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51.
52.
Wang Yunliang Li Juchu Han Wenxi Wang Wangzhang Chengdu College of Geology Chengdu Sichuan Jiang Minxi 《《地质学报》英文版》1993,67(3)
This paper discusses the discrimination principles. deduction and methods for probing into the source composition of mantle-derived magma. The magmatophile (incompatible) source elements are not all optimal tracers for mantle source composition. The ratios of two strong magmatophile elements (D<1) or the ratios of two trace elements with the same D value are not controlled by the formation mode and evolution degree of a magma, but maintain the characteristics of their composition in mantle source region prior to the magma formation. The ratios are related to different mantle-crust structures and dynamics. The mantle source composition of the Emeishan Basalt series is similar to that of the South Atlantic Rio Grande Rise-Walvis Ridge Basalts and Brazil continental-margin basalts. This may indicate that these basalt series might have similar source regions and tectonic environments. 相似文献
53.
Geochemical research on C—O and Sr—Nd isotopes of mantle-derived rocks from Shandong Province,China 总被引:1,自引:0,他引:1
This paper presents systematic studies on the C—O and Sr—Nd isotopic compositions for Cretaceous Badou carbonatites, Fangcheng
basalts, and Jiaodong lamprophyres and Paleozoic Mengyin kimberlites in Shandong Province, China. Paleozoic kimberlites have
normal and uniform C—O isotopic compositions with δ13C and δ18O in the range of −4.8‰—−7.6‰ and +9.9‰—+13.2‰, respectively. However, Cretaceous three different types of mantlederived rocks
have quite different C—O isotopic compositions, indicating that the mantle sources are probably partially contaminated with
organic carbon-bearing crustal materials. These Cretaceous rocks show uniform and EMII-like Sr—Nd isotopic compositions and
also indicate that the mantle sources were affected by recycled crustal materials. Comparative studies of C—O and Sr—Nd isotopes
reveal that the lithospheric mantle beneath the eastern North China Craton had different isotope characteristics in the Paleozoic,
the early Cretaceous, and the Tertiary time. This demonstrates that the lithospheric mantle beneath the region underwent at
least twice reconstructions since the Paleozoic. Available data imply that the first reconstruction mainly happened during
the Triassic-Jurassic time with gradual changes and the second in the Cretaceous with abrupt changes. Results also show that
the early Cretaceous (especially at 120-130 Ma) was perhaps the key period leading to the dramatic change of the Mesozoic
geodynamics on the eastern North China Craton. 相似文献
54.
四川大渡河金矿田位于扬子地台西缘金成矿带北段,受大渡河剪切带控制。本文以该矿田黄金坪、白金台子、黑金台子金矿为例,根据对黄铁矿流体包裹体氦氩同位素、黄铁矿硫同位素以及与黄铁矿共生的石英流体包裹体的氢氧同位素组成测定,讨论了大渡河金矿田成矿流体的来源。结果显示,该金矿田黄铁矿流体包裹体中的~3He/~4He变化较小,为0.16~0.86Ra,而~(40)Ar/~(36)Ar的变化较大,为298~3288;而黄铁矿δ~(34)S同位素变化范围较窄,一般为0.7‰~4.2‰,集中于2.5‰~3‰,显示硫地幔来源的特点;石英流体包裹体的氢、氧同位素分别为-2.6‰~ 3.64‰和-39.13‰~-108.23‰,说明成矿流体为岩浆水和大气降水的混合流体。本文认为大渡河金矿田成矿流体是地幔流体与地壳流体的混合作用的结果,而以地壳流体占主导地位。其中,地幔流体为与下伏隐伏岩体有关的岩浆水,而地壳流体端元则是含有一定放射成因Ar的大气降水,并且温度小于200℃。 相似文献
55.
从赣中马鞍坪地区采集了 11个水样分析了温泉及冷泉的氢、氧同位素组成 ,得出温泉水起源于大气降水补给。在此基础上 ,对 4个温泉采集了气样 ,测定了气体组成的含量和氦同位素组成 ,以及二氧化碳的碳同位素 ,结果表明 :马鞍坪地区地热气体为二氧化碳型 ,温泉气的二氧化碳含量很高 ,占总体积的 97%以上 ,二氧化碳气体的δ1 3C值变化于 -4 18‰~ -7 0‰ ,平均为 -5 .63‰ ,为变质无机成因和幔源无机成因的混合物 ;其3He/4He比值变化于 (1.72± 0 .15 )×10 7~ (2 .5 5± 0 .19)× 10 - 7之间 ,R/Ra值均小于 1,属壳源成因 相似文献
56.
河北平原地下水氦氩同位素特征 总被引:1,自引:1,他引:1
通过对河北平原地下水氦同位素进行分析比较,根据过剩He(4He exc)、3He/4He比值、δ3He和36Ar/38Ar及40Ar/36Ar值分析认为,河北平源地下水氦氩同位素有7个特征;①地下水中过剩He浓度沿地下水的流向而增高;②地下水中过剩He浓度随着地下水埋深加大而增高;③满城-沧州剖面上过剩He浓度大于石家庄-衡水剖面上的过剩He浓度;④河北平原地下水主要是由大气隆重水补给的;⑤衡水热水过剩He浓度很高(>674.83×10-8cm3STPg-1水);⑥地下水的36Ar/38Ar比值平均值为5.37,非常接近地球大气的比值(5.35);⑦地下水的40Ar/36Ar比值从296-412,均比大气氩的40Ar/36Ar比值(295.6)大,这表明40Ar都是放射成因的,且具有“年代积累效应”。 相似文献
57.
Radon Precursory Signals for Some Earthquakes of Magnitude > 5 Occurred in N-W Himalaya: An Overview
Vivek Walia Hardev Singh Virk Bikramjit Singh Bajwa 《Pure and Applied Geophysics》2006,163(4):711-721
The N-W Himalaya was rocked by a few major and many minor earthquakes. Two major earthquakes in Garhwal Himalaya: Uttarkashi
earthquake of magnitude Ms= 7.0 (mb = 6.6) on October 20, 1991 in Bhagirthi valley and Chamoli earthquake of Ms= 6.5 (mb = 6.8) on March 29, 1999 in the Alaknanda valley and one in Himachal Himalaya: Chamba earthquake of magnitude 5.1 on March
24, 1995 in Chamba region, were recorded during the last decade and correlated with radon anomalies. The helium anomaly for
Chamoli earthquake was also recorded and the Helium/Radon ratio model was tested on it. The precursory nature of radon and
helium anomalies is a strong indicator in favor of geochemical precursors for earthquake prediction and a preliminary test
for the Helium/Radon ratio model. 相似文献
58.
D.W. Graham L.M. Larsen B.B. Hanan M. Storey A.K. Pedersen J.E. Lupton 《Earth and Planetary Science Letters》1998,160(3-4):241-255
Picrites from the 61 million year old Vaigat Formation of the Nuussuaq Peninsula in West Greenland have 3He/4He ratios trapped in olivine phenocrysts which range up to 30 times the atmospheric ratio. These high values, measured during gas extraction by crushing in vacuum, are similar to the highest magmatic 3He/4He ratios found in young terrestrial volcanic rocks. By analogy with young basalts, in which crushing selectively extracts magmatic helium, any significant cosmogenic 3He appears to be absent in these picrites. Additional evidence for the absence of cosmogenic helium is provided by fusion results on the crushed olivine powders and by a single stepwise crushing experiment, in which only magmatic and radiogenic helium components are resolvable. The West Greenland picrites have Pb, Nd and Sr isotope compositions which overlap those found in picrites from Iceland and in basalts from Loihi Seamount, localities which today also have high 3He/4He ratios. Isotopic variations in He, Pb, Nd and Sr for the West Greenland picrites are interpreted to largely result from interaction of the early Iceland mantle plume with the upper mantle during plume ascent and dispersion beneath the continental lithosphere. The presence of high 3He/4He ratios in West Greenland, and the onset of magmatism across the North Atlantic Volcanic Province near 62 Ma, supports the hypothesis for very rapid dispersion (>1 m/year) of mantle plume head material during the earliest stages of plume impact, as predicted in recent numerical simulations of plume behavior during thermal mantle convection with non-Newtonian rheology. 相似文献
59.
天然气中氦同位素分布及构造环境 总被引:16,自引:1,他引:16
通过采集天然气样334个,测量了它们的氦同位素组成。3He/4He值分布在056×10-8~721×10-6范围。3He/4He值分布与天然气储层时代无明显的相关性,而在空间展布上有较明显的规律。东部含油气区3He/4He值主要分布于10-7~10-6范围,西部含油气区在10-7~10-8的范围,中部地区分布在056×10-9~056×10-8范围,3He/4He值的分布与我国构造环境大的格局有很好的相关性。3He/4He的高值区构造环境活动性强,低值区具有最稳定的大地构造属性,西部地区3He/4He值介于东部和中部,具有次稳定的构造环境。 相似文献
60.
山东蓝宝石原生矿床成因探讨 总被引:17,自引:0,他引:17
山东昌乐地区广泛分布晚第三纪碱性玄武岩。该时代的玄武岩浆喷出活动在构造上受到大陆裂谷型沂沐断裂带的控制。玄武岩浆活动是喷溢型而不是喷发型。富含蓝宝石的寄主玄武岩比不含蓝宝石的玄武岩含Na2O+K2O、Al2O3和TiO2高,而含SiO2低,其成分投影点落入(K2O+Na2O)-SiO2图中的碱性玄武岩区。含蓝宝石的玄武岩中含有大量的二辉橄榄岩,该种岩石是上地幔部分熔融出玄武岩熔体后的上地幔残留物。二辉橄榄岩中的矿物都处于平衡状态。用地质温度和压力计估算的二辉橄榄岩中的矿物平衡温度和压力分别为1100℃和1.5GPa。蓝宝石是碱性玄武岩浆早期结晶的产物,而且与单斜辉石、长石、石榴石和锆石巨晶共生。 相似文献