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651.
:本文讨论川甘青复理石盆地的地质概况、地壳属性、形成机制和资源前景。这个地区是中央造山带
中未发生陆陆碰撞的构造单元,包括甘南、青海东及川西北的倒三角形地区,过去称为“松潘甘孜造山带”。地壳波
速结构的特点包括:①上地壳分两层,上层的波速较低的沉积岩层,厚度可达7km,波速小于6.0km/s;下层为结晶
基底,波速6.0~6.2km/s。②中地壳为正常波速,但厚度较大,可达20km 以上。③下地壳波速从6.6km/s随深度
上升到7.3km/s,厚度亦增加到20km 以上。上述特点的产生与复理石盆地形成时洋壳的俯冲有关。构造演化可
分四个阶段,①洋壳俯冲阶段;②深水浊流沉积及等深流沉积阶段;③ 陆坡凸起沉积加剧阶段;④ 古特提斯洋封闭
以后,地壳推挤成高原阶段。川甘青复理石盆地也许是中国大陆浅层油气勘探的最后希望。在盆地边部及西秦岭
西延余脉,有良好的金矿资源开发前景。 相似文献
652.
Nickel enrichment in mantle olivine beneath a volcanic front 总被引:4,自引:1,他引:3
We found abnormally Ni-rich olivine (Fo = 93) with up to 5.3 wt% of NiO, ten times higher than the ordinary mantle value (0.4 wt%),
in a highly metasomatized mantle peridotite xenolith from Avacha volcano, the Kamchatka arc, Russia. The Ni enrichment displays
outward diffuse circular domains (<1 mm across) in fine-grained (mostly <100 μm) olivine-rich parts. Associated metasomatic
orthopyroxene also shows high NiO (<1.1 wt%). Such high Ni concentrations in olivine cannot be attained in ordinary residual
or cumulus peridotites, but are achievable via diffusion from Ni-rich sulfide melt. Sulfur-bearing silicic melt, the main
metasomatic agent for the Avacha peridotites, separated sulfide melt, which was fractionated to be Ni-rich at relatively low
temperatures. This is a new way of mobility and redistribution of Ni in the mantle, which is active in the mantle wedge, especially
beneath a volcanic front. 相似文献
653.
654.
陆相湖盆沉积有机质富集机理研究进展 总被引:6,自引:3,他引:3
有机质富集机理的研究对于寻找优质烃源岩、评价盆地的含油气远景具有重要的意义,尤其在日益受到人们重视的页岩气、致密气、油页岩等非常规资源的勘探开发影响下,其研究就显得愈来愈重要和紧迫。而有机质富集机理总体研究程度并不高,对于陆相湖盆有机质的研究相对更为薄弱。以陆相湖盆为研究对象,开展大量国内外关于有机质富集机理的调研,从有机质的生产、有机质分解与保存、有机质的稀释作用三个方面系统总结了陆相湖盆有机质富集的控制因素,并对湖泊与海洋有机质形成的差异性进行了对比分析。研究表明,湖盆有机质的生产受地区光照率、营养盐供给、湖盆地貌、气候环境、湖泊水介质条件、藻类季节性勃发、自养型细菌等的影响;有机质分解与保存受水体分层、细菌生物、无机矿物、水介质条件、黏土矿物、沉积速率等的影响;有机质的稀释作用受沉积速率的影响,并最终得出湖盆中有机质的含量实际上是“有机质生产-有机质分解-有机质稀释”三者相互作用的结果。提出今后值得进一步关注和亟待深入研究的两个方向:自养型细菌在何种环境条件下可以创造高有机质生产力以及不同的水介质条件对有机质分解与保存的影响。 相似文献
655.
L. T. Khemani Medha S. Naik G. A. Momin R. Kumar R. N. Chatterjee G. Singh Bh. V. Ramana Murty 《Journal of Atmospheric Chemistry》1985,2(3):273-285
The total suspended particulate (TSP) levels at Delhi (north India) were measured on 116 days between February and October 1980. The observations were stratified according to season and the values of cross-correlation of the TSP and its components were evaluated. High TSP (209 g m-3) levels were found during the summer period associated with hot and dry weather in the region and low TSP (109 g m-3) were found during the monsoon period. Most of the TSP mass was associated with natural soil elements, such as Fe, Al, Mn, Ca, and K. Only a fraction of the mass of the TSP was comprised of elements from anthropogenic sources, e.g., Pb, Ni, Cd, Sb, Cu, and Zn. The aerosols at Delhi were potentially basic in nature, unlike those in European countries which are acidic in nature and cause acid rainfall. 相似文献
656.
Samples of surface films and of the underlying bulk water at 0.2 m depth were taken in Lake Zürich on 48 occasions in 1986, 1988 and 1989, with the aim of assessing the appropriateness of applying existing neuston nomenclature to the organisms found in these films, of determining which organisms accumulate there during which periods of time, and of assessing the importance of the phytoplankton community in the development of neustonic biocoenoses. Lake Zürich surface films were found to support a community of high population density, consisting of organisms which had migrated from the benthal or pelagial, or which had entered the film via the atmosphere or inflowing rivers. In all samples, species originating from within the phytoplankton community accounted for the greatest proportion of the total abundance. Several of these species were found to exhibit a special preference for the surface biotope, viz. those with a relative frequency (rF) exceeding 10%, a mean enrichment factor (Ef) exceeding 100, and, in the majority of cases, with a greater concentration of individuals in the surface film than in the underlying bulk water layer. We suggest that only those organisms occurring in the surface films of large water bodies which fulfil the above criteria should be considered as belonging to the planktoneuston, in order to distinguish them from other species, the occurrence of which in surface films is merely coincidental. The fact that planktoneustonic algae are dominant in the surface films of Lake Zürich means that changes in the species composition of the planktonic algal biocoenosis directly affect the species composition of the neustonic algal biocoenosis. Thus, just as in the underlying bulk water, a succession can be observed in the algal biocoenosis of the surface films. However, because of the higher abundance of planktoneustonic algae there, this succession is distinct from that occurring in the pelagial. Factors bringing about these differences which are discussed for the case of the dominant planktoneustonic algae are: alterations in specific gravity; positive phototaxis; and enhancement of growth rates in surface films as compared with the underlying bulk water. 相似文献
657.
658.
喀拉通克Ⅰ号硫化铜镍矿床地球化学特征及矿化富集规律探讨 总被引:1,自引:0,他引:1
帕拉提·阿布都卡德尔 《新疆地质》1991,(4)
喀拉通克I号铜镍矿床是与基性杂岩体有关的岩浆硫化物矿床.矿床∑REE和稀土配分模式与国内同类矿床相似.铜、镍、钴等主要元素和金、银、铂等贵重金属元素赋存规律明显,与矿化富集规律计算机模拟结果吻合.岩石模式年龄等数项测试分析.为矿床的形成(物理化学条件分析)提供了较合理的依据. 相似文献
659.
河北东部太古代麻粒岩相深成片麻岩有两种类型:一种亏损放射性生热元素和大离子亲石元素;另一种富集这些元素。该文讨论了这种化学差异及造成差异的原因。 相似文献
660.