶源。依据成矿作用和成矿地质特征 ,将我国 (天青石 )锶矿床划分为沉积型、岩浆 热液型、沉积 热卤水改造型和表生淋积型等四大类七个亚类。主要产于印支、燕山、喜马拉雅三个旋回之中 ,不同类型矿床分别与一定的大地构造环境、沉积岩相、岩浆岩、热液及热卤水等作用有关。中国四川东南部、柴达木盆地东北部、苏南、鄂东南、云南云龙 -维西一带、陕西黄龙铺及四川攀西等 7个地区具有良好的找矿前景 相似文献
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The Lippmann diagram for the system(Ba, Sr)SO4-H2O was computed at 25 °Cby determining the solid-phase activity coefficientsfrom first principles calculations. Directcalculations of the mixing properties of thebarite-celestite series indicate this solid solutionbehaves as non-ideal and non-regular. At 25 °C,the enthalpy of mixing shows a minimum around 50 mole% SrSO4 due to an ordering tendency. Thefree energy of mixing shows two minima that delimit awide and symmetric miscibility gap (from 2.1 to 97.9 mole% SrSO4) at this temperature. The excessfree energy of mixing requires a Guggenheim expansionseries of 5 terms to be described, where the termswith odd exponents are null as a consequence of thesymmetric distribution of the mixing properties withcomposition. The Lippmann diagram shows a peritecticpoint that corresponds to the composition of an aqueoussolution which is simultaneously at equilibrium withthe two extremes of the miscibility gap. The largedifference between the solubility products of theendmembers involves a strong preferential partitioningof the less soluble endmember towards the solid phase,which explains the extremely Ba-poor composition ofthe aqueous solution (aqueous activity fraction forBa2+ = 0.000446 ) at the peritectic point. 相似文献
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A. Martínez-L. A. Uribe S. F. R. Carrillo P. J. Coreo A. J. C. Ortiz 《International Journal of Mineral Processing》2003,70(1-4):83-97
Flotation tests of synthetic mixtures of celestite (SrSO4) and calcite (CaCO3) minerals using sodium dodecyl sulfonate as collector were carried out using a factorial experimental design 23. The independent experimental variables included celestite grade in the feed (50% and 90% SrSO4), conditioning pH (6.5 and 9) and sodium silicate depressant concentration (10−5 and 10−3 M). All experiments were performed at a constant collector concentration (10−4 M) and conditioning time of 15 min. The response variables were recovery and grade of SrSO4 in the concentrate.The factors that had the greatest effect on the grade and recovery of celestite were the celestite grade in the feed (L) and the depressant concentration (C); also the combination of these factors significantly affected the response variables. The highest celestite yield (96% recovery, 98% grade) was obtained when a 90% of celestite grade in the feed was used. 相似文献
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青海大风山天青石矿床地质特征及成因分析 总被引：3，自引：0，他引：3
大风山天青石矿床位于柴达木盆地西北部,由Ⅰ、Ⅱ、Ⅲ、Ⅳ四个矿区组成,赋矿地层为第三系上新统狮子沟组,含矿层位不稳定,矿体多呈薄层状、扁豆状或透镜状产于含碳钙质泥岩中,矿石主要为天青石、菱Sr矿等;矿区内东西、北东东向次级断裂及舒缓短轴复式背斜构造严格控制着天青石矿体的产出形态;成矿物源具有多源性,一方面周边山系含Sr水为主要补给源,其次为富Sr的油田水。另外,深部含Sr卤水的补给也具有重要作用;矿床成因具有陆相湖泊化学沉积-热水沉积叠加改造型矿床特征。 相似文献
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The middle Permian Chihsia Formation of south China accumulated on a shallow shelf, and consists mainly of black to dark grey micritic limestone rich in chert nodules and organic matter. A unique type of nodular crystal cluster is distributed widely in the carbonate succession. Most crystal clusters consist of calcite. Some, however, are composed of celestite, and geochemical, microscopic and crystal morphological data suggest that celestite was the precursor of the calcite. The celestite developed displacively within the sediments during early diagenesis, before compaction and before local dolomitization of the host rock. Similar strontium isotopic values were obtained from the celestite clusters, replacement calcite, vein calcite and host rock. The values are within the range of middle Permian sea water. The strontium in the celestite was furnished chiefly by either diagenetic alteration of strontium‐rich marine aragonite to strontium‐poor calcite, or aragonite dissolution induced by aerobic oxidation of organic matter, or both. The sulphur isotopic values of the celestite are about 6–11‰ heavier than the sulphur isotopic value of sulphate in coeval sea water. Based on geological context, this difference is attributed to microbial reduction of porewater sulphate in the Chihsia sediments. 相似文献
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