Geological characteristics and ore genesis of Houfangzi graphite deposit in Northwestern Hebei Province     

ZHANG Xingkang  FAN Yupeng  JIN Song  JIA Zhenghai 《中国地质调查》2021,7(6):20-26

Houfangzi graphite deposit is located in the middle of the graphite metallogenic belt in the northern margin of North China Block in Hebei Province, which belongs to regional metamorphic type graphite deposit. In this paper, through rock-mineral determination, IP ladder sections and exploratory trench survey, the authors have discussed its metallogenic geological characteristics and ore body characteristics, and analyzed its ore genesis. The research results show that the ore bodies are mainly in the graphitic marble of Dongjingzi Formation of Hongqiyingzi Group, which are stratified and controlled by layers, with NE trend and NNW inclination. The IP anomaly shows that Houfangzi graphite deposit is characterized by low resistance and high polarization. Ore bodies are stable and of big scale, and their fixed carbon content ranges from 1.42% to 3.28%, which has the potential to be a large graphite deposit. The ore-forming material came from granulite and graphite marble, while the regional metamorphism is the main mineralization of Houfangzi graphite deposit, with the enrichment and increasement caused by late magmatic activity and migmatization.  相似文献   

Petrogenesis and sedimentary environment of silicate in Late Paleozoic in Kala area of Western Sichuan Province     

LIU Daming  YAO Hongyou  HU Lin  YU Liang  LIU Yizhong 《中国地质调查》2021,7(6):68-78

In order to study the sedimentary environment characteristics of the Late Paleozoic in Kala area of Western Sichuan Province, the authors have conducted the petrological and geochemical analyses of the widely distributed silicate in Qiongyi Formation of Lower Carboniferous and Kawenggou Formation of Upper Permian. The results show that the silicate in the study area belongs to the pure siliceous rocks, with a continuous supply of land-based materials during the deposition process. The average Al/(Al+Fe+Mn) ratio is 0.62, and the silicate shows a biogenic origin by the Al-Fe-Mn diagram. The ratios of Al₂O₃/ (Al₂O₃+ Fe₂O₃), Th/U, Th/Sc, (La/Ce)_N and (La/Yb)_N and tectonic environment discriminant diagram demonstrate that the silicate developed in a shallow-slope depesitional environment in the continental margin. The Ce_anom value is -0.04 to 0.07, and it gradually increases from the Carboniferous to the Permian period, indicating the water body is in an anoxic environment with gradually increasing reducibility. The Garz--Litang basin opened in the Carboniferous period, in accordance with the regional geological evolution, and it continued to expand during the Permian period, with the gradually increasing depth of the seawater within the sedimentary basins.  相似文献   

Rhyolites in continental mafic Large Igneous Provinces: Petrology,geochemistry and petrogenesis     

Mahesh Halder  Debajyoti Paul  Sarajit Sensarma 《地学前缘(英文版)》2021,12(1):53-80

We present a detailed review of the petrological and geochemical aspects of rhyolite and associated silicic volcanic rocks(up to 20 vol%of all rocks)reported to date from twelve well known Phanerozoic continental mafic Large Igneous Provinces(LIPs).These typically spread over<104 km^2(rarely 105 km^2 for Parana-Etendeka)area and comprise<10~4 km^3 of extrusive silicic rocks,erupted either during or after the main basaltic eruption within<5 Myr,with some eruption(s)continuing for≤30 Myr.These rhyolites and associated silicic volcanic rocks(60-81 wt.%of SiO2)are mostly metaluminous to peraluminous and are formed via(ⅰ)fractional crystallization of parental mafic magma with negligible crustal contamination,and(ⅱ)melting of continental crust or assimilation and fractional crystallization(AFC)of mafic magma with significant crustal contribution.Rhyolites formed by extensive fractional crystallization are characterized by the presence of clinopyroxene phenocrysts,exhibit steep negative slopes in bivariate major oxides plots and weak to no Nb-Ta anomaly;these typically have temperature>900℃.Rhyolites formed by significant crustal contribution are characterized by strong negative Nb-Ta anomalies,absence of clinopyroxene phenocrysts,and are likely to have a magma temperature<900℃.Geochemical signatures suggest rhyolite melt generation in the plagioclase stability field with a minor fraction originating from lower crustal depths.A large part of the compositional variability in rhyolites,particularly the SrNd-Pb-O isotope ratios,suggests a significant role of continental crust(upper crustal melting or AFC)in the evolution of these silicic rocks in the continental mafic LIPs.  相似文献   

Migration and speciation transformation mechanisms of mercury in undercurrent zones of the Tongguan gold mining area,Shaanxi Loess Plateau and impact on the environment     

《China Geology》2021,4(2):311-328

In order to study the migration and transformation mechanism of Hg content and occurrence form in subsurface flow zone of gold mining area in Loess Plateau and its influence on water environment, the field in-situ infiltration test and laboratory test were carried out in three typical sections of river-side loess, alluvial and proluvial strata in Tongguan gold mining area of Shaanxi Province, and the following results were obtained: (1) The source of Hg in subsurface flow zone is mainly caused by mineral processing activities; (2) the subsurface flow zone in the study area is in alkaline environment, and the residual state, iron and manganese oxidation state, strong organic state and humic acid state of mercury in loess are equally divided in dry and oxidizing environment; mercury in river alluvial or diluvial strata is mainly concentrated in silt, tailings and clayey silt soil layer, and mercury has certain stability, and the form of mercury in loess is easier to transform than the other two media; (3) under the flooding condition, most of mercury is trapped in the silt layer in the undercurrent zone where the sand and silt layers alternate with each other and the river water and groundwater are disjointed, and the migration capacity of mercury is far less than that of loess layer and alluvial layer with close hydraulic connection; (4) infiltration at the flood level accelerates the migration of pollutants to the ground; (5) the soil in the undercurrent zone is overloaded and has seriously exceeded the standard. Although the groundwater monitoring results are safe this time, relevant enterprises or departments should continue to pay attention to improving the gold extraction process, especially vigorously rectify the small workshops for illegal gold extraction and the substandard discharge of the three wastes, and intensify efforts to solve the geological environmental problems of mines left over from history. At present, the occurrence form of mercury in the undercurrent zone is relatively stable, but the water and soil layers have been polluted. The risk of disjointed groundwater pollution can not be ignored while giving priority to the treatment of loess and river alluvial landform areas with close hydraulic links. The research results will provide a scientific basis for water conservancy departments to groundwater prevention and control in water-deficient areas of the Loess Plateau.  相似文献   

降水对江浙沪PM_(2.5)的清除效率研究     

范凡  陆尔  葛宝珠  王自发 《气象科学》2019,39(2):178-186

为了解不同程度的降水对江浙沪地区大气PM_(2.5)的清除作用,搜集了2014—2016年该地区41个城市的降水和PM_(2.5)观测数据,通过对比2 a非降水和全时段PM_(2.5)平均浓度的差异,发现前者显著高于后者,说明降水对该地区PM_(2.5)具有清除作用。利用降水前与降水期间PM_(2.5)的浓度差异作为降水对PM_(2.5)的清除率,降水后与降水期间的浓度差异作为雨后浓度回升的增加率,分别研究了目标区域不同时期、不同降雨量以及不同降雨时长对PM_(2.5)的清除效果。结果显示:(1)与江浙沪南部地区不同的是,北部地区降水清除率与降水前浓度存在正相关,降水后浓度的增加与当地的排放量呈正相关。(2)当降水量为30 mm或者降水时长为36 h时,清除率增幅减缓,说明降水对PM_(2.5)的清除效率存在着阈值。  相似文献   

CMIP5多模式集合对江苏省气候变化模拟评估及情景预估     

赵亮  刘健  靳春寒 《气象科学》2019,39(6):739-746

利用中国气象局所属的2 400余个台站观测资料制作的分辨率为0.25°×0.25°数据集中的气温、降水量资料评估了CMIP5中17个模式对于1961—2004年江苏省气温和降水量空间分布特征的模拟能力,筛选出了5个对江苏省气候特征模拟较好的模式。之后基于5个优选模式集合平均的结果预估了3种典型浓度路径(Representative Concentration Pathways,RCPs)下江苏省2006—2100年的气温和降水量变化趋势。结果表明:(1)全球耦合气候模式对江苏省的气温和降水量空间分布特征具有一定的模拟能力,并且模式集合平均的气温和降水量与观测资料的空间相关系数分别为0.85和0.93;(2)在低浓度路径(RCP2.6)、中浓度路径(RCP4.5)和高浓度路径(RCP8.5)3种温室气体排放情景下,江苏省2006—2100年的地表温度均呈现明显的增温趋势,并且苏北的增温幅度要高于苏南;(3)3种温室气体排放情景下,江苏省未来百年降水量均呈现出北方增多南方减少的趋势;(4)未来百年江苏省降水量随气温变化的趋势并不稳定,RCP2.6和RCP4.5情景下降水量随气温的升高而增加,而RCP8.5情景下降水量随气温的增加而减少。  相似文献   

四川省旅游气候舒适度评价          下载免费PDF全文

严霜  董廷旭  杜华明  林孝先 《高原山地气象研究》2019,39(1):74-80,86

为了更好地发展旅游事业,本文以四川省2006~2016年21个站点的气象数据为基础数据,运用奥利弗温湿指数和IDW空间插值法对四川省旅游气候舒适度进行评价。结果表明:(1)从总体上看,四川省旅游气候舒适度差异显著,呈现出西部较高、东部较低的特征;(2)从季节上看,四川省春、秋季舒适度较高,最适合人们旅游;夏、冬季舒适度较差,最不适合旅游;(3)从旅游地上看,除了甘孜州、阿坝州和凉山州的最舒适时期为7月,最不舒适时期为1月。四川省典型旅游地最舒适时期大都为4月和10月,最不舒适时期主要为1月和7月。因此,除甘孜州,阿坝州和凉山州外,4月和10月四川省适合旅游;相反,1月和7月四川省不适合旅游。  相似文献   

山东省沂水县农村非农化程度差异及驱动力   总被引：7，自引：1，他引：6  

张佰林  张凤荣  曲宝德  李灿  陈军伟 《地理学报》2015,70(6)

非农化是中国快速工业化、城镇化进程中农村演变的重要趋势,呈现出明显的空间异质性。以山东省沂水县为例,选取16个典型样点村,根据农户就业地域空间差异,将农户就业划分为县域外非农就业、县域非农就业、县域非农兼业和农业生产4类,在此基础上,选取非农就业劳动力、收入和时间比例3个指标研究县域农村非农化程度差异及驱动力。结果表明,沂水县农村非农化程度介于37.54%~90.65%,非农化现象普遍。县域农村非农化程度的总体分布特征为:近郊村最高;随着与城镇的临近,粮食作物主导村提高、经济作物主导村降低;同一地形区内,粮食作物主导村高于经济作物主导村。农村非农分化趋势明显。驱动力研究表明,受县域城镇经济实力、农村到城镇的可达性,农业收益及劳动需求量等的综合影响,不同类型农村劳动力就业结构存在差异,进而导致县域农村非农化程度的差异。研究认为,当前农村非农化普遍,且非农分化明显。政府应根据不同类型农村非农化程度差异的内容及驱动因素,实施差别化的农村发展管理措施。  相似文献   

甘肃省稀有金属矿产特征与成矿规律初探   总被引：1，自引：0，他引：1  

周会武  李通国  张有奎  余君鹏  朱文戈  刘养雄  张红斌 《矿床地质》2015,34(5):1030-1045

通过20世纪六七十年代和2010年至今2个主要勘查阶段的工作,甘肃省境内共发现了51处稀有金属矿床和矿(化)点,主要成矿类型为碱性花岗岩型和花岗伟晶岩型,其次有变粒岩型、云英岩型和变中酸性火山岩型等。这些矿床和矿(化)点主要分布在北山地区,其次为龙首山、阿尔金山和西秦岭地区,大部分产出于古老地块边缘的火山、岩浆及构造活动带。矿体的产出受岩浆岩侵入体或断裂构造控制,新太古界—古元古界变质地层是主要的赋矿围岩地层,矿体主要产出于华力西中-晚期侵入的花岗岩和伟晶岩中,成矿时代主要为石炭纪—二叠纪,其次为志留纪、三叠纪、奥陶纪、第四纪、侏罗纪。  相似文献   

安徽铜陵胡村南铜钼矿床流体成矿过程   总被引：1，自引：0，他引：1  

郑泽军  杜杨松  鲁颖淮  陈林杰  杨赫鸣  张芸  任春雷  江勇卫 《矿床地质》2015,34(4):692-710

胡村南铜钼矿床是在安徽铜陵铜(金)矿集区中发现的第一个矽卡岩-斑岩复合型铜钼矿床,在长江中下游成矿带具有特殊性和典型性。文章对该矿床进行了矿床地质和流体包裹体研究,旨在查明该矿床的流体成矿过程。胡村南铜钼矿床流体成矿过程可以划分为高温气成热液期、中高温热液期和低温热液期3个成矿期。高温气成热液期发育钾长石化和矽卡岩化,中高温热液期发育绿泥石化、绿帘石化和绢云母化,而低温热液期主要发育碳酸盐化。其中,中高温热液期为主要矿化期,形成辉钼矿和黄铜矿等多种硫化物网脉。高温气成热液期矿物中发育富液相和含子晶多相包裹体,中高温热液期矿物中也主要发育富液相包裹体和含子晶多相包裹体,但可见少量的富气相包裹体,低温热液期矿物中只发育富液相包裹体。从高温气成热液期经中高温热液期到低温热液期,成矿流体均一温度从435℃以上,经203~458℃,降低到156~276℃;盐度w(NaCleq)从14.0%~64.9%,经4.6%~47.5%,降低到1.0%~15.5%。成矿流体在其演化过程中发生过不混溶作用和沸腾作用。不混溶作用发生在气成热液期,使成矿流体中的成矿元素大量富集。沸腾作用发生在中高温热液期,导致成矿流体中的成矿元素卸载而沉淀出大量金属硫化物。  相似文献