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131.
青藏高原南羌塘基性岩墙群U-Pb和Sm-Nd同位素定年及构造意义 总被引:17,自引:0,他引:17
羌塘地区是青藏高原古特提斯研究的关键地区,羌塘南部地区基性岩墙群的侵位时代与构造背景对确定古特提斯阶段联合古陆解体的具体时间和青藏高原构造演化有重要意义。选择单颗粒锆石U-Pb法和全岩Sm-Nd等时线法对基性岩墙进行定年研究,获得了(312±4)Ma单颗锆石U—Pb谐合线年龄和(299±13)Ma和(314±5)Ma两个Sm-Nd全岩等时年龄。结合区域地质资料研究认为,基性岩墙群为羌塘地块裂离作用的产物,所获得的同位素年龄代表了基性岩墙群的侵位时间,为羌塘地块裂解提供了构造事件年龄,为重塑龙木错—双湖古特提斯洋盆的形成演化过程提供了重要信息。 相似文献
132.
133.
大别山南部宿松磷矿含磷地层的时代归属与变形特征及其构造评价 总被引:1,自引:0,他引:1
根据对大别山南部宿松磷矿含磷地层的区域分布、地层序列、时代归属、构造变形的系统研究,提出磷矿层属震旦系的新认识。含磷岩系经受了两次强烈的变形改造,原始层理经过了强烈改造,宿松磷矿构成总体包络面呈北西西走向、向南倾斜的褶皱化单斜。矿层的多层化、尖灭复合和加厚现象等主要受构造的控制,而非完全受古地形的控制。用褶皱的观点对原先勘探剖面中的磷矿体进行了重新圈连,籍以指导磷矿的调查、评价和开采。最后对磷矿分布的古地理特征进行了讨论,并从构造的观点对磷矿进行了评价。 相似文献
134.
对吉林南部地区煤矿主采煤层中的As、B、Ba、Cd、Cu、Hg、Pb、Se、Sr等微量元素的分析结果表明,太原组与山西组由于成煤环境不同,微量元素组成及含量存在一定的差异:太原组原煤中As、B、Hg、Pb、Se、Zn的含量明显高于山西组,山西组原煤中Ba、Cr、Cu、Mn、V的含量明显高于太原组。吉南煤区原煤中As、B、Hg、Pb、Se明显高于地壳元素平均值,呈富集状态,Co、Cd与地壳平均值接近,其他元素均亏损。与全国煤中微量元素相比,该区原煤中As、Ba、Co、Cr、Cu、Hg、Ni、Pb、Se、V、Zn的含量高于全国平均值,B、Mn、Sr含量低于全国平均值。微量元素赋存状态及相关分析表明,Fe与亲硫有害元素As、Cu、Hg、Pb、Se具有显著相关关系,说明煤中黄铁矿及其他硫化物是许多有害微量元素的重要载体。 相似文献
135.
The main purpose of this study is to model the δ13C values of methane derived from coal by combining kinetic-simulating experiment with the gas chromatography-isotope ratio mass spectrum (GC-IRMS) analysis. The stable carbon isotopic variation of methane in pyrolysates with heating temperature indicates that the assumptions for both a constant kinetic isotope effect (α) and a uniform initial isotopic composition (δ13Co) are impractical for explaining the carbon isotopic fractionation during coalification. For purposes of simplification, two approaches are used in this paper to deal with the heterogeneity of terrestrial organic matter. One is that, assuming a uniform initial isotopic composition (i.e., δ13Ci, o=δ13Co) for all methane-generating precursors in coal, the isotopic variation of methane is fitted by adjusting ΔEa, i (Ea13C, i−Ea12C, i) for each hypothetical reaction. The other is that, assuming a constant kinetic isotope effect during the whole gas formation, that is all ΔEa, i values are identical, the modeling of methane isotopic composition is achieved by changing the 13CH4 generation potential of each reaction (fi, 13C), namely, by adjusting the initial δ13C value (δ13Ci, o) for each methane-generating precursor. Results of the kinetic calculation shows that the two simulating methods can yield a similar result at a geological heating rate of 2 °C/My, which further demonstrates that those natural gases with methane δ13C value being approximately −36‰ are possibly sourced from the upper Triassic coal measure strata in the Northwestern Sichuan Basin. 相似文献
136.
Charnockitic magmatism in southern India 总被引:2,自引:0,他引:2
Large charnockite massifs cover a substantial portion of the southern Indian granulite terrain. The older (late Archaean to
early Proterozoic) charnockites occur in the northern part and the younger (late Proterozoic) charnockites occur in the southern
part of this high-grade terrain. Among these, the older Biligirirangan hill, Shevroy hill and Nilgiri hill massifs are intermediate
charnockites, with Pallavaram massif consisting dominantly of felsic charnockites. The charnockite massifs from northern Kerala
and Cardamom hill show spatial association of intermediate and felsic charnockites, with the youngest Nagercoil massif consisting
of felsic charnockites. Their igneous parentage is evident from a combination of features including field relations, mineralogy,
petrography, thermobarometry, as well as distinct chemical features. The southern Indian charnockite massifs show similarity
with high-Ba-Sr granitoids, with the tonalitic intermediate charnockites showing similarity with high-Ba-Sr granitoids with
low K2O/Na2O ratios, and the felsic charnockites showing similarity with high-Ba-Sr granitoids with high K2O/Na2O ratios. A two-stage model is suggested for the formation of these charnockites. During the first stage there was a period
of basalt underplating, with the ponding of alkaline mafic magmas. Partial melting of this mafic lower crust formed the charnockitic
magmas. Here emplacement of basalt with low water content would lead to dehydration melting of the lower crust forming intermediate
charnockites. Conversely, emplacement of hydrous basalt would result in melting at higher {ie565-01} favoring production of
more siliceous felsic charnockites. This model is correlated with two crustal thickening phases in southern India, one related
to the accretion of the older crustal blocks on to the Archaean craton to the north and the other probably related to the
collision between crustal fragments of East and West Gondwana in a supercontinent framework. 相似文献
137.
138.
四川盆地潜在震源区的细致划分 总被引:2,自引:0,他引:2
四川盆地包括川中台拱和川东陷褶束的范围,具有相对稳定的大地构造环境.鉴于该地区地震活动水平相对较低、发震构造不甚明确的特点,在编制1990年版中国地震烈度区划图时,划分的潜在震源区面积也相对较大.本文在总结四川盆地中强地震(Ms=4.7-5.7)发震构造条件的基础上,用地震构造类比原则对四川盆地的潜在震源区进行了重新划分.确定潜在震源区边界时,充分考虑了背斜轴走向、背斜构造的影响带宽度、小震活动密集条带和余震的分布范围.得到了四川盆地更加细致的潜在震源区划分方案.这对于低地震活动水平地区的潜在震源区的细化研究具有一定参考意义。 相似文献
139.
Curie-point depth from spectral analysis of magnetic data in central-southern Europe 总被引:3,自引:0,他引:3
The basal depth of the outer layer with internal magnetic sources was calculated from magnetic data available within a roughly 500 km wide and 1200 km long area, running from central Germany to southern Italy. The dataset, deriving from different aeromagnetic surveys, is reduced to the reference altitude of 3000 m a.s.l. and a reference year of 1980.0. The adopted method, which transforms the spatial data into the frequency domain, provides a relationship between the two-dimensional spectrum of the magnetic anomalies and the top and centroid depths of the magnetic sources. The magnetic layer bottom depth (MLBD) thus obtained is 29-33 km deep in the stable areas (central Europe Variscan units, Corsica-Sardinia Variscan block) and corresponds to the Moho, having an average temperature of 560 °C. From the Alps to the Apennines, MLBD ranges between 22 and 28 km and is clearly shallower than the Moho. In these units, the wide variation of MLBD appears to be compatible with the presence of shallow magnetised bodies, consisting of lower crustal rocks (Ivrea-Verbano zone), ophiolitic units (Penninic zone and Voltri Massif) and intrasedimentary basic volcanic bodies (Po Basin). An average value of 25 km can be attributed to MLBD, which corresponds to a temperature of 550 °C. In the peri-Tyrrhenian zone and the Ligurian Sea, MLBD is below the Moho, which ranges from 17 to 20 km depth, and it has a temperature matching approximately to the Curie temperature of magnetite (580 °C). 相似文献
140.
ZHU Guangyou ZHANG Shuichang LIANG Yingbo DAI Jinxing & LI Jian Research Institute of Petroleum Exploration Development PetroChina Beijing China 《中国科学D辑(英文版)》2005,48(11)
Isotopic evidence of TSR origin for natural gas bearing high H2S contents 1961 As the hazardous component of natural gas, the ex-istence of H2S, due to its extremely strong toxicity and corrosivity, not only decreases the percentage of hy-drocarbon gas within natural gas and reduces its in-dustrial value, it also threatens each aspect of drilling and exploitation. It frequently causes serious safety accidents[1] and leads to the E&P cost and risk of natural gas with higher H2S contents be… 相似文献