Petrogenesis and significance of early Yanshanian syenite-granite complex in eastern Nanling Range   总被引：4，自引：2，他引：4  

CHEN Peirong  ZHOU Xinmin  ZHANG Wenlan  LI Huimin  FAN Chunfang  SUN Tao  CHEN Weifeng & ZHANG Min . State Key Laboratory of Mineral Deposits Research  Department of Earth Sciences  Nanjing University  Nanjing  China  . Tianjin Institute of Geology  Mineral Resources  China Geological Survey  Tianjin  China 《中国科学D辑(英文版)》2005,48(7)

According to the statistics for granitoid distribution map of 1/2000000 Nanling region[1], the granitoids in the Nanling region sum up an area of more than 170000 km2, occupying about one fifth of the entire Nanling region. Granitoid rocks in the Nanlingregion are mainly composed of monzogranites (occu- pying more than 84%), granodiorites (about 11%) and syenogranites (about 3%)[2]. There also exists a small amount of syenites (0.12%) with a sum area of about 94 km2[2]. However, nearly half …  相似文献   

北祁连山寒山金矿成矿时代讨论   总被引：6，自引：1，他引：6  

宋忠宝  任有祥  李智佩  杨建国  栗亚芝 《地质与勘探》2005,41(3):12-15

寒山大型金矿是近年来在北祁连山西段发现的与基性火山岩有关的构造蚀变岩型金矿.作者利用Rb-Sr同位素方法测得寒山金矿的成矿时代为339 Ma,属华力西期.指出寒山金矿的成矿时代应为(303～339)Ma,有多期热液叠加,多期成矿作用.因此,作者认为寒山金矿的热液很可能是青山斜长花岗岩(370±25Ma)、寒山辉长岩(347.1±6.4Ma)共同提供的.由于该区有较多的中酸性岩体存在,现成矿时代的确定对于该区在寻找华力西期-加里东晚期蚀变岩型金矿具有重要意义.  相似文献   

宁夏六盘山地区臭水泉群的地质成因及其环境危害分析     

王永  张鹏川 《地质灾害与环境保护》2005,16(2):155-160

六盘山地区多处有臭水泉群出露。臭水泉就是含有Na2SO4、NaCl等盐类矿物离子，并排放硫化氢(H2S)气体的高矿化度咸苦水。在系统分析以往地质资料的基础上，借助ETM卫星图像，提取臭水泉群的分布信息，通过野外实地调查、访问、取样化验，初步查明臭水泉的位置、流量、水质及其对环境的危害，结合地层岩性、地质构造特点，分析臭水泉的地质成因。分析结果表明，六盘山地区的臭水泉主要分布于马东山复背斜的南北两端及东西两翼，以上升泉的形式出露于沟底，中、新生代高含盐量地层是臭水泉群中盐分的物质来源，北东向、北东东向、近南北向断裂和构造裂隙是臭水溢出的通道。臭水泉对环境的危害主要表现在：造成局部大气质量下降，污染地表水体和河谷潜水，造成土壤盐  相似文献   

Radiolarian Age of Chert-hosted Bedded Manganese Deposits from the Gen-otani Mine in the Tamba District, Northern Kyoto City, Japan     

Satoshi Nakae  Kosei Komuro 《Resource Geology》2005,55(4):311-320

Abstract. Numerous bedded manganese deposits sporadically distributed throughout the Tamba district, southwestern Japan are intercalated within chert sequence. It is well known that radiolarian remains are commonly included in both bedded manganese deposits and host cherts. The Gen‐otani mine, one of these deposits, is located at Otani, Keihoku‐Shimonaka, northern Kyoto City. Chemical composition and age of the chert sequence at the mine were examined. Mainly according to SiO₂ and MnO contents together with lithology, the chert sequence is divided into three sections; lower massive chert, middle bedded manganese deposit and upper bedded chert sections. Radiolarian faunas consisting of middle Jurassic species such as Eucyrtidiellum unumaense, Dictyomitrella(?) kamoensis, Parvicingula dhimenaensis, Sethocapsa aitai, Sethocapsa kodrai, Transhsuum brevicostatum, Tricolocapsa plicarum, Unuma echinatus and others were extracted from both the middle manganese section and overlying bedded chert of the upper section. This examination reveals that the bedded manganese deposit at the Gen‐otani mine formed until Bajocian to early Bathonian (middle Middle Jurassic) in age.  相似文献   

The 1998 Hida Mountain, Central Honshu, Japan, earthquake swarm: Double-difference event relocation, frequency–magnitude distribution and Coulomb stress changes     

Bogdan Enescu  Kiyoshi Ito   《Tectonophysics》2005,409(1-4):147-157

By using the double-difference relocation technique, we have determined the fine structure of seismicity during the 1998 Hida Mountain earthquake swarm. The distribution of seismic activity defines two main directions (N–S and E–W) that probably correspond to the regional stress pattern. The detailed structure of seismicity reveals intense spatio-temporal clustering and earthquake lineations. Each cluster of events contains a mainshock and subsequent aftershock activity that decays according to the Omori law. The seismicity and the b-value temporal and spatial patterns reflect the evolution of the static stress changes during the earthquake swarm. About 80% of the swarm's best-relocated events occur in regions of increased ΔCFF. The smaller value of b found in the northern part of the swarm region and a larger b-value observed to the south, for the same period of time, could be well explained by the static stress changes caused by the larger events of the sequence. We argue that the state of stress in the crust is the main factor that controls the variation of b-value.  相似文献   

Geochemical and C, O, Sr, and U-series isotopic evidence for the meteoric origin of calcrete at Solitario Wash, Crater Flat, Nevada, USA     

L. A. Neymark  J. B. Paces  B. D. Marshall  Z. E. Peterman  J. F. Whelan 《Environmental Geology》2005,48(4-5):450-465

Calcite-rich soils (calcrete) in alluvium and colluvium at Solitario Wash, Crater Flat, Nevada, USA, contain pedogenic calcite and opaline silica similar to soils present elsewhere in the semi-arid southwestern United States. Nevertheless, a ground-water discharge origin for the Solitario Wash soil deposits was proposed in a series of publications proposing elevation-dependent variations of carbon and oxygen isotopes in calcrete samples. Discharge of ground water in the past would raise the possibility of future flooding in the unsaturated zone at Yucca Mountain, Nevada, site of a proposed high-level nuclear waste repository. New geochemical and carbon, oxygen, strontium, and uranium-series isotopic data disprove the presence of systematic elevation-isotopic composition relations, which are the main justification given for a proposed ground-water discharge origin of the calcrete deposits at Solitario Wash. Values of δ¹³C (−4.1 to −7.8 per mil [‰]), δ¹⁸O (23.8–17.2‰), ⁸⁷Sr/⁸⁶Sr (0.71270–0.71146), and initial ²³⁴U/²³⁸U activity ratios of about 1.6 in the new calcrete samples are within ranges previously observed in pedogenic carbonate deposits at Yucca Mountain and are incompatible with a ground-water origin for the calcrete. Variations in carbon and oxygen isotopes in Solitario Wash calcrete likely are caused by pedogenic deposition from meteoric water under varying Quaternary climatic conditions over hundreds of thousands of years.  相似文献   

Sedimentary-volcanic tufts formed during the early Middle Triassic volcanic event in Guizhou Province and their stratigraphic significance     

XIAO Jiafei 《中国地球化学学报》2005,24(4):338-344

The sedimentary-volcanic tuff （locally called ＂green-bean rock＂） formed during the early Middle Triassic volcanic event in Guizhou Province is characterized as being thin, stable, widespread, short in forming time and predominantly green in color. The green-bean rock is a perfect indicator for stratigraphic division. Its petrographic and geochemical features are unique, and it is composed mainly of glassy fragments and subordinately of crystal fragments and volcanic ash balls. Analysis of the major and trace elements and rare-earth elements （ REE）, as well as the related diagrams, permits us to believe that the green-bean rock is acidic volcanic material of the calc-alkaline series formed in the Indosinian orogenic belt on the Sino-Vietnam border, which was atmospherically transported to the tectonically stable areas and then deposited as sedimentary-volcanic rocks there. According to the age of green-bean rock, it is deduced that the boundary age of the Middle-Lower Triassic overlain by the sedimentary-volcanic tuff is about 247 Ma.  相似文献   

浙江黄岩富山山崩地貌景观及其旅游开发     

林智理 《热带地理》2005,25(3):268-272

浙江黄岩富山地区受新构造运动的影响，经历了节理发育、流水切割与节理扩张，最终发育成山崩地貌景观。该景观资源丰富，具有组合好、规模大、分布广、科考价值高等特点，是迄今发现的华东地区规模最大的山崩地区。根据《旅游资源分类、调查与评价》的国家标准，对该类景观资源单体进行评价与分级以及开发条件分析，认为黄岩富山山崩地貌观资源具有很大的旅游开发价值。旅游开发时应以保护山崩地质遗迹为前提，以凸显山崩地貌景观的主题与特色为关键，以环境的安全性为根本，实施综合开发。  相似文献   

中国福建省亚热带山地4000年来植被变化的孢粉记录(英文)     

邱宏烈 《福建地理》2006,(3)

根据采自福建省中部戴云山脉亚高山水系源头地带(大致25°40′N,118°11′E)泥炭沉积洼地的孢粉纪录,对该地区亚热带山地植被近4000年来的变化进行了研究.孢粉记录和其他沉积资料显示,3个取样点的泥炭沉积开始于4000年前,很可能是全新世后期气候转冷的结果.在距今4000~1200年前期间,戴云山脉上部(海拔1300~1600m)的植被为亚热带针阔叶混交类型,优势种属包括Cryptomeria(柳杉)、Castanopsis(栲)、Quercus(栎)和Tsuga(铁杉)等.距今1200年前左右,该区域的植被发生了一次大的变化,表现在上述优势属种的孢粉在样品总孢粉数的比例突然下降,而Pinus(松),Gramineae(禾本科)以及Dicranopteris(芒萁)等属种的比例则提高了.这次剧烈的植被变化在其中的一个泥炭钻孔中留下了一层粘土记录,它代表了当时流域内植被受破坏后出现的严重土壤侵蚀.从泥炭沉积提取的孢粉记录还可以看出,研究区内广泛分布的松林是一种次生植被,它是人类不断干扰的结果.  相似文献   

Moho depth and three-dimensional P and S structure of the crust and uppermost mantle in the Eastern Mediterranean and Middle East derived from tomographic inversion of local ISC data   总被引：1，自引：0，他引：1  

Ivan Koulakov  Stephan V. Sobolev 《Geophysical Journal International》2006,164(1):218-235

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