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121.
内蒙古突泉县牤牛海地区发育超镁铁质岩,主要岩石类型为蛇纹石化橄榄岩、辉石橄榄岩、异剥辉石橄榄岩和蛇纹岩,局部蛇纹岩中可见显微鬣刺假象结构,包括蛇纹石呈假像的柱状中空骸晶结构、鱼骨状或羽状结构。岩石化学具有高镁(w(MgO)为33.63%~39.44%)、铬(2 200×10~(-6)~17 200×10~(-6))、镍(1 900×10~(-6)~3 000×10~(-6)),高CaO/Al_2O_3(0.56~39.01,平均为7.05),低钛(w(TiO_2)为0.01%~0.02%)、低铝(w(Al2O3)为0.03%~0.36%)、低碱(w(K_2O+Na_2O)为0.03%~0.65%)特征,类似科马提岩;Mg#值(平均为87)与纯橄榄岩(86)接近;稀土元素(w(∑REE)为0.32×10~(-6)~2.79×10~(-6))明显低于大洋脊含量,轻稀土富集(LREE/HREE为2.80~16.68),Eu正异常明显(δEu为0.59~4.84);微量元素富集大离子亲石元素(LILE)Rb、Ba、Sr,亏损高场强元素(HFSE)Nb、P等。说明超镁铁质岩石岩浆源自亏损软流圈地幔,并受到俯冲流体交代作用,形成于岛弧环境。牤牛海超镁铁质岩与西部包括突泉围场、好老鹿场、超日海乌拉、梅劳特乌拉、苏尼特左旗二道井一带超镁铁质岩共同构成一条近东西向展布的超镁铁质岩(蛇绿岩)带,通过地质建造分析,认为该构造带可能为华北板块与西伯利亚板块最终缝合带。 相似文献
122.
Kangding geothermal area is located in the western Sichuan, belonging to southeastern margin of Tibetan Plateau. Similar to world-renowned south Tibetan and western Yunnan geothermal belt, western Sichuan has intensive surface thermal manifestations including boiling and hot springs. The emerging temperature of thermal waters ranges from 47 to 79 °C with total dissolved solids lying between 899 and 2550 mg/L. δ2H–δ18O isotopes indicate a meteoric source for the thermal waters and a significant positive oxygen-18 shift in the southern region. It is suggested that southern thermal waters experienced stronger water–rock interaction and are closer to thermodynamic equilibrium, which is also proved by the water type classification. The reservoir temperature calculated by empirical and theoretical chemical thermometry is 180–225 °C for the north and 225–310 °C for the south. Evidences of hydrogeochemistry, stable isotopes, geothermometry and radiocarbon dating indicate that southern region of Kangding area shows greater geothermal potential than the northern region. In addition, based on the hydrogeochemical modeling of mineral saturation, underlying problem of scaling is likely to occur in the study area. According to the results of reservoir temperature, south Kangding sub-district has greater potential in geothermal power generation and development than northern Kangding. Therefore, further exploration and drilling work should give priority to the south Kangding area. 相似文献
123.
对湖北郧县辽瓦店剖面的沉积学特征及磁化率、粒度、Rb、Sr含量等理化指标进行了研究。结果表明:辽瓦店剖面自下而上具有马兰黄土(L1)-过渡层(Lt)-古土壤(S0)-全新世黄土(L0)-表土(TS)地层序列;不同地层单元的风化成壤差异明显,其成壤强弱顺序为古土壤S0成壤最强、全新世黄土L0和过渡层Lt次之、马兰黄土L1最弱。成壤强弱的变化揭示出该区晚更新世末期(11 500 a BP以前)气候干冷,全新世早期(11 500~8 500 a BP)气候处于晚更新世干冷向全新世中期暖湿的过渡阶段,全新世中期(8 500~3 100 a BP)气候最为温暖湿润,全新世晚期(3 100 a BP以来)气候转为干冷且逐渐恶化的变化过程。 相似文献
124.
With deep sea petroleum explorations become more and more popular,some geological phenomena have emerged:extension of lower crust and upper crust is inhomogeneous;shelf break has been moved rapidly after crustal stretching.These geological phenomena are important to the continental margin evolution.To investigate the thinning of the whole crust and the contribution of the upper crust versus the lower crust to the crustal stretching since the Cenozoic,we calculated the stretching factors of the upper and the lower crust based on the 13 seismic lines in the Baiyun Sag from CNOOC.The results indicated that the whole crustal thickness decreases seaward while the whole crustal stretching factor increases from shelf to slope.Our calculations showed that the lower crustal stretching factor is higher than that of the upper crust in the Baiyun Sag.In the Cenozoic,deformation of the Baiyun Sag is controlled mainly by ductile shearing rather than brittle shearing.Based on the numerical modeling,we can conclude the initial crust in the Baiyun Sag is thermally attenuated.The stretching factor(β)of the lower crust increases from the north to the south of the continental margin,indicating two stretching centers:the Baiyun Sag and the Liwan Sag.The geometry of the shelf break and theβisoline trap have the similar trend in 23.8 and 13.8 Ma,both located in the intense deforming zone of the lower crust,and therefore we conclude the stretching and flowing of the lower crust cause the displacement of the shelf break before and after 23.8 Ma. 相似文献
125.
Geochemistry and genesis of authigenic pyrite from gas hydrate accumulation system in the Qilian Mountain permafrost,Qinghai, northwest China 总被引:2,自引:0,他引:2
PingKang Wang YouHai Zhu ZhenQuan Lu Xia Huang ShouJi Pang Shuai Zhang ShaoQing Jiang QingHai Li KaiLi Yang Bing Li 《中国科学:地球科学(英文版)》2014,57(9):2217-2231
A type of authigenic pyrites that fully fill or semi-fill the rock fractures of drillholes with gas hydrate anomalies are found in the Qilian Mountain permafrost; this type of pyrite is known as “fracture-filling” pyrite. The occurrence of “fracture-filling” pyrite has a certain similarity with that of the hydrate found in this region, and the pyrite is generally concentrated in the lower part of the hydrate layer or the hydrate anomaly layer. The morphology, trace elements, rare earth elements, and sulfur isotope analyses of samples from drillhole DK-6 indicate that the “fracture-filling” pyrites are dominated by cubic ones mainly aligned in a step-like fashion along the surfaces of rock fractures and are associated with a circular structure, lower Co/Ni and Sr/Ba, lower ΣREE, higher LREE, significant Eu negative anomalies, and Δ34SCDT positive bias. In terms of the pyrites’ unique crystal morphology and geochemical characteristics and their relationship with the hydrate layers or abnormal layers, they are closely related with the accumulation system of the gas hydrate in the Qilian Mountain permafrost. As climate change is an important factor in affecting the stability of the gas hydrate, formation of fracture-filling pyrites is most likely closely related to the secondary change of the metastable gas hydrate under the regional climate warming. The distribution intensity of these pyrites indicates that when the gas hydrate stability zone (GHSZ) is narrowing, the hydrate decomposition at the bottom of the GHSZ is stronger than that at the top of the GHSZ, whereas the hydrate decomposition within the GHSZ is relatively weak. Thus, the zone between the shallowest and the deepest distribution of the fracture-filling pyrite recorded the largest possible original GHSZ. 相似文献
126.
127.
对汉江上游进行野外实地详细调查,在湖北省郧县尚家河台地前沿发现了典型的全新世黄土-古土壤沉积剖面,通过粒度、磁化率、吸湿水和烧失量分析表明,黏粒、细粉砂、磁化率、吸湿水和烧失量在古土壤层S0出现高值,在L1、Lt、L0为低值;而粗粉砂、细砂粒和粗砂粒在S0为低值,在L1、Lt、L0为高值。这些指标的变化说明了全新世以来的气候和成壤环境的变化特征,即在古土壤S0形成时期,气候温暖湿润,成壤作用非常强烈;黄土堆积时期气候相对干旱,成壤作用较弱。 相似文献
128.
Environmental significance of snowpit chemistry in the typical monsoonal temperate glacier region,Baishui glacier no. 1, Mt Yulong,China 总被引:1,自引:0,他引:1
Li Zongxing He Yuanqing Pang Hongxi Wilfred H. Theakstone Zhang Ningning He Xianzhong Wang Shijing Pu Tao Du Jiankuo 《Environmental Geology》2009,58(6):1319-1328
Samples were collected from two snowpits in Baishui glacier no. 1, Mt Yulong, China, in May 2006. Snowpit chemistry was studied,
using ion tracer techniques, HYSPLIT model, factor analysis, correlation and trend analysis. It indicated that total cation
concentration is higher in 4,900-m snowpit than in 4,750-m snowpit, whereas total anion concentration is higher in 4,750-m
snowpit. Cations, especially Ca2+, dominate ionic concentrations in Baishui glacier no. 1. According to correlation analysis and factor analysis, ions can
be categorized as follows: Cl− and NO3
− as Group 1, SO4
2− as Group 2, Mg2+ and Ca2+ as Group 3, Na+ as Group 4, K+ as Group 5. Contribution made by terrestrial dust to ionic concentration accounts for 52.27, 100, 99.36, 98.91, 96.16 and
99.97% of Cl−, NO3
−, SO4
2−, K+, Mg2+ and Ca2+, respectively, in 4,900-m snowpit, and for 64.00, 100, 99.57, 98.63, 96.25 and 99.97% in 4,750-m snowpit. Local dust is the
principal source of snowpit chemical components. Pollutants brought from industrial areas of South Asia, Southeast Asia and
South China by monsoonal circulation also makes some contribution to anion concentrations, but pollution associated with human
activities makes a very slight contribution in study area. The chemical characteristics of two snowpits are different owing
to the difference of deposition mechanism and local environment in different altitudes. 相似文献
129.
通过对内蒙古额济纳盆地小狐山剖面沉积物中酸溶组分稀土元素含量及其相关指标、分布模式的分析,讨论了剖面中稀土元素指标δCe-ΣREE与沉积相、沉积环境之间的关系。分析结果表明剖面沉积物酸溶组分中稀土元素丰度均值为7.24μg/g(不包括Y),其中LREE含量占稀土总量的88.67%; 且各层的稀土分布模式均为轻稀土适度富集缓右倾斜型、Eu呈负异常模式,但各相位地层的LREE富集程度与分配模式存在差异。由于小狐山剖面中沉积地层的自身岩性、沉积粒径、矿物结构组成以及气候环境变化等因素均可能会引起REE分异。因此,通过δCe-ΣREE图并结合三次回归曲线,可以很好地将不同沉积相得物质有效的区分开来。小狐山剖面除极少数的几个样品(水下沉积砂)之外,其余的均落在三次多项式回归曲线上部; 而风成砂层则几乎全部落在回归曲线之下; 此外,对于风沙-河流作用下的混合样品也有较好识别,河流过渡相的样品则分布在曲线上或与之相邻近。此研究结果得到了柴达木贝壳堤沉积物的REE数据的验证,运用此方法可以为直观的判别剖面中的不同沉积相,并为定量化划分地层提供依据。 相似文献
130.
Wu Xiangjie Pang Xiong Shi Hesheng He Min Shen Jan Zhang Xiangtao Hu Dengke 《中国地质大学学报(英文版)》2009,20(1)
To study the deep dynamic mechanism leading to the difference in rifting pattern and basin structure from shelf to oceanic basin in passive continental margin,we constructed long geological sections across the shelf,slope and oceanic basin using new seismic data.Integrated gravity-magnetic inversion and interpretation of these sections were made with the advanced dissection method.Results show that the basement composition changes from intermediate-acid intrusive rocks in the sheff to intermediate-basic rocks in the slope.The Moho surface shoals gradually from 31 km in the sheff to 22.5 km in the uplift and then 19 km in the slope and finally to 13 km in the oceanic basin.The crust thickness also decreases gradually from 30 km in the northern fault belt to 9 km in the oceanic basin.The crustal stretching factor increases from the shelf toward the oceanic basin,with the strongest extension under the sags and the oceanic basin.The intensity of mantle upwelling controlled the style of basin structures from sheff to oceanic basin.In the Zhu 1 depression on the shelf,the crust is nearly normal,the brittle and cold upper crust mainly controlled the fault development;so the combinative grabens with single symmetric graben are characteristic.In the slope,the crust thinned with a large stretching factor,affected by the mantle upwelling.The ductile deformation controlled the faults,so there developed an asymmetric complex graben in the Baiyun (白云) sag. 相似文献