甘肃小柳沟钨多金属矿地质特征及成矿模式   总被引：12，自引：1，他引：12       下载免费PDF全文

安涛  周继强 《甘肃地质》2002,11(2):54-66

小柳沟钨多金属矿于 90年代初发现 ,目前已具大型、超大型规模。共有 4个矿床。成矿主要与长城系朱龙关群和隐伏花岗岩有关。该矿床成矿物质来源具双重性 ,成矿温度为中高温 ,成矿流体为中等盐度 ,同位素计算模式年龄确定其成矿于加里东期。矿床成因属于火山喷发沉积—岩浆热液改造矿床。  相似文献   

中条山西南段与变基性岩有关的铜矿地质特征及成因浅析     

薛克勤  赵月凤  董清雷 《华北地质》2002,(Z1)

与变基性岩有关的铜矿 ,是在中条山西南段新发现的一种新的铜矿类型 ,其形成是在原始基性岩浆侵入或喷发作用形成的矿源岩或矿化体基础上 ,经过区域变质和印支 -燕山期构造 -岩浆热液的改造加富而成 ,其成因应属与变基性岩有关的变质 -热液改造型铜 (镍、铁 )矿床。  相似文献   

华北陆块北缘西段中元古代与裂谷作用有关的铁、稀土、多金属矿床特征及成因     

曹秀兰 《华北地质》2002,(Z1)

华北陆块北缘西段狼山—白云鄂博裂谷系中元古代形成的大型多金属矿床 ,是我国重要的铁、稀土、铜、铅、锌矿产地。矿床为产于沉积岩中热水沉积型多金属矿床。其形成受地层、构造控制 ,与裂谷作用有着密切的关系。裂谷系内外分支的地质环境及矿床矿种不同 ,导致矿床特征及成因具有一定差异。白云鄂博铁、稀土矿床为钾、钠、磷等含量较高的热水沉积型 ,霍各乞铜、铅、锌多金属矿床为与中基性火山岩有关的过渡热水沉积型 ,东升庙和甲生盘等铅、锌多金属矿床为热水沉积型。文中将对上述矿床分别进行论述。  相似文献   

Sulfur Content and Isotopic Ratio of Cambro-Ordovician Carbonate Rocks from South Korea: A Possible Source for Mesozoic Magmatic-hydrothermal Ore Sulfur     

Shunso ISHIHARA  Myung–Shik JIN  Yoshimichi KAJIWARA 《Resource Geology》2002,52(1):41-48

Abstract: Carbonate rocks of Cambrian (18 samples) and lower-middle Ordovician (11 samples) ages from South Korea were analyzed for sulfur contents of structurally substituted sulfate (SSS) and sulfides and their δ³⁴S values. The δ³⁴S values of SSS ranging from +25.9 to +45.2 permil, are averaged as +33.6 and +33.5 permil for the Cambrian and Ordovician rocks, respectively, which indicate high δ³⁴S values of the Cambro-Ordovician seawater. The SSS contents in the carbonate rocks are low being 2.9 to 17.3 ppm S (averaged as 7.0 ppm S). Sulfide sulfur, on the contrary, is much abundant containing 3 to 1,880 ppm S and the δ³⁴S values range widely between –17.6 and +31.1 permil. Sulfide sulfur of the studied rocks excluding impure carbonates has an average content of 187 ppm S and δ³⁴S value of +12.8 permil (n=24). The estimated δ³⁴S (sulfate–sulfide) values, which range from 13.8 to 25.4 permil in general with a few exceptions from 36.5 up to 52.3 permil for some impure carbonates, may provide evidence for the persistent oceanic anoxia with its temporary recovery during the Cambro-Ordovician time.
The SSS and sulfide sulfurs have often higher δ³⁴S values than the Mesozoic-Cenozoic ore sulfur (Ishihara et al., 2000). Since carbonate rocks are very reactive with circulating hydrothermal ore solution, high δ³⁴S values of the Korean ore deposits might be caused to some extent by ³⁴S enrichment from the host carbonates, resulting in the low SSS contents observed.  相似文献   

Paleomagnetic dating of Alleghanian orogenesis and mineralisation in the Mascot–Jefferson City zinc district of East Tennessee, USA     

D. T. A. Symons  K. K. Stratakos 《Tectonophysics》2002,348(1-3)

The Mascot–Jefferson City (M-JC) Mississippi Valley-type (MVT) deposits are in the Valley and Ridge province of the Appalachian orogen in East Tennessee. They have been a major source of zinc for the USA but their age is uncertain and thus their genesis controversial. About 10 specimens from each of 37 sites have been analysed paleomagnetically using alternating field and thermal step demagnetisation methods and saturation isothermal remanence methods. The sites sample limestones, dolostones, breccia clasts and sphalerite–dolomite MVT mineralisation from mines in the Lower Ordovician Kingsport and Mascot formations of the Knox Group. The characteristic remanent magnetisation (ChRM) is carried by magnetite in the limestones, by both magnetite and pyrrhotite in the dolostones and by pyrrhotite preferentially to magnetite in the mineralisation. Mineralized sites have a more intense ChRM than non-mineralised, indicating that the mineralising and magnetisation event are coeval. Paleomagnetic breccia tests on clasts at the three sites are negative, indicating that their ChRM is post-depositional remagnetisation, and a paleomagnetic fold test is negative, indicating that the ChRM is a remagnetisation, and a post-dates peak Alleghanian deformation. The unit mean ChRM direction for the: (a) limestones gives a paleopole at 129°E, 12°N (d_p=18°, d_m=26°, N=3), indicating diagenesis formed a secondary chemical remanent magnetisation during the Late Ordovician–Early Silurian; (b) dolomitic limestones and dolostone host rocks gives a paleopole at 125.3°E, 31.9°N (d_p=5.3°, d_m=9.4°, N=7), recording regional dolomitisation at 334±14 Ma (1σ); and (c) MVT mineralisation gives a paleopole at 128.7°E, 34.0°N (d_p=2.4°, d_m=4.4°, N=25), showing that it acquired its primary chemical remanence at 316±8 Ma (1σ). The mineralisation is interpreted to have formed from hydrothermal fluid flow, either gravity or tectonically driven, after peak Alleghanian deformation in eastern Tennessee with regional dolomitisation of the host rocks occurring as part of a continuum during the 20 Ma prior to and during peak deformation.  相似文献   

数字地震仪的发展历史及展望   总被引：4，自引：4，他引：4  

朱铉 《地球物理学进展》2002,17(2):301-304

地震仪经历了光点，模拟和数字的变化，数字地震仪本身由16位发展到24位，其附属设备（电缆，检波器）也是到了不同程度的发展。近年来，I／O等公司利用MEMS技术研制了新型地震检波器，这一新的发展对于地震采集尤其是多分量采集带来重要影响。  相似文献   

Alpine medicinal plant trade and Himalayan mountain livelihood strategies   总被引：5，自引：0，他引：5  

Carsten Smith Olsen  Helle Overgaard Larsen 《The Geographical journal》2003,169(3):243-254

Commercial alpine medicinal plants are collected from the wild by local rural households throughout the Himalaya and sold in order to increase household incomes. Recent studies indicate that this annual trade amounts to thousands of tonnes of roots, rhizomes, tubers, leaves, etc., worth millions of US dollars. The main market is in India. Based on a national survey, including the most commonly traded species, and a village study this paper investigates the importance of the alpine medicinal plant trade at national and local levels in Nepal. The national survey included standardized open-ended interviews with 232 harvesters, 64 local traders, 66 central wholesalers, 47 regional wholesalers, and 16 production companies. The village survey is based on the daily records of household activities in 15 households in a one-year period. The annual Nepalese alpine and sub-alpine medicinal plant trade is conservatively estimated to vary from 480 to 2500 t with a total harvester value of US$0.8–3.3 million; the average harvester value is estimated at US$66.0 ± 99.0. The trade in 1997/98 amounted to 1600 t with a harvester value of US$2.3 million and an export value equivalent to 2.5% of total export from Nepal. Medicinal plant harvesting was found to constitute an integrated part of local livelihood strategies, contributing from 3 to 44% (average of 12%) of the annual household income. Importance at household level depended on land and animal holdings, and the availability of adult male labour. The validity and reliability of methods and analyses is evaluated, and issues of conservation and management of alpine medicinal plant species under the community forestry scheme are discussed.  相似文献   

我国制造业集群分布现状及其发展特征   总被引：28，自引：0，他引：28  

王缉慈 《地域研究与开发》2003,22(6):29-33

目前，在我国很多地区，例如长江三角洲和珠江三角洲，以个别市、县、镇或村为范围，集中某种产品的生产所形成的制造业集群表现出极强的活力和竞争力。集群中的很多企业根据不同技术能力，纷纷进入了全球价值链，已经使中国成为跨国公司控制之下的“世界工厂”。文章从目前局限性的资料出发，将这一现象的分布现状进行了分析，并对其发展特征进行了描述。认为，在新型工业化道路中，企业只有在本地舍作和结网，加强创新，才能有效地插入全球价值链，参与国际竞争。为此，需要通过政策的支持，鼓励合作的信用环境，使价值链上的各级企业以及利益相关者进行合作。  相似文献   

浙江原发性产业集群的形成机制与持续发展   总被引：10，自引：0，他引：10  

李植斌 《地域研究与开发》2003,22(6):34-36,42

原发性产业集群是浙江省产业发展的主要模式，是在开放的环境中自发形成的。独特的区域“文化基因”，产业特定性知识，产业氛围与地方政府的促进作用是原发性产业集群形成的主要因素；小企业大群落，区内企业的分工协作与竞争，产品的多样化与差别化及集体学习是其主要特点；生产要素的培育和创造，区域品牌树立，学习型企业群落创建及特色制造业基地的培育是产业集群区持续发展的主要措施。  相似文献   

Re-placing the Pilbara's mining unions     

Bradon Ellem 《The Australian geographer》2003,34(3):281-296

This paper examines the attempt by mining management in Western Australia's Pilbara to replace mining unions—quite literally—by removing them from the processes of representation and bargaining. It analyses the way in which those unions have tried to re-place themselves, in the senses of transforming themselves in those spaces in which they were already operating and reviving themselves where they were not. Where unionists have succeeded in these engagements, it has been by working at a range of geographical scales, using the ‘power of place’ in the Pilbara and reshaping traditional geographies of union organisation. It is suggested here that many of these emergent outcomes are the result of the embeddedness of geographically specific historical structures along with new intersections of nationally and locally scaled labour politics.  相似文献