Geology and mineralization of the Sanshandao supergiant gold deposit (1200 t) in the Jiaodong Peninsula,China: A review     

《China Geology》2021,4(4):686-719

The Jiaodong Peninsula in Shandong Province, China is the world’s third-largest gold metallogenic area, with cumulative proven gold resources exceeding 5000 t. Over the past few years, breakthroughs have been made in deep prospecting at a depth of 500–2000 m, particularly in the Sanshandao area where a huge deep gold orebody was identified. Based on previous studies and the latest prospecting progress achieved by the project team of this study, the following results are summarized. (1) 3D geological modeling results based on deep drilling core data reveal that the Sanshandao gold orefield, which was previously considered to consist of several independent deposits, is a supergiant deposit with gold resources of more than 1200 t (including 470 t under the sea area). The length of the major orebody is nearly 8 km, with a greatest depth of 2312 m below sea level and a maximum length of more than 3 km along their dip direction. (2) Thick gold orebodies in the Sanshandao gold deposit mainly occur in the specific sections of the ore-controlling fault where the fault plane changes from steeply to gently inclined, forming a stepped metallogenic model from shallow to deep level. The reason for this strong structural control on mineralization forms is that when ore-forming fluids migrated along faults, the pressure of fluids greatly fluctuated in fault sections where the fault dip angle changed. Since the solubility of gold in the ore-forming fluid is sensitive to fluid pressure, these sections along the fault plane serve as the target areas for deep prospecting. (3) Thermal uplifting-extensional structures provide thermodynamic conditions, migration pathways, and deposition spaces for gold mineralization. Meanwhile, the changes in mantle properties induced the transformation of the geochemical properties of the lower crust and magmatic rocks. This further led to the reactivation of ore-forming elements, which provided rich materials for gold mineralization. (4) It can be concluded from previous research results that the gold mineralization in the Jiaodong gold deposits occurred at about 120 Ma, which was superimposed by nonferrous metals mineralization at 118–111 Ma. The fluids were dominated by primary mantle water or magmatic water. Metamorphic water occurred in the early stage of the gold mineralization, while the fluid composition was dominated by meteoric water in the late stage. The S, Pb, and Sr isotopic compositions of the ores are similar to those of ore-hosting rocks, indicating that the ore-forming materials mainly derive from crustal materials, with the minor addition of mantle-derived materials. The gold deposits in the Jiaodong Peninsula were formed in an extensional tectonic environment during the transformation of the physical and chemical properties of the lithospheric mantle, which is different from typical orogenic gold deposits. Thus, it is proposed that they are named “Jiaodong-type” gold deposits.©2021 China Geology Editorial Office.  相似文献   

Geometry and kinematics of brittle deformation in the Central Cameroon Shear Zone (Kékem area): Implication for gold exploration within the Central Africa Fold Belt in Cameroon     

《China Geology》2021,4(2):245-255

The Central Africa Fold Belt (CAFB) is a collision belt endowed with gold deposits in Eastern Cameroon area mined for about 50 years. However, favorable areas for gold exploration are poorly known. This paper presents (1) the kinematics of the brittle deformation in the Kékem area in the SW portion of the Central Cameroon Shear Zone and (2) constraints gold mineralization events with respect to the collisional evolution of the CAFB. The authors interpret that the conjugate ENE to E and NNW to NW trending lineament corresponds to the synthetic (R) and the antithetic (R’) shears, which accompanied the dextral slip along the NE to ENE striking shear. The latter coincides with the last 570–552 Ma D₃ dextral simple shear-dominated transpression, which is parallel to the Bétaré Oya shear zone hosting gold deposits. Gold mineralizations, which mainly occurred during the last dextral shearing, are disseminated within quartz veins associated to Riedel’s previous structures reactivated due to late collisional activities of the CAFB as brittle deformation. Gold mineralizations occurred mainly during the 570–552 Ma D₃ event. The reactivation, which might be due to dextral simple shear during mylonitzation, plausibly remobilized the early gold deposits hosted in syn-compressional rocks and/or possibly focused deep-sourced fluid mixed with those released by dehydration. Therefore, the Central Cameroon Shear Zone where Kékem is located, and which shows similar petrographical and structural features to those controling Batouri gold district, is a target area for gold exploration in Cameroon.  相似文献   

我国华南江南春季雷暴气候特征分析          下载免费PDF全文

杨波  王园香  蔡雪薇 《热带气象学报》2019,35(4):470-479

基于我国华南江南地区274个基本地面气象观测站数据、全国闪电定位数据以及欧洲中心的全球大气再分析数据(ERA-Interim),对1981—2017年华南江南地区的春季雷暴日采用经验正交函数分解方法(EOF),并与气象要素场做回归分析。得出以下主要结论:(1)我国华南江南地区春季雷暴活动高发区主要在广西东部至广东西部;其高峰期在下午18:00和凌晨4:00左右,且大多数雷暴活动持续时间不超过3 h;山区雷暴活动主要在傍晚至夜间;平原雷暴活动主要在白天,高峰在17:00及06:00前后;(2)华南江南地区的雷暴活动存在着3~5年的短周期和16年左右的长周期变化;(3)雷暴日距平EOF分析的前3个主成分累计方差贡献达到72.3%。按其向量场的方差贡献分型,Ⅰ型表现为华南江南雷暴活跃特征呈现较统一的变化规律。深厚西南低涡槽前、上干下湿的水汽层结、上冷下暖的温度层结为华南江南地区发生大范围雷暴天气提供良好的动力、水汽和位势不稳定条件,是华南江南雷暴活跃异常的主要模态;Ⅱ型表现为从华南南部到江西与浙江南部有一条西南-东北向、下宽上窄的雷暴活跃正距平异常区,而两侧为负距平异常区。其环流特征表现为温度整层偏冷,水汽整层偏湿,而西南槽前动力抬升有利于水汽抬升凝结触发对流形成雷暴;Ⅲ型表现为华南和江南地区雷暴活跃特征呈南北反位相异常,其分界线在26 °N附近。其环流特征表现为较强的干冷空气南下与南方暖湿空气在南岭山区对峙形成异常的垂直环流圈。在其上升支,低层干冷空气被卷入中高层使得中高层暖湿空气凝结释放潜热形成对流,造成华南地区多雷暴发生,而江南地区处于垂直环流的下沉支,整层湿度偏干,造成江南地区雷暴相对偏少。   相似文献   

“三江”北段沱沱河地区的成矿规律与找矿方向   总被引：1，自引：0，他引：1  

宋玉财  侯增谦  王贵仁  李连松  杨天南  张洪瑞  刘燕学  杨竹森  田世洪  刘英超  贾宗涌  汪元奎  刘群  闫明  何利 《矿床地质》2015,34(1):1-20

"三江"成矿带的北段沱沱河地区是中国首批整装勘查区之一,区域成矿规律和找矿方向亟待了解。研究表明,区内主要发育3期成矿事件,形成5种主要矿床类型。早期成矿发生在晚二叠世至早三叠世,为龙木错-双湖洋向北俯冲下的弧间或弧后盆地环境,形成开心岭火山岩容矿块状Fe(-Cu-Zn)矿床(VMS型);第二期成矿作用发生于新生代40~25 Ma期间,对应印-亚大陆晚碰撞环境,形成那日尼亚与钾质火山岩岩浆活动有关的脉状PbZn矿床、扎日根玢岩型铁矿床及扎拉夏格涌与碱性斑岩有关的热液脉状Pb-Zn矿床;第三期矿化出现在新生代23Ma以来,对应印-亚大陆后碰撞环境,形成以茶曲帕查为代表的密西西比河谷型(MVT)Pb-Zn矿床。综合分析表明,区内应优先寻找MVT型矿床,在区域逆冲带的前锋带中,老于新生代的碳酸盐岩内、碳酸盐岩与碎屑岩地层界面附近是找矿的主要方向;晚二叠世至早三叠世及晚三叠世地层中双峰式火山岩建造是寻找VMS矿床的有利部位;新生代闪长玢岩分布区的正磁异常、Cu化探异常、发育绿帘石和绿泥石化的地区有利于寻找玢岩型铁矿床;而热液脉状Pb-Zn矿床的成矿潜力有限。  相似文献   

塔里木盆地塔中—巴楚地区奥陶系内幕不整合     

邓胜徽  杜品德  卢远征  黄智斌  景秀春  张师本  樊茹  杨芝林  李鑫 《地质论评》2015,61(2):324-332

塔里木盆地塔中-巴楚地区奥陶系内部存在一期重要的不整合。通过对数十口钻井的地层、古生物研究及与露头剖面的对比,发现该不整合的顶、底层位变化较大,地层缺失量在不同地区有所差异,可大致分为两种情况:其一是塔中地区,上奥陶统良里塔格组覆于鹰山组第三段(下奥陶统上部)之上,且有部分钻井良里塔格组下部也发育不全,缺失了至少11个牙形石带,相当于有17~20Ma的地层缺失;其二是巴楚地区,良里塔格组覆于鹰山组第二段或鹰山组第一段(中奥陶统下部)之上,缺失了至少8个牙形石带,相当于有约14Ma的地层缺失。上述地层缺失主要是由于中奥陶世以后塔里-巴楚地区出水成陆,碳酸盐岩地层受大气淡水溶蚀的结果。在不整合之下碳酸盐岩地层中形成的岩溶是十分重要的油气储层。因此,对该不整合的研究对于塔中、巴楚地区奥陶系,特别是鹰山组的油气勘探具有重要的意义。  相似文献   

基于模糊评判的数控机床零部件制造工艺FMECA研究     

谭壮  李国发  许彬彬  王松  朱光 《南京气象学院学报》2015,7(2):142-148

以数控机床零部件的制造工艺为研究对象,对其实施改进的制造工艺FMECA,通过梯形模糊数评判的方法确定出工艺FMECA中风险优先数的排序,利用模糊综合评判方法确定出工艺系统的风险等级,有效地找出薄弱工艺环节并采取改进措施,从而提高数控机床零部件制造工艺可靠性.  相似文献   

一种电费管理系统的设计与实现     

贾红云  陈天元 《南京气象学院学报》2015,7(3):227-233

针对供电部门所辖范围内的用户,开发出一种能完成电费管理、信息管理等功能的综合管理系统.该电费管理系统采用B/S模式(浏览器/服务器模式),面向对象语言Java作为编程开发语言,动态网页采用JSP技术来制作,网络数据库则使用MySQL,同时采用JDBC接口连接MySQL数据库,Tomcat作为Web服务器,集成开发环境选择MyEclipse6.6.该系统可以较大地降低电力部门的管理成本,减轻供电系统日常管理的压力.  相似文献   

IMPACT OF TROPICAL INTRASEASONAL OSCILLATIONS ON THE PRECIPITATION OF GUANGDONG IN JUNES     

林爱兰  李春晖  谷德军  郑彬 《热带气象学报(英文版)》2015,21(4):326-336

The impact of tropical intraseasonal oscillations on the precipitation of Guangdong in Junes and its physical mechanism are analyzed using 30-yr (1979 to 2008), 86-station observational daily precipitation of Guangdong and daily atmospheric data from NCEP-DOE Reanalysis. It is found that during the annually first rainy season (April to June), the modulating effect of the activity of intraseasonal oscillations propagating eastward along the equator (MJO) on the June precipitation in Guangdong is different from that in other months. The most indicative effect of MJO on positive (negative) anomalous precipitation over the whole or most of the province is phase 3 (phase 6) of strong MJO events in Junes. A Northwest Pacific subtropical high intensifies and extends westward during phase 3. Water vapor transporting along the edge of the subtropical high from Western Pacific enhances significantly the water vapor flux over Guangdong, resulting in the enhancement of the precipitation. The condition is reverse during phase 6. The mechanism for which the subtropical high intensifies and extends westward during phase 3 is related to the atmospheric response to the asymmetric heating over the eastern Indian Ocean. Analyses of two cases of sustained strong rainfall of Guangdong in June 2010 showed that both of them are closely linked with a MJO state which is both strong and in phase 3, besides the effect from a westerly trough. It is argued further that the MJO activity is indicative of strong rainfall of Guangdong in June. The results in the present work are helpful in developing strategies for forecasting severe rainfall in Guangdong and extending, combined with the outputs of dynamic forecast models, the period of forecasting validity.  相似文献   

中高纬度大气低频模态研究进展   总被引：1，自引：0，他引：1  

张曼  许小峰  闵锦忠  高庆九 《气象科学》2015,35(6):799-806

大气低频模态是导致中高纬地区季节及气候变化的主要因素,加强低频模态动力机制的认识对于提高短期气候预测水平具有十分重要的科研意义和应用价值。由于中高纬大气低频环流本身的复杂性,关于其动力机制的研究仍然是大气动力学中重点难点问题。本文简单回顾了激发维持低频模态的前两种机制,即:外源强迫、气流的纬向非均匀性对大气低频模态的影响。从观测事实和模式结果出发,着重介绍了瞬变波与基本气流相互作用激发维持低频模态的第三种机制,且详细阐述了线性假设条件下,瞬变波与基本气流相互作用的动力机制。本文最后针对瞬变波与基本气流相互作用研究中一些尚未解决的问题进行了讨论。  相似文献   

Simulation of the equatorially asymmetric mode of the Hadley circulation in CMIP5 models     

Juan Feng  Jianping Li  Jianlei Zhu  Fei Li  Cheng Sun 《大气科学进展》2015,32(8):1129-1142

The tropical Hadley circulation (HC) plays an important role in influencing the climate in the tropics and extra-tropics. The realism of the climatological characteristics, spatial structure, and temporal evolution of the long-term variation of the principal mode of the annual mean HC (i.e., the equatorially asymmetric mode, EAM) was examined in model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The results showed that all the models are moderately successful in capturing the HC's climatological features, including the spatial pattern, meridional extent, and intensity, but not the spatial or temporal variation of the EAM. The possible reasons for the poor simulation of the long-term variability of the EAM were explored. None of the models can successfully capture the differences in the warming rate between the tropical Southern Hemisphere (SH) and Northern Hemisphere (NH), which is considered to be an important driver for the variation of the AM. Most of the models produce a faster warming in the NH than in the SH, which is the reverse of the observed trend. This leads to a reversed trend in the meridional gradient between the SH and NH, and contributes to the poor simulation of EAM variability. Thus, this aspect of the models should be improved to provide better simulations of the variability of the HC. This study suggests a possible reason for the poor simulation of the HC, which may be helpful for improving the skill of the CMIP5 models in the future.  相似文献