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651.
龙岗地区陇川运动-华力西运动间造成整个古生代地层缺失,中上三叠统直接覆于下元古界哀牢山岩群、大红山岩群等基底岩系之上,本文称为“超级不整合”。华力西期-喜马拉雅期历次地壳事件在“超级不整合”接触带形成“矿质”的“浪淘砂”式、叠次‘堆积’作用,对该区金成矿有决定性作用,先后发现小水井与大龙潭两个典型金矿床。前者为“地下水热卤水溶滤中低温热液蚀变角砾岩微粒浸染型金矿床”,可类比为“卡林型”;后者为“原生沉积地下热水溶滤中低温热液蚀变砂砾岩微粒-粗粒型金矿床”,为该区首次发现的新类型。 相似文献
652.
2-D Crustal thermal structure along Thuadara-Sindad DSS profile across Narmada-Son lineament,central India 总被引:1,自引:0,他引:1
Central India is traversed by a WSW-ENE trending Narmada-Son lineament (NSL) which is characterized by the presence of numerous
hot springs, feeder dykes for Deccan Traps and seismicity all along its length. It is divided in two parts by the Barwani-Sukta
Fault (BSF). To the west of this fault a graben exists, whereas to the east the basement is uplifted between Narmada North
Fault (NNF) and Narmada South Fault (NSF). The present work deals with the 2-D thermal modeling to delineate the crustal thermal
structure of the western part of NSL region along the Thuadara-Sindad Deep Seismic Sounding (DSS) profile which runs almost
in the N-S direction across the NSL. Numerical results of the model reveal that the conductive surface heat flow value in
the region under consideration varies between 45 and 47mW/m2. Out of which 23mW/m2 is the contribution from the mantle heat flow and the remaining from within the crust. The Curie depth is found to vary between
46 and 47 km and is in close agreement with the earlier reported Curie depth estimated from the analysis of MAGSAT data. The
Moho temperature varies between 470 and 500°C. This study suggests that this western part of central Indian region is characterized
by low mantle heat flow which in turn makes the lower crust brittle and amenable to the occurrence of deep focused earthquakes
such as Satpura (1938) earthquake. 相似文献
653.
Wang Yong Hou Zengqian Mo Xuanxue Dong Fangliu Bi Xianmei Zeng Pusheng 《Frontiers of Earth Science》2007,1(3):322-332
More than 140 middle-small sized deposits or minerals are present in the Weishan-Yongping ore concentration area which is
located in the southern part of a typical Lanping strike-slip and pull-apart basin. It has plenty of mineral resources derived
from the collision between the Indian and Asian plates. The ore-forming fluid system in the Weishan-Yongping ore concentration
area can be divided into two subsystems, namely, the Zijinshan subsystem and Gonglang arc subsystem. The ore-forming fluids
of Cu, Co deposits in the Gonglang arc fluid subsystem have δD values between −83.8‰ and −69‰, δ18O values between 4.17‰ and 10.45‰, and δ13C values between −13.6‰ and 3.7‰, suggesting that the ore-forming fluids of Cu, Co deposits were derived mainly from magmatic
water and partly from formation water. The ore-forming fluids of Au, Pb, Zn, Fe deposits in the Zijinshan subsystem have δD
values between −117.4‰ and −76‰, δ18O values between 5.32‰ and 9.56‰, and Δ13C values between −10.07‰ and −1.5‰. The ore-forming fluids of Sb deposits have δD values between −95‰ and −78‰, δ18O values between 4.5‰ and 32.3‰, and Δ13C values between −26.4‰ and −1.9‰. Hence, the ore-forming fluids of the Zijinshan subsystem must have been derived mainly
from formation water and partly from magmatic water. Affected by the collision between the Indian and Asian plates, ore-forming
fluids in Weishan-Yongping basin migrated considerably from southwest to northeast. At first, the Gonglang arc subsystem with
high temperature and high salinity was formed. With the development of the ore-forming fluids, the Zijinshan subsystem with
lower temperature and lower salinity was subsequently formed.
Translated from Mineral Deposits, 2006, 25(1): 60–70 [译自: 矿床地质] 相似文献
654.
Wenjun Yong E. Dachs A. C. Withers E. J. Essene 《Physics and Chemistry of Minerals》2007,34(2):121-127
A multi-anvil device was used to synthesize 24 mg of pure γ-Fe2SiO4 crystals at 8.5 GPa and 1,273 K. The low-temperature heat capacity (C
p) of γ-Fe2SiO4 was measured between 5 and 303 K using the heat capacity option of a physical properties measurement system. The measured
heat capacity data show a broad λ-transition at 11.8 K. The difference in the C
p between fayalite and γ-Fe2SiO4 is reduced as the temperature increases in the range of 50–300 K. The gap in C
p data between 300 and 350 K of γ-Fe2SiO4 is an impediment to calculation of a precise C
p equation above 298 K that can be used for phase equilibrium calculations at high temperatures and high pressures. The C
p and entropy of γ-Fe2SiO4 at standard temperature and pressure (S°298) are 131.1 ± 0.6 and 140.2 ± 0.4 J mol−1 K−1, respectively. The Gibbs free energy at standard pressure and temperature (ΔG°
f,298) is calculated to be −1,369.3 ± 2.7 J mol−1 based on the new entropy data. The phase boundary for the fayalite–γ-Fe2SiO4 transition at 298 K based on current thermodynamic data is located at 2.4 ± 0.6 GPa with a slope of 25.4 bars/K, consistent
with extrapolated results of previous experimental studies. 相似文献
655.
In marine strata from Sinian to Middle Triassic in South China, there develop four sets of regional and six sets of local
source rocks, and ten sets of reservoir rocks. The occurrence of four main formation periods in association with five main
reconstruction periods, results in a secondary origin for the most marine gas pools in South China. To improve the understanding
of marine gas pools in South China with severely deformed geological background, the dominant control factors are discussed
in this paper. The fluid sources, including the gas cracked from crude oil, the gas dissolved in water, the gas of inorganic
origin, hydrocarbons generated during the second phase, and the mixed pool fluid source, were the most significant control
factors of the types and the development stage of pools. The period of the pool formation and the reconstruction controlled
the pool evolution and the distribution on a regional scale. Owing to the multiple periods of the pool formation and the reconstruction,
the distribution of marine gas pools was complex both in space and in time, and the gas in the pools is heterogeneous. Pool
elements, such as preservation conditions, traps and migration paths, and reservoir rocks and facies, also served as important
control factors to marine gas pools in South China. Especially, the preservation conditions played a key role in maintaining
marine oil and gas accumulations on a regional or local scale. According to several dominant control factors of a pool, the
pool-controlling model can be constructed. As an example, the pool-controlling model of Sinian gas pool in Weiyuan gas field
in Sichuan basin was summed up. 相似文献
656.
采用可以有效控制环境因子的室内土壤培养试验,初步研究了科尔沁沙地30种植物叶凋落物的CO2释放量及释放速率。结果表明:①在28 d培养期内,不同植物叶凋落物释放的CO2量差异很大,其中,多年生植物叶凋落物CO2释放量平均值大于一年生植物,但二者之间的差异不显著;禾本科植物叶凋落物CO2释放量平均值明显小于其他植物,二者之间呈显著差异。②在28 d培养期内,不同植物叶凋落物每四天CO2释放速率差异很大。一年生与多年生植物叶凋落物28 d内每四天释放CO2的速率无显著差异;禾本科与其他植物叶凋落物每四天释放CO2的速率在培养的前16 d差异呈显著,而后差异消失。③植物叶凋落物的全碳含量,氮含量,C/N,灰分/N及灰分含量不同造成CO2释放量及释放速率的差异。叶凋落物28 d释放CO2的量与叶凋落物初始碳含量及灰分含量均无相关关系,与叶凋落物初始氮含量呈显著正相关,与叶凋落物C/N及灰分/N呈显著负相关。叶凋落物培养期内每四天释放CO2的速率与叶凋落物初始碳含量无相关关系;叶凋落物0\_20天释放CO2的速率与叶凋落物初始氮含量呈显著正相关,与叶凋落物C/N呈显著负相关;叶凋落物9\_28天CO2释放速率与灰分/N呈显著负相关;培养后期(17\_28天)的CO2释放速率与灰分含量呈显著负相关。 相似文献
657.
通过对青藏高原崇测冰帽一支18.70m冰芯中Cl^-、SO4^2-离子含量变化的分析表明,20世纪90年来Cl^-、SO4^2-离子含量在波动中呈下降趋势,两种离子的周期性波动变化相似,20世纪晚期比早期和中期的波动幅度小,总体上离子含量逐渐减少与温度在波动中上升相一致,但每一次温度的升高与离子含量的下降并非一一对应。陆源物质和青藏高原上的盐湖是冰芯中Cl^-、SO4^2-离子的主要贡献者。揭示了研究地区大气成分和环境变化与气候变化的关系及亚洲粉尘在全球环境变化中的源区地位。 相似文献
658.
659.
Marc Rütschlin Johannes H. Cloete Iain M. Mason Keith D. Palmer 《Journal of Applied Geophysics》2007,62(4):354-360
A new measurement technique enables the complex dielectric properties of the geological strata comprising the UG1–UG2 (Upper Group 1–Upper Group 2) unit of the Bushveld Complex in South Africa to be determined with unprecedented detail at radio frequencies (RF). Results of non-destructive laboratory measurements of representative diamond drill core samples from the UG1–UG2 unit are presented at 25 MHz. These data establish that the UG1 and UG2 chromitite layers are embedded in rock strata (norite, pyroxenite and anorthosite) which are translucent in the HF spectral band, whereas the chromitite layers themselves exhibit significant velocity contrast, making them good radar reflectors. The data presented here is useful for calibration of the radar system, and for predicting the range and resolution performance of borehole radars operating in both the hanging and footwalls of the economically important platiniferous UG2 reef. 相似文献
660.
Abstract Trace-element compositions of jadeite (±omphacite) in jadeitites from the Itoigawa-Ohmi district of Japan, analyzed by a laser-ablation inductively coupled plasma mass spectrometry technique showed chemical zoning within individual grains and variations within each sample and between different samples. Primitive mantle-normalized patterns of jadeite in the samples generally showed high large-ion lithophile element contents, high light rare earth element/heavy rare earth element ratios and positive anomalies of high field strength elements. The studied jadeitites have no signatures of the protolith texture or mineralogy. Shapes and distributions of minerals coupled with chemical zoning within grains suggest that the jadeitites were formed by direct precipitation of minerals from aqueous fluids or complete metasomatic modification of the precursor rocks by fluids. In either case, the geochemical characteristics of jadeite are highly affected by fluids enriched in both large-ion lithophile elements and high field strength elements. The specific fluids responsible for the formation of jadeitites are related to serpentinization by slab-derived fluids in subduction zones. This process is followed by dissolving high field strength elements in the subducting crust as the fluids continue to circulate into the subducting crusts and serpentinized peridotites. The fluids have variations in chemical compositions corresponding to various degrees of water–rock interactions. 相似文献