藏北革吉北部竟柱山组地球化学与碎屑锆石U- Pb年代学特征及构造意义     

李宝龙  范海滨  朱德全  彭勃  郭平  周磊  李宇飞 《地质学报》2020,94(12):3657-3673

沿班公湖- 怒江缝合带近东西向不连续分布的上白垩统竟柱山组（K 2j）,是洋- 陆转换后的陆相沉积。因其东西向空间跨度较大,其准确的形成时限和砂岩源区的构造环境存在争议。本文采集西藏革吉县北部竟柱山组粗砂岩,对其碎屑锆石进行LA- ICP- MS U- Pb测年和主微量元素分析。样品碎屑锆石U- Pb谐和年龄值范围集中于100~130Ma和150~170Ma;在碎屑锆石年龄频谱图上,主要出现111. 7Ma和160. 1Ma两个峰值。最新的碎屑锆石年龄加权平均值为105. 3Ma,表明竟柱山组应在早白垩世末期之后沉积。SiO 2含量为52. 92%~69. 47%,Al 2O 3含量为5. 22%~14. 34%。高场强元素Ta、Nb、Ti亏损,Hf、Th及REE富集;大离子亲石元素Ba亏损,Rb、K富集。主微量元素特征及判别图解表明,研究区竟柱山组砂岩源区构造背景为大陆岛弧环境,物源为中酸性火成岩。  相似文献   

长江中下游成矿带玢岩铁矿研究新进展及对矿床成因的启示     

赵新福  曾丽平  廖旺  李婉婷  胡浩  李建威 《地学前缘》2020,27(2):197-217

长江中下游成矿带的宁芜和庐枞火山岩盆地中发育了大量与早白垩世(约130 Ma)陆相火山-侵入岩有关的玢岩铁矿。这类矿床的特征为具有磁铁矿-磷灰石-阳起石(透辉石)矿物组合,在国际上一般被称为铁氧化物-磷灰石型(Iron Oxide-Apatite, IOA)或基鲁纳型(Kiruna-type)矿床。玢岩铁矿的概念自20世纪70年代提出以来,其成因就一直存在争议,主要有矿浆、岩浆热液及矿浆-热液过渡的观点。近年来的高精度年代学揭示出宁芜和庐枞盆地内玢岩铁矿在约130 Ma集中爆发成矿。矿物学、岩石学及地球化学的综合研究表明成矿物质主要来源于次火山岩体,且成矿早期流体具有高温(550~780 ℃)和超高盐度(可达90% NaCl_eq)的特点。这些特点与成矿岩体及周围火山岩在成矿早阶段发育大规模钠质蚀变相吻合;但同时S-Sr等同位素和流体包裹体成分分析表明在铁成矿过程中还有外来壳源(如膏盐层物质)流体的加入。一些研究工作还表明玢岩铁矿与夕卡岩型铁矿具有相似的热液蚀变演化过程,暗示两者或许存在某些成因联系,很可能是相似流体与不同性质围岩及在不同温度下水岩交代产物。这些新的证据为探讨玢岩铁矿的成矿作用过程和成因机制提供了新的制约,也带来了新问题。本文从成岩成矿年代学、成矿物质来源、成矿早期流体性质、玢岩铁矿与夕卡岩铁矿及其外围新发现的金铜矿化的成因联系等角度,对近年来长江中下游成矿带玢岩铁矿研究的主要新进展进行初步总结。当前IOA型矿床的成因研究成为国际上矿床学研究的一个热点,除了长期争论的矿浆成因和岩浆热液成因,最近提出多个了岩浆-热液复合成矿模型,如岩浆磁铁矿-气泡悬浮模型及富水铁熔体的上升、脱气和侵位成因模型。将IOA型矿床成因争论的焦点逐渐聚焦在岩浆到岩浆后(岩浆热液)阶段,铁质究竟是以含铁岩浆热液、铁矿浆 (Fe-O或P-Ca-Fe-O),还是岩浆磁铁矿微晶或其他未知的形式来富集成矿的,还有待进一步研究,文章对以上的新模型进行简要介绍和评述,并与长江中下游的矿床进行对比。  相似文献   

Fluorite deposits in China: Geological features,metallogenic regularity,and research progress     

《China Geology》2020,3(3):473-489

Fluorite is one of the important mineral raw materials in the industry. In China, it is mainly distributed in the provinces and regions such as Hunan, Zhejiang, Jiangxi, Inner Mongolia, Fujian, and Henan provinces, boasting huge reserves and large numbers of deposits. However, most of the fluorite deposits are on a small or medium scale. The main fluorite deposits in China were studied in this paper. Their geological features and metallogenic regularity were summarized and compared. Meanwhile, based on their main genetic factors including metallogenic fluid sources and main metallogenic geological processes, they were divided into two groups, namely meso-epithermal deposits and magmatic-hydrothermal deposits. Furthermore, based on the prospecting achievements and research progress obtained in fluorite deposits in recent years, prospecting potential predictions were made for the metallogenic prospect areas and major prospecting areas of fluorite in China. This aims to provide a theoretical basis and direction for future fluorite prospecting in China.  相似文献   

Controls of preferential orientation of earthquake- and rainfall-triggered landslides in Taiwan's orogenic mountain belt     

Yi-Chin Chen  Kang-Tsung Chang  Su-Fen Wang  Jr-Chuan Huang  Cheng-Ku Yu  Jien-Yi Tu  Hone-Jay Chu  Cheng-Chien Liu 《地球表面变化过程与地形》2019,44(9):1661-1674

Landsliding usually occurs on specific hillslope aspect, which may reflect the control of specific geo-environmental factors, triggering factors, or their interaction. To explore this notion, this study used island-wide landslide inventories of the Chi-Chi earthquake in 1999 (M_W = 7.6) and Typhoon Morakot in 2009 in Taiwan to investigate the preferential orientation of landslides and the controls of landslide triggers and geological settings. The results showed two patterns. The orientations of earthquake-triggered landslides were toward the aspect facing away from the epicenter in areas with peak ground acceleration (PGA) ≥ 0.6 g and landslide ratio ≥ 1%, suggesting that the orientations were controlled by seismic wave propagation. Rainfall-triggered landslides tended to occur on dip slopes, instead of the windward slopes, suggesting that geological settings were a more effective control of the mass wasting processes on hillslope scale than the rainfall condition. This study highlights the importance of the endogenic processes, namely seismic wave and geological settings, on the predesigned orientation of landslides triggered by either earthquake or rainfall, which can in turn improve our knowledge of landscape evolution and landslide prediction. © 2019 John Wiley & Sons, Ltd.  相似文献   

Optimization of UAVs-SfM data collection in aeolian landform morphodynamics: a case study from the Gonghe Basin,China     

Wanyin Luo  Mei Shao  Xuehua Che  Patrick A. Hesp  Robert G. Bryant  Changzhen Yan  Zanpin Xing 《地球表面变化过程与地形》2020,45(13):3293-3312

UAVs-SfM (unmanned aerial vehicles-structure-from-motion) systems can generate high-resolution three-dimensional (3D) topographic models of aeolian landforms. To explore the optimization of UAVs-SfM for use in aeolian landform morphodynamics, this study tested flight parameters for two contrasting aeolian landform areas (free dune and blowout) to assess the 3D reconstruction accuracy of the UAV survey compared with field point measurements using differential RTK-GPS (real-time kinematic-global positioning system). The results reveal the optimum UAVs-SfM flight set-up at the free-dune site was: flying height = 74 m, camera tilt angle = −90°, photograph overlap ratio = 85%/70% (heading/sideways). The horizontal/vertical location error was around 0.028–0.055 m and 0.053–0.069 m, respectively, and a point cloud density of 463/m³ was found to generate a clear texture using these flying parameters. For the < 20 m deep blowout the optimum set-up with highest accuracy and the lowest cliff texture distortion was: flying height = 74 m combined camera tilt angle = −90° and −60°, photograph overlap ratio = 85%/70% (heading/sideways), and an evenly distributed GCPs (ground control points) density of 42/km² using these flying parameters. When the depth of the blowouts exceeded 40 m, the optimum flight/survey parameters changed slightly to account for more challenging cliff texture generation: flying height = 80 m (with −90° and −60°combined camera tilt angle), GCPs density = 63/km² to generate horizontal and vertical location error of 0.024 m and 0.050 m, respectively, and point cloud density of 2597.11/m³. The main external factors that affect the successful 3D reconstruction of aeolian landforms using UAVs-SfM are the weather conditions, manipulation errors, and instrument system errors. The UAVs-SfM topographic monitoring results demonstrate that UAVs provide a viable and robust means for aeolian landform morphodynamics monitoring. Importantly, the rapid and high precision 3D reconstruction processes were significantly advanced using the optimal flight parameters reported here. © 2020 John Wiley & Sons, Ltd.  相似文献   

论华夏成矿省——贺陈毓川院士九十华诞          下载免费PDF全文

杨明桂  陈祥云  吴俊华  衷存堤  王岩 《地质论评》2024,70(3):823-838

笔者等对《中国矿产地质志·华南洋—滨太平洋构造演化与成矿》一书（2020）厘定的战略矿产资源居于重要地位的华夏成矿省作些简要论述：①该成矿省处于古华南洋成矿域与滨太平洋成矿域强烈复合地带,历经早前寒武世克拉通—华南洋—华南裂谷系—陆表海—大陆的发展演化,又受到多期造山特别是空前强烈的燕山期陆内活化造山,并且是一个世界级钨地球化学块体,构成了优越的成矿基因;②主要成矿特征：包括华南洋及其陆缘弧盆残体成矿,南华间冰期与冰后期大规模沉积成矿,多期大规模S型岩浆以钨为首的有色、铀、贵金属、非金属成矿,I型岩浆以铜为首的铁、有色、贵金属成矿以及钦杭成矿带超大矿床集群与“深地”找矿之眼等;③燕山运动岩浆与成矿“核幔式”时空演化规律以及多体系复合构造格局与陆洋左行扭动与洋壳俯冲为主导并有板内挤压、地壳蠕散相复合的动力学机制。  相似文献   

与侵入岩有关金矿床的研究现状、存在问题及在中国的前景     

胡朋聂凤军  江思宏 《地质论评》2006,52(4):539-549

与侵入岩有关的金矿床是近年来识别出来的一种新的金矿类型。这类金矿床常在远离汇聚板块边缘的克拉通边缘环境中产出,与已知的W／Sn岩浆省叠加。它们具特征性的Au＋Bi＋W＋Te＋Sb＋As等亲石元素金属组合,在时空上和成因上与中等还原的分异Ⅰ型侵入岩密切相关,随就位深度的不同而显示不同的矿化特征。形成于地壳浅部环境（〈5km）中的金矿床常与岩株、岩墙或岩床有关,金矿化大多数以浅成低温脉、网状脉或角砾岩筒产出;形成于地壳深部环境（〉5km）中的金矿床常与深成侵入岩体有关,金矿化以席状脉、云英岩或浸染状块体产出。流体包裹体研究表明成矿流体的类型随着成矿深度的不同而显示有规律的变化,形成于较浅部环境中的金矿床一般包括高温（〉350C）、不混溶的盐水（〉30％NaCleq）和低盐度（〈5％NaCleq）含CO2液相包裹体;而形成于较深部环境中的金矿床含有大量低盐度含CO2液相（〈10％NaCleq）包裹体,有些矿床晚阶段流体含有中高盐度（10％～40％NaCleq）的盐水。含CO2流体无论在挥发份的出溶过程中还是在金属迁移过程中都起了重要的作用。与侵入岩有关的金矿床在中国有广阔的找矿前景,而中国东部金矿省和钨／锡成矿省的叠加部位是寻找该类型矿床的有利地段。  相似文献   

苏北东海水晶矿床的形成机理初探   总被引：2，自引：1，他引：1       下载免费PDF全文

郑大中  郑若锋 《江苏地质》2009,33(3):239-244

通过对硅的迁移形式和条件、苏北东海水晶矿床中石英流体包裹体的化学成分、部分飘动气体自然、晶洞与水晶的密切相关性以及水晶的共生伴生矿物等的研究,提出该矿床的形成机制为：在地球深部高温高压强还原富氢环境下,硅呈气态硅氢络合物活化并纯化、迁移至地壳浅部低温低压氧化环境,硅氢化物较快氧化形成石英脉,并在有利部位形成石英外壳（晶洞壳）,晶洞内的硅氢化物在温和稳定环境中缓慢氧化,并自由结晶分异纯化形成水晶矿床。  相似文献   

中国大陆科学钻探工程主孔榴辉岩原岩研究及其成因指示          下载免费PDF全文

叶景艳  胡建  汤倩 《江苏地质》2013,37(1):1-16

榴辉岩是造山带中最为常见的高级变质岩石,无论是自身还是其原岩均蕴含着丰富的地球动力学信息。以中国大陆科学钻探工程主孔0～2000m范围内揭露的榴辉岩为对象,按其与围岩接触关系,划分为与片麻岩类共生的榴辉岩、与超基性岩毗邻的榴辉岩以及与超基性岩共生的榴辉岩3种类型。据此对比分析了此3类榴辉岩的地球化学组成的差异,提出了这些岩石的原岩可能是由单一岩浆房岩浆经堆晶及分离结晶作用演化而来的基性—超基性杂岩体,物质来源主要为富集地幔物质的部分熔融,其构造环境应位于洋壳对大陆俯冲的消减带,但并非岛弧环境,应是弧后拉张岩浆作用的产物。  相似文献   

甘肃岷县寨上金矿成矿年代及矿床成因探讨SCIEI北大核心CSCD          下载免费PDF全文

王宇昊  杜志伟  焦学尧  马锦龙 《岩石学报》2022,38(4):1237-1252

寨上金矿位于西秦岭大规模卡林-类卡林型金矿床集中地之中,是近二十年来探获的又一超大型金矿。通过对寨上金矿的6件矿石样品中的载金矿物黄铁矿进行Rb、Sr、Re、Os同位素分析,获得Rb-Sr、Re-Os等时线年龄分别为273±10Ma、273Ma±22Ma。该数据大于前人所获的二期成矿阶段年龄,在西秦岭已探明的金矿床中尚无报道,反映了寨上金矿更早一期的成矿年龄为273Ma,这也为该区域寻找金矿床拓宽了时间轴。Sr、Os、S同位素及稀土和微量元素研究表明,寨上金矿成矿物质为深源与壳源物质的混合。二叠纪时位于岷礼前陆盆地的吴家山隆起经历了强烈的隆升延展作用,岩浆热液沿断裂通道上升到有较高Au背景值盆地中的褶皱带,使地层中的Au活化富集,在构造有利部位卸载成矿,形成早期寨上金矿床,后期钨矿化及金矿化叠加在早期金矿床之上。寨上金矿第一期金成矿的年龄在时空上与阿尼玛卿洋盆闭合、共和坳拉谷俯冲碰撞、江里沟及中川喜马拉雅型岩体的侵入时间基本吻合,符合“地壳加厚有利于形成金矿床及喜马拉雅型花岗岩与金矿关系密切”的结论,对在该区域寻找同时代金矿床具有一定的指示意义。  相似文献