Barium in Deccan Basalt Rivers: Its Abundance, Relative Mobility and Flux     

Anirban Das  S. Krishnaswami 《Aquatic Geochemistry》2006,12(3):221-238

The concentration of dissolved Ba in a number of rivers having their drainage almost entirely in Deccan Trap basalts has been measured. These results along with available data on the abundances of major elements in these waters, and on Ba and major elements in bed sediments of these rivers provide a measure of (i) the relative mobility of Ba during chemical weathering and erosion of basalts, particularly with respect to alkaline earths, Mg, Ca and Sr, and (ii) the flux of Ba out of the Deccan and its global significance. The concentration of dissolved Ba ranges from 8 to 105 nM. The average Ba/Mg*, Ba/Ca* and Ba/Sr (* is concentration corrected for atmospheric contribution) in waters is lower than the corresponding mean ratios in Deccan basalts, though they overlap within errors. Majority of the water samples, however, have ratios less than that in basalts. These findings can be interpreted as a cumulative effect of limited release/mobility of Ba during chemical weathering and erosion of basalts and its reactive behaviour in waters which promote its association with clays and oxy-hydroxides of Fe. These results also indicate that during chemical erosion of Deccan basalts, Ba is the least mobile among the alkaline earth elements. The abundance of Ba in sediments and their Ba/Al ratios relative to basalts are consistent with the above conclusion. Ba/Mg and Ba/Ca ratios in water and in sediments from the same location are strongly correlated; however, the mean ratios in waters are far less than those in sediments. This is a result of limited Ba mobility, effectively 5–6 times lower than that of Mg. The annual flux of dissolved Ba out of the Deccan Traps is ~1 × 10⁷ moles, ~ 0.2% of its global riverine transport to oceans. The contribution of dissolved Ba from Deccan Traps, seem lower than its aerial coverage, ~ 0.5% of the global drainage area; the potential causes for this could be the lower abundance of Ba in basalts relative to “average continental crust”, and its behaviour during chemical weathering and erosion.  相似文献   

南海表层沉积物中生物钡的分布特征及其与初级生产力的关系   总被引：3，自引：0，他引：3  

倪建宇  潘建明  扈传昱  刘小涯 《地球化学》2006,35(6):615-622

分析了南海东部53个站位表层沉积物中生物钡、铝以及有机碳和生物硅等生源物质的分布特征。结果表明,南海东部表层沉积物中的有机碳含量在研究区的北部陆架区出现高值,而在吕宋岛以西的深海则最低;生物硅的平面分布则表现为在吕宋岛以西的深海低沉积速率区出现高值,而低值则出现在高沉积速率的北部海域;生物钡的平面分布与生物硅的分布特征相似,高值出现在吕宋岛以西的深海区,且表现出自北而南沉积物中生物钡的含量逐渐增加的趋势。研究区内初级生产力表现为从北向南增加的趋势,而沉积物中生物钡的含量也呈现相似的趋势,表明沉积物中生物钡的含量和上层水体的生产力有一定的相关性。但表层沉积物中生物钡与有机碳呈弱的负相关关系,而与生物硅显著相关,且生物钡和生物硅与水深的相关性均呈现显著的相关性。因此,在采用沉积物中生物钡含量研究南海上层水体初级生产力时应谨慎对待。  相似文献   

Generation and accumulation of Quaternary shallow gas in eastern Qaidam Basin, NW China     

苏爱国赵文智  党玉琪张水昌黎茂稳  庞雄奇周瑞年管自强  徐子远张道伟谭彦虎  陈践发李素梅 《中国地球化学学报》2006,25(1):43-55

1INTRODUCTION SHALLOW(MOSTLYBIOGENIC)GASACCOUNTSFOROVER20%OFTHEWORLD’SDISCOVEREDGASRESERVES(RICEAND CLAYPOOL,1981;CLAYPOOLANDKAPLAN,1974),AND REPRESENTSONEOFTHEUNCONVENTIONALENERGYSOURCES THATINCREASINGLYATTRACTTHEATTENTIONOFPETROLEUMGEOL OGISTS.NUMEROUS…  相似文献   

柴达木盆地东部微体化石丰度与天然气源岩   总被引：1，自引：0，他引：1  

门相勇孙镇城  曹丽张海泉  乔子真孙乃达 《地质论评》2006,52(3):363-369

柴达木盆地东部三湖坳陷上新统第四系自生自储的天然气藏，已成为我国四大天然气产区之一。与柴达木盆地侏罗系、古近系一新近系原油伴生气与凝析气不一样，三湖坳陷生物成因气的气源岩母质主要是浅水湖泊动植物的有机质。在该区诸多门类的生物群落中，具有双壳易于保存为化石的微体动物介形类的丰度，与生物成因气源岩的分布密切相关，介形类化石丰度高低变化基本上反映了气源岩的好坏或有无。本文以三湖坳陷介形类化石丰度纵横向变化，提出了三湖坳陷进一步勘探天然气的方向：向坳陷北、东和南部比向西部红三旱四号方向较有利，因为该坳陷西部湖水含盐量太高，介形类等水生生物能生存者不多，生烃母质量少。  相似文献   

等离子体发射光谱法测定重晶石中钡铁和硅   总被引：3，自引：0，他引：3  

杨德君  陈利平 《岩矿测试》1998,17(4):317-318

重晶石经Ｎａ２ＣＯ３熔融,水浸取,过滤。沉淀经ＨＣｌ溶解后,用电感耦合等离子体发射光谱法同时测定主成分ＢａＳＯ４和次量成分Ｆｅ２Ｏ３以及滤液中的ＳｉＯ２,结果与部颁标准方法符合。方法精密度好,主量组分ＢａＳＯ４测定的ＲＳＤ（ｎ＝６）为０．２４％,次量组分Ｆｅ２Ｏ３和ＳｉＯ２的ＲＳＤ（ｎ＝６）分别是３．６９％和１．４５％。  相似文献   

Magnetofossils in the sediment of Lake Baikal, Siberia   总被引：1，自引：0，他引：1  

J.A. Peck  J.W. King 《Earth and Planetary Science Letters》1996,140(1-4):159-172

A multidisciplinary approach involving rock-magnetics, transmission electron microscopy, and X-ray diffraction was used to identify a biogenic magnetite component in the Lake Baikal, Siberia, sedimentary magnetic record. The distinctive biogenic component to the magnetic record occurs as chains of single-domain, elongate hexagonal and tear-drop cone-shaped magnetite particles. These magnetofossils are inferred to be magnetosomes produced by magnetotactic bacteria living in the surficial sediment throughout Lake Baikal. Postdepositional reduction diagenesis results in the loss of the fine-grained magnetofossils at depth. In addition, this study shows that the fine-grained magnetofossils are removed by the process of storage diagenesis during long periods (21 months) of core storage, which results in a change to a coarser grained, slightly higher coercivity bulk magnetic mineral assemblage. Although the Lake Baikal sedimentary magnetic record has several distinct and complex components, by determining their origin this study has shown that the sediments are well suited for environmental magnetic study.  相似文献   

沉积铁矿形成过程中的生物作用   总被引：3，自引：0，他引：3  

陈志明 《地球科学进展》1992,7(6):56-59

    沉积赤铁矿和层控黄铁矿、菱铁矿的成矿过程中都离不开生物的作用。不同情况下，其表现形式不尽相同。生物的活动形成赤铁矿受层石、毒球状黄铁矿以及有机质的还原作用由赤铁矿转变为菱铁矿。
    冀西北宣龙地区铁质叠层石和铁质核形石同心纹层中普遍含有微体古植物化石，属于低等蓝藻类，形态以丝状体为主，部分为羽状体，它们直接地参与了铁的成矿作用。
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硅钙钡镁合金中钡钙镁的测定   总被引：5，自引：0，他引：5  

沙艳梅赵学沛  王明军何雪梅 《岩矿测试》2004,23(4):308-310

采用HNO3-HF-HClO4分解试样，分别以硫酸钡重量法、EDTA容量法及原子吸收法测定了硅钙钡镁合金中的Ba、Ca、Mg，结果与硅钙钡合金标样的标准值相符。加标回收试验的回收率为99．00％～102．00％，样品5次测定的RSD小于1．19％。  相似文献   

非常规含气系统的研究和勘探进展   总被引：14，自引：2，他引：14  

陈建渝  唐大卿  杨楚鹏 《地质科技情报》2003,22(4):55-59

从含油气系统的观点出发，分别总结了煤层气、盆地中心气、裂缝型页岩气、浅层生物气和天然气水合物五类非常规含气系统的地质和地球化学特征，修改和补充了传统油气系统的概念，为天然气新领域的开拓和发展提供了新的思路。常规天然气藏为浮力驱动的存在于构造或地层圈闭中的独立气藏，而非常规天然气藏一般不是浮力驱动的聚集气藏，它们在区域上呈连续弥散的聚集，常常与构造和地层圈闭无关，因此，它们的成藏要素和过程与常规天然气藏有所区别。在煤层气和页岩气中，烃源岩既是储层，又是盖层且运移距离很短；储层多为低孔隙度、低渗透性的裂缝型储层，主要为毛细管力和水力封闭，大型煤层气藏可以出现在向斜构造中。  相似文献   

Fluid seepage along the San Clemente Fault scarp: basin-wide impact on barium cycling     

Marta E. Torres  James McManus  Chih-An Huh 《Earth and Planetary Science Letters》2002,203(1):181-194

Material fluxes associated with fluid expulsion at cold seeps and their contribution to oceanographic budgets have not been accurately constrained. Here we present evidence that the barium released at cold seeps along the San Clemente Fault zone may significantly impact the geochemical budget of barium within the basin. Barium fluxes at seep localities on the fault scarp, measured with benthic chambers, reach values as high as 5 mmol m⁻² day⁻¹. This is the largest dissolved barium flux measured to date at a cold seep. The discharge of barium-rich fluids results in formation of massive barite deposits along the escarpment wall. The deposits are young (approximately 8 yr) and appear to grow at a minimum rate of 0.2 cm yr⁻¹. This rapid growth rate requires a barium efflux rate that is about two orders of magnitude higher than the measured dissolved flux. We believe that the discrepancy reflects a highly localized seepage system and that chambers positioned as close as possible to the growing chimneys did not sample the foci of fluid discharge. Transport of fine barite particles from the seeps may be responsible for excess rates of barium accumulation throughout the San Clemente Basin, relative to other basins in the California Margin. Based on a preliminary budget, we estimate that cold-seep barite is accumulating at the basin floor in San Clemente at a rate of 2 μmol m⁻² day⁻¹, a value that is comparable to the total barium accumulation rates driven by detrital and biogenic components in neighboring basins. Remobilization of cold-seep barite on the basin floor adds to that driven by the biogenic barium flux and results in benthic barium recycling rates (effluxes) within the San Clemente Basin that are as much as seven times higher than the effluxes from surrounding borderland basins. Our estimates imply that processes associated with fluid seepage along the San Clemente Fault significantly contribute to the basin’s barium cycle. The strontium isotopic composition of the seep barite is significantly different from marine ‘biogenic’ barite, which is known to accurately record seawater composition. In addition, the seep deposits are depleted in ²²⁶Ra relative to their modern biogenic counterparts, and are likely to be a source of radium-depleted particulate barium to the basin. Thus the impact of barite transport from seeps on the San Clemente escarpment to the basin floor might also have implications for the geochemistry of elements other than barium.  相似文献