金川Cu-Ni-PGE硫化物矿床成矿过程稀有气体同位素组成示踪     

胡沛青  张铭杰  汤庆艳  叶先仁  汤中立  李文渊 《岩石学报》2010,26(11):3375-3386

稀有气体同位素在示踪成矿作用流体来源方面具有独特优势。本文应用熔融质谱法测定了金川Cu-Ni-PGE硫化物矿床23个硅酸盐矿物和金属硫化物单矿物的He、Ne和Ar丰度和同位素组成。结果表明,硅酸盐矿物的3He/4He比值(0.239Ra)略低于硫化物(平均0.456Ra),且从橄榄石(平均0.291Ra)、斜方辉石(0.215Ra)到单斜辉石(0.174Ra)逐渐降低,20Ne/22Ne-21Ne/22Ne分布于MORB与大陆地壳演化线之间,扣除放射性成因4He*和40Ar*后橄榄石和辉石中3He/4He和40Ar/36Ar接近岩石圈地幔组成。He、Ne和Ar同位素组成示踪表明成矿岩浆中存在岩石圈地幔(SCLM)、地壳(CC)和大气饱和流体(ASW)三种端元成分,硫化物熔体的分离发生在岩浆结晶分异的早期。岩石圈地幔部分熔融形成的成矿初始岩浆经历了两阶段的演化。在深部岩浆房高温成矿岩浆同化围岩引入地壳混染组分,促使硫饱和及硫化物熔体的熔离,同时形成具有壳幔混合特征的混合岩浆组分(MC),上升至上部岩浆房后混入较高比例的大气饱和流体,进一步促使硫饱和及浸染状硫化物就地熔离堆积。  相似文献   

大气环境氮同位素示踪及生物监测   总被引：1，自引：0，他引：1       下载免费PDF全文

肖化云  刘丛强 《地学前缘》2010,17(2):417

大气中氮的转化、迁移和沉降等大气过程与地表氮的生物地球化学循环密切相关。氮同位素对大气氮源和氮的大气化学过程的定量研究已引起广泛关注。本文对大气不同氮源的同位素特征、氮在大气过程中的同位素分馏机制以及如何定量化大气氮过程的方法进行了简要阐述,并介绍了苔藓氮同位素作为一种新的研究手段在示踪大气氮源和大气氮过程等方面取得的新进展。对国内开展的有关大气氮同位素以及苔藓氮同位素方面的工作进行了重点介绍。  相似文献   

Soft‐bottom macrobenthic communities of Manukau Harbour,New Zealand   总被引：1，自引：1，他引：0  

K. R. Grange 《新西兰海洋与淡水研究杂志》2013,47(3):315-329

A survey of the macrobenthos at 42 stations in the channels and subtidal sandflats in Manukau Harbour, Auckland, revealed four biotic associations; although referred to as communities, they are not equivalent to Peterson‐type communities since they are not particularly discrete and there is some overlap in species composition. The similarity in species between stations was measured by percentage similarity coefficients using Jaccard's coefficient for presence‐absence data and Czekanowski's coefficient for log‐transformed quantitative data. Stations were grouped in dendrograms by group‐average sorting which allowed re‐arrangement of the similarity matrices into trellis diagrams.

Dominant species in each of the four groups of stations were ranked by calculating a ‘community score’ for each, based on its abundance, fidelity, and bioindex value within the group. Each of the four groups was found to support a unique group of species and these are considered as representing four communities. Two indicator species in each community were identified from the highest community scores: Group 1, the Microcosmus/Nolomithrax community — associated with a coarse sediment of dead bivalve shells and small rocks in shallow water. It has high species diversity indices; Group 2, the Halicarcinus/Bugula community— associated with a relatively coarse sediment of dead shells, grit, and little sand in deep water in the main channels; Group 3, the Amalda/Myadora community—associated with fine sand with mud or shell grit in shallow parts of the channels; and Group 4, the Fellaster/Pagurus community — associated with ironsand in shallow water in the outer harbour. It has low species diversity indices.  相似文献   

高程异常扰动源及均衡异常影响分析     

刘缵武  刘世晗 《海洋测绘》2013,33(5):7-9

通过分析高程异常的扰动源,探究地形均衡扰动物质引起的均衡高程异常,说明全球许多高原地区的高程异常为负值的主要原因在于地球深部的密度异常,而非地球表面突起的扰动物质和相应地壳均衡部分的扰动物质。一般地,地形及均衡部分对高程异常的影响不足以完全反映高程异常的符号,在许多高原地区的高程异常为负值,可能在深层地幔有大尺度负的扰动质量进行补偿。  相似文献   

Models-3模式中增加移动源清单对模拟效果的影响   总被引：1，自引：0，他引：1       下载免费PDF全文

王扬锋  马雁军  侯波  李炳昆  刘凤辉  任万辉 《气象与环境学报》2009,25(6):18-22

采用空气质量模式Models-3,在原有点源和面源污染源输入清单的基础上,加入移动污染源,对辽宁地区2004年12月24—27日大气污染物时空分布进行数值模拟。结果表明,加入移动污染源后,辽宁主要城市污染物SO₂、NO₂和PM₁₀模拟效果有所提高,NO₂模拟效果提高最为明显;从总体模拟效果来看, SO₂和NO₂模拟效果较好,而PM₁₀模拟值相对较差。  相似文献   

大兴安岭北部比利亚谷铅锌矿黄铁矿Re-Os同位素年龄及He-Ar同位素地球化学特征     

马玉波  张勇  李立兴  邢树文  张增杰  张彤  肖克炎  王海坡  范建福 《地质学报》2022,96(4):1265-1278

比利亚谷铅锌矿位于海拉尔-根河中生代火山盆地北西缘的得尔布干成矿带.该矿床赋存于上侏罗统满克头鄂博组酸性火山岩中,受NW向断裂构造控制,主矿体呈脉状产出.由于缺少适合传统放射性同位素定年的矿物,其成矿时代未得到很好的限定,制约了对矿床成因的认识.本文采用矿床中与矿石矿物密切共生的黄铁矿Re-Os同位素定年技术对比利亚谷...  相似文献   

Detection of gravitational waves from astrophysical sources     

V. B. Braginsky 《Astronomy Letters》2008,34(8):558-562

Modern ground-based gravitational-wave antennas designed to detect bursts of gravitational radiation from astrophysical catastrophes are described. Basic antenna characteristics, peculiarities of the noise background in antennas from various sources, and methods of their suppression are presented. The contribution from cosmic rays to the background is estimated. New programs of searching for low-frequency gravitational waves and potentialities for increasing the sensitivity of antennas of new types are briefly described.  相似文献   

Visualizing aerial wildlife movements: Internet sources of Doppler radar for the classroom     

Emariana S. Taylor  David R. Butler 《国际地球制图》2013,28(4):247-258

Doppler radar imagery is a useful classroom tool for studying the movement and spatio-temporal distribution of animals. In this paper we present a basic introduction to Doppler radar and the base products used to garner biological and geographical data. We draw upon imagery depicting bat and avian movements to illustrate how radar imagery may be beneficially used in the classroom to examine habitat use and species distribution at the landscape scale. Additionally we provide references for data acquisition and real-time animated imagery available on the Internet. We hope the information and imagery provided here will help instructors enrich the classroom experience for their students, while at the same time demonstrating real-world applications for the use of radar imagery in biogeographic studies.  相似文献   

Identifying the origin of groundwater for water resources sustainable management in an arid oasis,China     

Xiaoyan Guo  Jianhua Si  Yongping Wei  Ting Bao  Haiyang Xi 《水文科学杂志》2013,58(10):1253-1264

ABSTRACT

Many oases are experiencing severe groundwater depletion due to increased population, expanding agriculture and economic development. For sustainable development, quantifying groundwater recharge resources are fundamentally important. In this study, stable isotope techniques were employed to identify recharge sources of groundwater and quantitatively evaluate their contribution ratios in the Dunhuang Oasis, northwest China. Our findings indicate that heavy isotopes in shallow groundwater are more negative than those in deep groundwater, which is attributed to shallow groundwater that was modern and deep groundwater that was old. Irrigated return water and lateral groundwater flow from the Qilian Mountains are considered as the two main sources of shallow groundwater, accounting for 35% and 65% of the total recharge, respectively. Thus, as the main groundwater source of the Dunhuang Oasis, the Qilian Mountain Front should be protected against over-exploitation. Our results provide not only fundamental knowledge for groundwater management of aquifers of the Oasis, but also valuable water management information for other similar arid oases worldwide.  相似文献   

Interannual variation of suspended sediment load and sediment yield in an alpine catchment     

《水文科学杂志》2013,58(6):899-915

Abstract

The results are described of 16 years operation of a measuring station for the automatic recording of water discharge, bed load and suspended sediment transport in the Rio Cordon catchment, a small alpine basin (5 km²) located in northeastern Italy. Hillslope erosion processes were investigated by surveying individual sediment sources repeatedly. Annual and seasonal variations of suspended sediment load during the period 1986–2001 are analysed along with their contribution to the total sediment yield. The results show that suspended load accounted for 76% of total load and that most of the suspended sediment transport occurred during two flood events: an extreme summer flash flood in September 1994 (27% of the 16-years total suspended load) and a snowmelt-induced event in May 2001 accompanied by a mud flow which fed the stream with sediments. The role of active sediment source areas is discussed in relation to the changes in flood peak—suspended load trends which became apparent after both the 1994 and the 2001 events.  相似文献