The blown sand disaster to the Tarim Desert Highway in Xinjiang,China

The Tarim Desert Highway in Xinjiang, China, the longest one in the world, has a length of 562 km, about 80% of which runs across, from north to south, the Taklimakan Desert. Obviously, the main problem of the road maintenance is the blown sand disaster. The research results showed: (1) the physical environment along the desert highway is characterized by strong winds, fine and loose ground materials, different dunes and so on, which provides the dynamical condition and material source for the formation of blown sand disaster to the road and its shelter system. Meanwhile, the trend and cross-section of the road and the structure of the shelter system, as damage objects, play important roles in the formation process of blown sand disaster; (2) the blown sand disaster to the shelter system is original from the intrusion of the drift sands and mobile dunes outside the shelter system, and the wind erosion and sand deposit caused by the air stream changes on the ground in the shelter system. The main damage object in the Tarim Desert Highway is the shelter system presently. The damage forms include wind erosion, sand burying and dune covering; and (3) the damaged length of the blocking sand fences is 83.7%, 88.4%, 72.4%, 72.8% and 40.3% and the damaged area of the straw checkerboard belts is 73.1%, 58.2%, 44.5%, 35.4% and 36.6%, in turn, in 5 different landform units from north to south, and, the disasters to fences and the straw checkerboard belts are 79.5% and 57.6% in the compound dunes while they are 64.6% and 37.7% in the interdunes respectively.

     

内蒙古东乌珠穆沁旗至辽宁东沟地学断面综合地球物理特征

综合地球物理探测与研究是地学断面的重要内容和基本依据,本断面的综合地球物理研究表明:这里的地壳可分为上、中、下三层,在某些部位中层地壳可进一步分为两层,其上层在断面东南端的辽河断陷东侧及燕山台褶带的义县、朝阳地区呈现为低速层;地壳厚度在断面东南端薄,为31—35km,而在西北端厚,达38—40km;辽河裂谷东侧存在壳内高导层,整个断面上地幔高导层发育,在辽河断陷及朝阳、义县地区反映为上地幔隆起区,在西拉木伦河一带出现落差达50km左右的台阶;确认析木断裂、郯—庐断裂北段、朝阳—北票断裂、赤峰—开原断裂和西拉木伦河等断裂为壳幔深断裂;发现海城地区、朝阳—北票地区及西拉木伦河地区为地壳与上地幔结构异常区,这里也正是地震较活跃的地区。     

<Emphasis Type="Italic">In-situ</Emphasis> trace element analyses and Pb-Pb dating of zircons in granulite from Huangtuling,Dabieshan by LAM-ICP-MS

It is revealed by CL images that there are multi-stage growth internal structures of zircons in the Huangtuling granulite, including the inherited zircons, protolith zircons, sector and planar zone zircons and retrograde zircons. In-situ trace element compositions and Pb-Pb ages have been analyzed by LAM-ICP-MS. The sector and the planar zone domains show typical trace element characteristics of granulite zircon (low Th, U, Th/U, total REEs, clear negative Eu anomalies, relatively depleted HREE and small differential degree between MREE and HREE, etc.), indicating that they formed during granulite-facies metamorphism. The protolith zircons have trace element characteristics of crustal zircon (high Th, U, Th/U, total REEs and enriched HREEs, etc.). 12 analyzed spots on granulite-facies domains give a weighted mean ²⁰⁷Pb/²⁰⁶Pb age of (2154±26) Ma (MSWD = 3.8), which is the best estimated age of granulite-facies metamorphism of this sample. The weighted mean ²⁰⁷Pb/²⁰⁶Pb age of 5 analyzed spots on protolith zircon domains is (2714 ± 22) Ma (MSWD = 1.4), which represents the protolith forming time. The discovery of ca. 3.4 Ga inherited zircon indicates that there are Palaeoarchean continental materials in this area. The interpretation of formation conditions and the ages of zircons can be constrained by simultaneous in-situ analysis of trace elements and ages.     

青海地区流体地球化学背景特征

青海省地处青藏构造块体东北部,境内各种次级活动断裂遍布,形成了地震活动强烈的构造背景,成为开展地震科研的天然实验场.该省地震地下流体测点主要分布在东北部地区,地震多,监测台站少,且省内流体地球化学研究程度低,有必要加强流体地球化学监测与研究工作.鉴于此,应用流体地球化学方法,开展深浅部流体特征的观测研究,通过分析流体组...     

贵州草海湿地不同生境周丛生物碳、氮、磷生态化学计量学

为深入了解湿地周丛生物碳(C)、氮(N)、磷(P)生态化学计量的变化规律及其影响因素,对贵州草海湿地4种不同生境(湖滨带、人工湿地、农田沟渠、污水处理厂)中周丛生物两个生长阶段(生长期和衰老期)的C、N、P生态化学计量学进行了研究.结果表明:水体营养指数依次为污水处理厂(51.55±4.50)＞农田沟渠(50.41±4...     

Hydraulic Conductivity from Nuclear Magnetic Resonance Logs in Sediments with Elevated Magnetic Susceptibilities

This study examined the application of slim-hole nuclear magnetic resonance (NMR) tools to estimate hydraulic conductivity (K_NMR) in an unconsolidated aquifer that contains a range of grain sizes (silt to gravel) and high and variable magnetic susceptibilities (MS) (10⁻⁴ to 10⁻² SI). A K calibration dataset was acquired at 1-m intervals in three fully screened wells, and compared to K_NMR estimates using the Schlumberger-Doll research (SDR) equation with published empirical constants developed from previous studies in unconsolidated sediments. While K_NMR using published constants was within an order of magnitude of K, the agreement, overprediction, or underprediction of K_NMR varied with the MS distribution in each well. An examination of the effects of MS on NMR data and site-specific empirical constants indicated that the exponent on T_2ML (n-value in the SDR equation, representing the diffusion regime) was found to have the greatest influence on K_NMR estimation accuracy, while NMR porosity did not improve the prediction of K. K_NMR was further improved by integrating an MS log into the NMR analyses. A first approach detrended T_2ML for the effects of MS prior to calculating K_NMR, and a second approach introduced an MS term into the SDR equation. Both were found to produce similar refinements of K_NMR in intervals of elevated MS. This study found that low frequency NMR logging with short echo times shows promise for sites with moderate to elevated MS levels, and recommends a workflow that examines parameter relationships and integrates MS logs into the estimation of K_NMR.     

Morphological responses of<Emphasis Type="Italic">Limnocythere inopinata</Emphasis> (Ostracoda) to hydrochemical environment factors

Living ostracod and hydrochemical samples were collected synchronously from more than 50 lakes and small water body in the eastern edge area of the Tibetan Plateau, Northern Tibetan, Southern Tibet and mid-Tibet. The comparison of the adult body length ofLimnocythere inopinata and hydrochemical parameters of their habitats shows that a quantitative relationship exists between the adult body length and salinity expressed as conductivity. An empirical formula to reconstruct paleosalinity is suggested first and applied to salinity reconstruction of CE-2 core from Cuoe Lake, Tibet. The method is verified by comparing its outcome with results of other environment reconstruction methods.     

Morphological responses ofLimnocythere inopinata (Ostracoda) to hydrochemical environment factors

Living ostracod and hydrochemical samples were collected synchronously from more than 50 lakes and small water body in the eastern edge area of the Tibetan Plateau, Northern Tibetan, Southern Tibet and mid-Tibet. The comparison of the adult body length ofLimnocythere inopinata and hydrochemical parameters of their habitats shows that a quantitative relationship exists between the adult body length and salinity expressed as conductivity. An empirical formula to reconstruct paleosalinity is suggested first and applied to salinity reconstruction of CE-2 core from Cuoe Lake, Tibet. The method is verified by comparing its outcome with results of other environment reconstruction methods.

     

人工神经网络及其在地震研究中的应用

简述了人工神经网络的发展历史,详述了Ｂ－Ｐ神经网络的基本原理,介绍了其在地震研究中的应用,文后对神经网络研究中应注意的问题进行了讨论。．     

The thermal history and uplift process of the Ouxidaban pluton in the South Tianshan orogen: Evidence from Ar-Ar and (U-Th)/He

The uplift and exhumation process in the Tianshan orogen since the late Paleozoic were likely related to the preservation of ore deposits. This study involved reconstructing the whole tectonic thermal history of the Ouxidaban pluton in central South Tianshan Mountains based on hornblende/plagioclase Ar-Ar and zircon/apatite(U-Th)/He methods. The thermal history and uplift process of central South Tianshan Mountains since the late Paleozoic were analyzed according to the results of previous works and cooling/exhumation rate features. The hornblende yields a plateau age of 382.6±3.6 Ma, and the plagioclase yields a weighted mean age of 265.8±4.9 Ma. The Ouxidaban pluton yields weighted mean zircon(U-Th)/He age of 185.8±4.3 Ma and apatite(U-Th)/He age of 31.1±2.9 Ma, respectively. Five stages of tectonic thermal history of South Tianshan Mountains since the late Paleozoic could be discriminated by the cooling curve and modeling simulation:(1) from the latest Silurian to Late Devonian, the average cooling rate of the Ouxidaban pluton was 7.84°C/Ma;(2) from the Late Devonian to the latest Middle Permian, the average cooling rate was about 2.07°C/Ma;(3) from the latest Middle Permian to the middle Eocene, the cooling rate decreased to about 0.68°C/Ma, suggesting that the tectonic activity was gentle at this time;(4) a sudden increase of the cooling rate(5.00°C/Ma) and the exhumation rate(0.17 mm/a), and crustal exhumation of ~1.83 km indicated that the Ouxidaban pluton would suffer a rapid uplift event during the Eocene(~46?35 Ma);(5) since the middle Eocene, the rapid uplift was sustained, and the average cooling rate since then has been 1.14°C/Ma with an exhumation rate of about 0.04 mm/a and an exhumation thickness of 1.33 km. The strong uplift since the Cenozoic would be related to a far-field effect from the Indian and Eurasian plates' collision. However, it was hysteretic that the remote effect was observed in the Tianshan orogenic belt.