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981.
吐木休克断裂位于塔里木盆地西部,是一条大型基底卷入型断裂构造带,构成塔里木盆地次级构造单元阿瓦提凹陷和巴楚断隆的分界。根据系统的地震资料解释,可以将吐木休克断裂分为西段、中段和东段3部分,各段构造特征有所差异。西段,为单一的基底卷入型高角度逆冲断层,倾向巴楚断隆; 中段,除倾向巴楚断隆的主冲断层外,倾向相反的反冲断层越来越清晰,楔状冲断构造的轮廓逐渐显现出来。同时,在断层上盘还发育第四纪正断层; 东段,倾向巴楚断隆的主冲断层,向上断至中寒武统,未断开中寒武统以上的地层,其冲断位移量完全为倾向阿瓦提凹陷的反冲断层所吸收,形成典型的楔状冲断构造。根据地震资料解释,认为吐木休克断裂带主要存在两期断裂构造:深部高角度基底卷入型逆冲断裂带和其上叠加的浅部正断层。前者形成于库车组沉积前,在库车组沉积期间持续活动,并在新近纪晚期定型; 后者是本次研究首次发现的,形成于第四纪早中期,仅发育在吐木休克断裂带的中部。 相似文献
982.
983.
Early Neoproterozoic granulite facies metamorphism of mafic dykes from the Vestfold Block,east Antarctica 总被引:2,自引:0,他引:2
Proterozoic mafic dykes from the southwestern Vestfold Block experienced heterogeneous granulite facies metamorphism, characterized by spotted or fractured garnet‐bearing aggregates in garnet‐absent groundmass. The garnet‐absent groundmass typically preserves an ophitic texture composed of lathy plagioclase, intergranular clinopyroxene and Fe–Ti oxides. Garnet‐bearing domains consist mainly of a metamorphic assemblage of garnet, clinopyroxene, orthopyroxene, hornblende, biotite, plagioclase, K‐feldspar, quartz and Fe–Ti oxides. Chemical compositions and textural relationships suggest that these metamorphic minerals reached local equilibrium in the centre of the garnet‐bearing domains. Pseudosection calculations in the model system NCFMASHTO (Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3) yield P–T estimates of 820–870 °C and 8.4–9.7 kbar. Ion microprobe U–Pb zircon dating reveals that the NW‐ and N‐trending mafic dykes were emplaced at 1764 ± 25 and 1232 ± 12 Ma, respectively, whereas their metamorphic ages cluster between 957 ± 7 and 938 ± 9 Ma. The identification of granulite facies mineral inclusions in metamorphic zircon domains is also consistent with early Neoproterozoic metamorphism. Therefore, the southwestern margin of the Vestfold Block is inferred to have been buried to depths of ~30–35 km beneath the Rayner orogen during the late stage of the late Mesoproterozoic/early Neoproterozoic collision between the Indian craton and east Antarctica (i.e. the Lambert Terrane or the Ruker craton including the Lambert Terrane). The lack of penetrative deformation and intensive fluid–rock interaction in the rigid Vestfold Block prevented the nucleation and growth of garnet and resulted in the heterogeneous granulite facies metamorphism of the mafic dykes. 相似文献
984.
通过对桂林地质构造和岩溶建造的研究,并对岩溶洼地、洞穴发育特征进行分析,认为它们在发生、发展上具有成生的内在联系,从而反映在时空方面具有特定的关系。 这些关系集中表现在岩溶洼地、洞穴是岩溶水沿断裂、裂隙溶蚀、侵蚀扩大、改造、堆积、再改造的结果。其规律性主要反映在方向性、等距性、继承性、成层性及形态关系等几个方面。 实践表明,研究岩溶发育规律,要对构造控制因素进行分析,必须从构造形迹鉴别入手,分析其成生联系、体系归属,了解地质构造的发生。发展阶段和序次,并以此和岩溶岩系(建造)为依据,联系成岩环境(特征)和水文地质条件进行综合分析,才能客观反映构造的控制规律。 相似文献
985.
大别山北麓梅山群中韧性剪切带变形特征及形成机制 总被引:1,自引:0,他引:1
梅山群为分布于北淮阳地区位于佛子岭群之下、逆掩于晚泥盆世—石炭纪杨山煤系和中侏罗统红层之上的一套中—浅变质岩系,在其中、上部发育NW走向的韧性剪切带,产状与区域片理一致。对韧性剪切带及其变形岩石———糜棱岩的宏微观构造研究表明,韧性剪切变形发生于区域变质岩形成之后,具有右旋剪切的运动特点,反映大别山地块向北仰冲过程中所派生的侧向滑移作用 相似文献
986.
Zi-Xiang Chen Lei Yu Wei-Guo Liu Michael H. W. Lam Gui-Jian Liu Xue-Bin Yin 《Environmental Earth Sciences》2014,71(1):217-223
The stable isotope nitrogen-15 (15N) is a robust indicator of nitrogen (N) source, and the joint use of δ15N and δ18O–NO3 ? values can provide more useful information about nitrate source discrimination and N cycle process. The δ15N and δ18O–NO3 ? values, as well as major ion tracers, from Taihu Lake in east China were investigated to identify the primary nitrate sources and assess nitrate biogeochemical process in the present study. The results show that the nitrate concentration in West Taihu Lake (WTL) was generally higher than those in East Taihu Lake (ETL) and its upstream inflow rivers. The NO3 ?/Cl? value combined with mapping of δ15N–NO3 ? and NO3 ? concentration suggest that the mixing process should play a major effect in WTL, and denitrification was the dominant N transformation process in WTL. A linear relationship of close to ~1: 2 was observed between δ15N–NO3 ? and δ18O–NO3 ? values in WTL, confirming the occurrence of denitrification in WTL. The δ15N–NO3 ? data imply that sewage and manure were the principal nitrate sources in WTL and its feeder rivers, while the nitrate in ETL might derive from soil organic nitrogen and atmospheric deposition. The δ18O–NO3 ? data indicate most of nitrate from microbial nitrification of organic nitrogen matter possibly make a significant contribution to the lake. 相似文献
987.
988.
989.
新疆阿尔泰克因布拉克铜锌矿床地质特征及成矿作用 总被引:3,自引:1,他引:3
克因布拉克中型铜锌矿床赋存于早二叠世花岗岩外接触带的上志留统-下泥盆统康布铁堡组黑云石英片岩、变质石英砂岩中。矿床的形成经历了夕卡岩期、热液期和表生期,铜锌矿主要形成于热液期。矿石中石英和方解石流体包裹体划分为H_2O-NaCl型和H_2O-CO_2(±CH_4/N_2)-NaCl型。成矿温度变化于146~448℃,在170℃、270℃和350℃出现峰值;流体盐度变化于0.2%~46.9%NaCl_(eq),峰值为1.5%NaCl_(eq)和5.5%NaCl_(eq);流体的密度0.55~1.19g/cm~3。硫化物的δ~(34)S集中变化于-8.4‰~1.9‰,峰值为0‰,表明硫来自岩浆。石英和方解石δD_(SMOW)介于-130‰~-79‰,δ~(18)O_(SMOW)值介于8.0‰~11.6‰,δ~(18)O_(H2O)值为-1.7‰~4.43‰,表明成矿流体主要是岩浆水,混合大气降水。方解石中δ~(13)C_(PDB)变化于-5.3‰~-1.1‰,暗示碳来自花岗质岩浆。成矿时代为早中二叠世,成矿作用与花岗质岩浆期后的热液活动有关。 相似文献
990.
Response of groundwater chemistry to water deliveries in the lower reaches of Tarim River,Northwest China 总被引:2,自引:0,他引:2
Yongjin Chen Kefa Zhou Yaning Chen Weihong Li Jiazhen Liu Tao Wang 《Environmental Geology》2008,53(6):1365-1373
In this paper, we analysed the monitored data from nine groundwater-monitoring transects in the lower reaches of Tarim River
during the five times of stream water deliveries to the river transect where the stream flow ceased. The results showed that
the groundwater depth in the lower reaches of Tarim River rose from −9.30 m before the conveyances to −8.17 and −6.50 m after
the first and second conveyances, −5.81 and −6.00 m after the third and fourth the conveyance, and −4.73 m after the fifth.
The horizontal extent of groundwater recharge was gradually enlarged along both sides of the channel of conveyance, i.e.,
from 250 m in width after the first conveyance to 1,050 m away from the channel after the fourth delivery. With the rising
groundwater level, the concentrations of major anions Cl−, SO42− and cations Ca2+, Mg2+, Na+, as well as total dissolved solids (TDS) in groundwater underwent a significant change. The spatial variations in groundwater
chemistry indicated that the groundwater chemistry at the transect near Daxihaizi Reservoir changed earlier than that farther
from it. In the same transect, the chemical variations were earlier in the monitoring well close to watercourse than that
farther away from the stream. In general, the concentration of the major ions and TDS at each monitoring well increased remarkably
when the water delivery started, and decreased with the continued water delivery, and then increased once again at the end
of the study period. Hence, the whole study period may be divided into three stages: the initial stage, the intermediate stage
and the later stage. According to the three stages of groundwater chemistry reaction to water delivery and the relationships
between groundwater chemical properties and groundwater depths, we educe that under the situation of water delivery, the optimum
groundwater depth in the lower reaches of the Tarim River should be −5 m. 相似文献