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101.
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
102.
Abstract: Carbonate rocks of Cambrian (18 samples) and lower-middle Ordovician (11 samples) ages from South Korea were analyzed for sulfur contents of structurally substituted sulfate (SSS) and sulfides and their δ34 S values. The δ34 S values of SSS ranging from +25.9 to +45.2 permil, are averaged as +33.6 and +33.5 permil for the Cambrian and Ordovician rocks, respectively, which indicate high δ34 S values of the Cambro-Ordovician seawater. The SSS contents in the carbonate rocks are low being 2.9 to 17.3 ppm S (averaged as 7.0 ppm S). Sulfide sulfur, on the contrary, is much abundant containing 3 to 1,880 ppm S and the δ34 S values range widely between –17.6 and +31.1 permil. Sulfide sulfur of the studied rocks excluding impure carbonates has an average content of 187 ppm S and δ34 S value of +12.8 permil (n=24). The estimated δ34 S (sulfate–sulfide) values, which range from 13.8 to 25.4 permil in general with a few exceptions from 36.5 up to 52.3 permil for some impure carbonates, may provide evidence for the persistent oceanic anoxia with its temporary recovery during the Cambro-Ordovician time.
The SSS and sulfide sulfurs have often higher δ34 S values than the Mesozoic-Cenozoic ore sulfur (Ishihara et al., 2000). Since carbonate rocks are very reactive with circulating hydrothermal ore solution, high δ34 S values of the Korean ore deposits might be caused to some extent by 34 S enrichment from the host carbonates, resulting in the low SSS contents observed. 相似文献
The SSS and sulfide sulfurs have often higher δ
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地壳由半无限大的基岩上一层厚度为H^-的表土层组成,入射地震波为垂直的SH波,产生水平地面运动。当浅源大地震发生时,在极震区以外行波传播产生地面运动将使地壳介质有非线性的有限弹性变形。用小参数摄动法使非线性控制方程为线性化的小参数各阶控制方程,得出头两阶线性控制方程的解析解。 相似文献
105.
海洋平台结构振动的AMD主动控制参数优化分析 总被引:5,自引:0,他引:5
本文针对海洋平台结构的冰激振动和地震反应控制问题,提出了采用AMD主动控制的控制策略,结合JZ20-2MUQ平台结构进行了AMD控制系统的硬参数和软参数的优化分析,并就相应于最优参数下的AMD控制海洋平台结构冰激振动和地震反应的几种代表性工况进行了时程分析,得到了一些定性和定量的结论,为实际工程的控制设计提供了基础。本文提出的AMD主动控制方法对类似的海洋平台结构的控制问题也有参考价值。 相似文献
106.
2001年11月14日新疆-青海交界8.1级地震 总被引:3,自引:0,他引:3
简要介绍了2001年11月14日新疆-青海交界8.1级地震的预测情况,给出了中、美、日等对此次地震的震源参数测定和震源机制,以及余震的分布和加卸载响应比随时间的变化。进而对震区近期地震趋势进行预测。 相似文献
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108.
Shear wave statics using receiver functions 总被引:1,自引:0,他引:1
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110.