Biomarkers in sedimentary sulfides of precambrian age     

Bernd Mycke  Walter Michaelis  Egon T. Degens 《Organic Geochemistry》1988,13(4-6)

Samples of the Mt Isa formation (Australia, c, 1.5 Ga), and the Shungit formation (U.S.S.R., c. 2.3 Ga) were studied by organic geochemical means. All samples were freed of any low-molecular-weight solvent soluble organic material in order to insure the authenticity of the analysed material. The isolation of biochemical compounds entrapped in sulfides was the major goal of this work.Organic compounds that were entrapped during the early stages of sulfide formation may obviously survive extended periods of time and can be released by a mild hydrogenation of the sulfides. Preliminary investigations of the hydrocarbon fraction indicate n-alkanes, monomethylalkanes, cycloalkanes, and an unknown series of branched alkanes as major constituents. Their distribution patterns show great selectivity with respect to structures and chain lengths of individual compounds. Differences between the hydrogenation reaction product and the sample extract may arise from the release of a different kind of lipid material through dissolution of the sulfides.  相似文献   

Sulfur Content and Isotopic Ratio of Cambro-Ordovician Carbonate Rocks from South Korea: A Possible Source for Mesozoic Magmatic-hydrothermal Ore Sulfur     

Shunso ISHIHARA  Myung–Shik JIN  Yoshimichi KAJIWARA 《Resource Geology》2002,52(1):41-48

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 δ³⁴S values. The δ³⁴S 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 δ³⁴S 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 δ³⁴S 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 δ³⁴S value of +12.8 permil (n=24). The estimated δ³⁴S (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 δ³⁴S values than the Mesozoic-Cenozoic ore sulfur (Ishihara et al., 2000). Since carbonate rocks are very reactive with circulating hydrothermal ore solution, high δ³⁴S values of the Korean ore deposits might be caused to some extent by ³⁴S enrichment from the host carbonates, resulting in the low SSS contents observed.  相似文献   

中国第三次"资源环境经济论坛"研讨会综述   总被引：2，自引：0，他引：2  

成金华  汤尚颖 《地质科技情报》2002,21(4):111-114

中国第三次“资源环境经济论坛”研讨的问题包括排污权交易的市场化、新形势下的城乡关系、加入WTO和世界经济一体化进程中中国产业竞争力的培养、中国能源战略的选择、防灾减灾制度和大气环境的治理等。  相似文献   

断层旋性与地震危险性   总被引：1，自引：0，他引：1  

郭增建  吴瑾冰 《地学前缘》2001,8(2):247-252

文中以“平行同旋走滑断层减震”的观点论证了兰州、北京、昆明这些位于强震活动区的大城市今后百年内不会发生 6 .5级以上地震。以“平行异旋走滑断层加震”的观点解释了西南棱形块体北边界和南边界在发生大震方面相互促进的现象。对于由构造分段求震级来说 ,在遇到不同的横交断层作为分段点时 ,还需考虑将来发震时始破裂点的位置以及发震断层的旋性 ,不然就会造成对震级估计不足 ,继而成为抗震建设的潜在不安全因素。在主震后为了预报余震的强度 ,可应用物理学中的科里奥利力理论 ,应用时必须知道断层类型和旋性。对于走滑断层来说 ,左旋余震弱 ,右旋余震强。例如 1997年藏北玛尼 7.5级地震 ,余震仅为 5 .3级 ,震级偏小 ,因主震为左旋的缘故 ;1976年唐山 7.8级地震 ,余震可达 7.1级 ,因主震是右旋。对于逆断层来说 ,上盘错动方向在当地子午面左侧者余震强度大 ,在右侧者余震强度弱。据此讨论了 1999年台湾南投 7.6级大震余震强度达 7.1级是因为主震为逆断层 ,上盘向西错动。  相似文献   

长螺旋钻孔泵压灌注CFG桩缩径与对策   总被引：1，自引：0，他引：1  

贺为民  尚红  孙铭心  刘明军  常河林 《水文地质工程地质》2002,29(2):62-63,65

CFG桩是水泥粉煤灰碎石桩的简称。长螺旋钻孔泵压灌注CFG桩在层状土层的软硬分界处及软土中出现缩径，通过降低提钻速率和设置降水井点，缩径问题有所缓解，采取复打技术后彻底解决了缩径问题。  相似文献   

略论水资源系统的混合模型   总被引：1，自引：0，他引：1       下载免费PDF全文

郭元裕  沈佩君 《水科学进展》1993,4(2):147-152

大系统优化的关键在于模型的降维.混合模型可看作为一种降维方法,它通过把整个系统分解为联系比较松散的几个子系统,达到降维目的.从理论上对这类模型的建模原则、优化技术及其分类和特点进行了归纳和总结,说明了在多目标复杂水资源系统和排灌系统中这种混合模型的应用是十分有效的.  相似文献   

陕西略阳煎茶岭镍矿床成矿及矿石变质过程的地球化学研究     

Zhang Benren Chen Dexing Hu Yikeng 《地球科学》1986,(4)

矿床中存在着岩浆离熔成因的磁黄铁矿-镍黄铁矿矿石和热液改造成因的黄铁矿-针镍矿-辉镍矿矿石。研究证明现在矿石中存在的硫化物均为较低温度条件下的变质产物,并且矿物组合的更替不仅同温度变化有关,同时还受体系中氧逸度和硫离子活度的控制。矿物组合的地球化学分析表明,现有Fe-Ni-S体系低温（<300℃）相平衡图解之间存在着矛盾的原因可能是忽略了氧化-还原条件的影响。  相似文献   

Sulfides in petroleum     

J.D. Payzant  D.S. Montgomery  O.P. Strausz   《Organic Geochemistry》1986,9(6)

The homologous series of terpenoid sulfides previously reported to be present in Athabasca bitumen have been detected in a variety of petroleums from the Western Hemisphere. All 22 samples examined, ranging in age from Devonoan to Cretaceous, contained the terpenoid sulfides. A method is described for the isolation of sulfides from petroleums based on the selective oxidation of sulfides to more polar sulfoxides which are easily removed from the mixture and their subsequent reduction to sulfides. The sulfide content in the petroleum maltenes examined ranged from 0.3 to 16.1% w/w. In addition to the bicyclic and tetracyclic terpenoid sulfides a new series of tricyclic terpenoid sulfides has been identified, and the details of the isoprenoid side chain have been elucidated for all three homologous series. The distributions by carbon number of the bicyclic and tetracyclic homologous series of terpenoid sulfides show pronounced variations which are attributed to thermal maturity and degree of water washing of the petroleum, thus the ability to identify terpenoid sulfides should provide a useful tool for oil-oil and oil-source rock correlation studies. The bicyclic and tricyclic terpenoid sulfides have the same carbon framework as the carotenoids which suggest that these sulfides were accessory pigments in photosynthesis.  相似文献   

内蒙古白乃庙铜-金-钼矿床成矿机制——来自流体包裹体和He-Ar同位素的证据   总被引：1，自引：0，他引：1       下载免费PDF全文

周振华  车合伟  欧阳荷根  马星华 《地质学报》2017,91(3):542-560

白乃庙铜-金-钼矿是华北板块北缘中段一个重要矿床,其矿化特征既显示斑岩型蚀变特征,同时又表现出明显的后期造山作用改造的特点。本次研究通过系统的流体包裹体显微测温、激光拉曼和气液相色谱分析揭示其成矿流体为中—低温、中低盐度的CO_2(CO)-H_2O-CH_4(C_2H_2+C_2H_4)-NaCl-CaCl_2体系,流体混合作用和CO_2逃逸为成矿主要因素。富还原性流体的存在可能促使气相流体携带大量的Cu、Au等成矿元素迁移至较远点的白乃庙群地层,沿着片理或裂隙沉淀成矿。对不同成矿阶段矿石中黄铁矿的He-Ar同位素组成测试结果显示白乃庙矿床黄铁矿流体包裹体的~3He/~4He比值在0.06~0.71Ra之间,~(40)Ar/~(36)Ar比值为375.5~1436.3,指示成矿体系由不同性质和组成的两个端元流体混合而成,即混入了类似于MORB型地幔端元的高温高盐度流体和富含地壳放射成因氦但具有空气氩同位素组成特征的低温大气降水。白乃庙矿床属受后期造山作用改造的斑岩型铜-金-钼矿床,形成于古亚洲洋板块持续向南俯冲背景。  相似文献   

Insights into the extreme PGE enrichment of the W Horizon,Marathon Cu-Pd deposit,Coldwell Alkaline Complex,Canada: Platinum-group mineralogy,compositions and genetic implications     

《Ore Geology Reviews》2017

The W Horizon, Marathon Cu-Pd deposit in the Mesoproterozoic Midcontinent rift is one of the highest grade PGE repositories in magmatic ore deposits world-wide. The textural relationships and compositions of diverse platinum-group mineral (PGM) and sulfide assemblages in the extremely enriched ores (>100 ppm Pd-Pt-Au over 2 m) of the W Horizon have been investigated in mineral concentrates with ∼10,000 PGM grains and in situ using scanning electron microprobe and microprobe analyses.Here we show, from ore samples with concentrations up to 23.1 Pd ppm, 8.9 Pt ppm, 1.4 Au ppm and 0.73 Rh ppm, the diversity of minerals (n = 52) including several significant unknown minerals and three new mineral species marathonite (Pd₂₅Ge₉; McDonald et al., 2016), palladogermanide (Pd₂Ge; IMA 2016-086, McDonald et al., 2017), kravtsovite (PdAg₂S, IMA No 2016-092, Vymazalová et al., 2017). The PGM are distributed as PG-, sulfides (52 vol%), -arsenides (34 vol%), -intermetallics of Au-Ag-Pd-Cu and Pd-Ge(10 vol%) and -bismuthides and tellurides (4 vol%). The discovery of abundant (>330 grains) large unknown sulfide minerals with Rh allows us to present analyses three significant potentially new minerals (WUK-1, WUK-2, WUK-3) that are all clearly enriched in Rh (averaging 4.2, 8.5 and 28.21 wt% Rh respectively). Several examples of paragenetic sequences and mineral chemical changes for enrichment of Cu, Pd and Rh with time are revealed in the PGM and base-metal sulfides. We suggest this enhanced metal enrichment formed in response to increasing fO₂ causing the oxidation of Fe²⁺ to Fe³⁺ and to a lesser extent, S.Phase relations in the Ag-Pd-S, Rh-Ni-Fe-S, Pd-Ge, Au-Pd-Cu-Ag, Pd-Ag-Te systems help constrain the crystallization temperatures of the majority of ore minerals in the W Horizon at ∼500 °C or moderate to high subsolidus temperatures (400–600 °C). Local transport by aqueous fluids becomes evident as minerals recrystallize down to <300 °C. The PGE-enriched W Horizon ores exhibit a complex post-magmatic history dominated by the effects of oxidation during cooling of a Cu-PGE enriched magma source from a deep reservoir.  相似文献