大巴山南部房县东河辉绿玢岩LA ICP MS 锆石U Pb测年及其构造意义     

曹亮  张权绪  胡尚军  段其发  周云  于玉帅  邹先武  甘金木 《地质学报》2015,89(12):2314-2322

大巴山构造带位于秦岭造山带和扬子板块的过渡部位,形成于印支-燕山期,定型于喜山期。前人对北大巴山地区基性岩年代学已有研究,但对大巴山南部地区基性岩却很少高精度年龄报道。本文对大巴山南部房县东河地区的辉绿玢岩脉进行LA-ICP-MS锆石U-Pb年龄测定,结果表明,东河辉绿玢岩形成于439.3Ma,相当于早志留世。与北大巴山镇坪地区辉绿岩,紫阳-岚皋地区基性岩及火山岩形成时代基本一致。结合前人的研究结果表明,大巴山南部地区在早志留世处于张裂状态,东河地区的基性岩为岩石圈处于拉张状态下大陆裂谷作用产物。此处439.3Ma的年龄值,也说明此时扬子板块北缘普遍处于拉张的构造环境,代表了在早志留世大巴山南部裂谷盆地的伸展裂陷幅度达到最大。本次研究所获得的年龄数据,确定了围岩竹山组形成不晚于早志留世,限定地层时代为寒武纪-奥陶纪。  相似文献   

Metallogeny and environmental impact of Hg in Zn deposits in China     

Runsheng Yin  Xinbin Feng  Zhonggen Li  Qian Zhang  Xianwu Bi  Guanghui Li  Jinling Liu  Jingjing Zhu  Jianxu Wang 《Applied Geochemistry》2012

Zinc smelting is currently regarded as one of the most important atmospheric Hg emission sources in the world. In order to assess the potential environmental impacts of Hg from Zn smelting in China, the distribution of total Hg concentration (HgT) in Zn concentrates (ZCs) from 100 Zn deposits in China was investigated. It was found that HgT varies depending on the ore types and their geneses. Zinc concentrates from sedimentary-exhalative deposits (SEDEX, geometric mean = 48.2 μg/g) have the highest HgT. The possible explanation is that the sources of mineralizing solutions for SEDEX deposits are deep formational brines in contact with sedimentary rocks, and there are much higher background Hg contents in sedimentary rocks. Zinc concentrates from volcanic hosted massive sulfide deposits (VMS, geometric mean = 11.5 μg/g) and Mississippi Valley-Type (MVT, geometric mean = 10.1 μg/g) deposits have intermediate HgT. VMS may receive most of their Hg from fluid–rock interaction and/or by direct input of gaseous Hg from a mantle source. However, the source of metals within MVTs may be the low-temperature hydrothermal solution formed by diagenetic recrystallization of the carbonates. Intrusion related deposits (IRs) have the lowest HgT (Geomean = 2.4 μg/g), and the dispersion of Hg in the IRs seems to be influenced by the temperature of ore formation and/or the nature of wall–rock alteration. Finally, it was estimated that the annual Hg emission to the atmosphere from Zn smelting in China was about 107.7 tons in 2006.  相似文献   

Geology, geochemistry, geochronology and genesis of the Yangla skarn copper deposit, Yunnan Province, China     

ZHU Jingjing  HU Ruizhong  BI Xianwu  ZHONG Hong  Zhang Xingchun 《《地质学报》英文版》2013,87(Z1):851-852

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A time-dependent stochastic grassland fire ignition probability model for Hulun Buir Grassland of China     

GUO Zhixing  FANG Weihua  TAN Jun  SHI Xianwu 《中国地理科学(英文版)》2013,23(4):445-459

Grassland fire is one of the most important disturbance factors in the natural ecosystems.This paper focuses on the spatial distribution of long-term grassland fire patterns in the Hulun Buir Grassland located in the northeast of Inner Mongolia Autonomous Region in China.The density or ratio of ignition can reflect the relationship between grassland fire and different ignition factors.Based on the relationship between the density or ratio of ignition in different range of each ignition factor and grassland fire events,an ignition probability model was developed by using binary logistic regression function and its overall accuracy averaged up to 81.7%.Meanwhile it was found that daily relative humidity,daily temperature,elevation,vegetation type,distance to county-level road,distance to town are more important determinants of spatial distribution of fire ignitions.Using Monte Carlo method,we developed a time-dependent stochastic ignition probability model based on the distribution of inter-annual daily relative humidity and daily temperature.Through this model,it is possible to estimate the spatial patterns of ignition probability for grassland fire,which will be helpful to the quantitative evaluation of grassland fire risk and its management in the future.  相似文献   

鄂西—湘西地区震旦系灯影期岩相古地理与层控铅锌矿关系初探   总被引：4，自引：0，他引：4  

汤朝阳  段其发  邹先武  李堃 《地质论评》2009,55(5):712-721

依据研究区震旦系十余条代表性剖面的沉积特征及其横向展布规律,并结合两种相变面和两种穿时性划分出的地层格架,应用等时面优势相成图方法编制了震旦系灯影期岩相古地理图。区内古地理格局具有东高西低、北浅南深（水深）的特点,沉积自南西向北东超覆,层位逐渐抬高、穿时;岩性、厚度、颜色和沉积相类型上的差异是统一沉积背景下沉积物相变、穿时的结果。灯影组以发育大套白云岩为特征,纵向上构成总体向上变浅的沉积相序列,同时反映了缓坡型碳酸盐岩台地的生长发育过程;空间上从北西至南东发育从潮坪、局限台地、浅滩、台地边缘斜坡到台地前缘盆地等沉积。岩相古地理对层控铅锌矿具有明显的控制作用,主要分布于台地边缘浅滩相与局限台地潮下过渡部位。  相似文献   

Crystallisation conditions (T, P, fO2) from mineral chemistry of Cu- and Au-mineralised alkaline intrusions in the Red River–Jinshajiang alkaline igneous belt, western Yunnan Province, China     

Bi Xianwu  Hu Ruizhong  J. J. Hanley  J. E. Mungall  Peng Jiantang  Shang Linbo  Wu Kaixing  Suang Yan  Li Hongli  Hu Xiaoyan 《Mineralogy and Petrology》2009,96(1-2):43-58

The Oligocene Yao’an syenite porphyry, associated with gold mineralisation, and the Machangqing alkali granite porphyry–monzonite porphyry, associated with Cu mineralisation, belong to the Red River–Jinshajiang alkaline igneous belt that formed in a continental setting in southwestern China. A study of the mineral chemistry of major silicate minerals in these two mineralised intrusions provides insights into their overall crystallisation conditions. The temperature and pressure conditions, derived from amphibole–plagioclase and perthite–plagioclase geothermometry and Al-in-amphibole barometry, suggest that the Yao’an intrusion crystallised at around 820?±?50°C and 0.9–1.3 kbar, whereas the Machangqing intrusion crystallised at around 730?±?50°C and 2.2–2.8 kbar. The higher temperature and lower pressure of crystallisation for the Yao’an intrusion relative to the Machangqing intrusion indicates that it was emplaced at a shallower crustal level. Based on biotite composition, the two intrusions formed under imposed oxygen fugacities above the Ni–NiO buffer (NNO), and the Yao’an intrusion crystallised under more oxidising conditions than the Machangqing intrusion. The results show that the intrusions associated with Cu–Au mineralisation in the Red River–Jinshajiang alkaline igneous belt were emplaced at a relatively high fO₂, which, together with the weakly fractionated magma, favoured Au enrichment relative to Cu in the belt.  相似文献   

云南大坪金矿床矿化剂来源及其对金成矿的制约   总被引：18，自引：1，他引：17  

毕献武  胡瑞忠 《矿物学报》1999,19(1):28-33

本文基于对大坪金矿成矿流体中矿化剂来源、成矿时代和成矿流体形成演化过程中水－硫化剂－－金耦合作用关系的研究,探讨了大坪金矿床形成的可能机制。研究结果表明,大坪金矿的成矿时代约为５０Ｍａ,金成矿所需的矿化为自深部。大坪金矿床之所以形成在喜山早期,主要是通过喜山早期富矿化剂的深源流体上升,加入原在闪长岩体内循环的贫矿化剂本,从而使这种贫矿化剂的流体转化成富矿化剂进而能够浸取金的成矿流体来实现的。  相似文献   

圆尾斗鱼食物选择性的实验研究   总被引：1，自引：0，他引：1  

郭先武  周洁  杨灵 《湖泊科学》1995,7(2):173-177

在实验条件下,圆尾斗鱼优摄食纹幼虫和摇蚊幼虫,对食物的选择性明显,同时表明,用数量指标,以选择指数和Ｘ＾２检验能较客观地,可靠地说明食物选择性的大小。  相似文献   

Precipitation and temperature trends for the Southwest China: 1960–2007     

Nianxiu Qin  Xi Chen  Guobin Fu  Jianqing Zhai  Xianwu Xue 《水文研究》2010,24(25):3733-3744

Daily temperature and precipitation data from 136 stations of Southwest China (SWC) during the last five decades, from 1960 to 2007, were analysed to determine the spatial and temporal trends by using the Mann–Kendall trend test. Results show that SWC has become warmer over the last five decades, especially in the recent 20–25 years. The increasing trends in winter months are more significant than those in the months of other seasons, and spatially Tibet, Hengduan mountains area and west Sichuan Plateau have larger temperature trend in magnitude than the other regions have. A downward trend was detected in Sichuan Basin also, but the region with cooler temperature was shrinking due to the statistically significant increasing trend of temperature after 1990s. Both annual and seasonal means of daily maximum and minimum temperatures show an increasing trend, but trend magnitude of minimum temperature was larger than that of maximum temperature, resulting in the decrease of diurnal temperature range for SWC in the last 50 years. Annual precipitation showed slightly and statistically insignificant increasing trend, but statistically significant increasing trend has been detected in winter season while autumn witnessed a statistically significant decreasing trend. The results could be a reference for the planning and management of water resources under climate change. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Infrared microthermometric and stable isotopic study of fluid inclusions in wolframite at the Xihuashan tungsten deposit,Jiangxi province,China   总被引：7，自引：0，他引：7  

Wenfeng?Wei  Ruizhong?HuEmail author  Xianwu?Bi  Jiantang?Peng  Wenchao?Su  Shengqiong?Song  Shaohua?Shi 《Mineralium Deposita》2012,47(6):589-605

The Xihuashan tungsten deposit, Jiangxi province, China, is a world-class vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. There are two major sets of subparallel ore-bearing quartz veins. The ore mineral assemblage includes wolframite and molybdenite, with minor amounts of arsenopyrite, chalcopyrite, and pyrite. There are only two-phase aqueous-rich inclusions in wolframite but at least three major types of inclusions in quartz: two- or three-phase CO₂-rich inclusions, two-phase pure CO₂ inclusions and two-phase aqueous inclusions, indicating boiling. Fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities (239–380°C, 3.8–13.7 wt.% NaCl equiv) compared with those in quartz (177–329°C, 0.9–8.1 wt.% NaCl equiv). These distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process. Enthalpy–salinity plot shows a linear relationship, implying mixing of different sources of fluids. Although boiling occurred during vein-type mineralization, it seems negligible for wolframite deposition. Mixing is the dominant mechanism of wolframite precipitation in Xihuashan. δ³⁴S values of the sulfides range from −1.6 to +0.1‰, indicative of a magmatic source of sulfur. δ¹⁸O values of wolframite are relatively homogeneous, ranging from +4.8‰ to +6.3‰. Oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite.  相似文献