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1.
Ronchetti  F.  Deiana  M.  Lugli  S.  Sabattini  M.  Critelli  V.  Aguzzoli  A.  Mussi  M. 《Hydrogeology Journal》2023,31(3):601-619
Hydrogeology Journal - The Poiano karst spring is located in the North Apennines (Italy) and it drains Triassic evaporite rocks with a mean discharge of hundreds of liters/second. Two...  相似文献   

2.
西秦岭地区造山型与卡林型金矿床   总被引:33,自引:0,他引:33  
西秦岭金矿床分为卡林型和造山型两类。卡林型金矿床麇集于南秦岭和松潘—甘孜造山带的东北部。三叠纪和早侏罗世的同构造花岗闪长岩广泛分布于西秦岭中部和南部、松潘—甘孜盆地以及扬子克拉通边缘。造山型脉状金矿床主要分布于西秦岭造山带中的脆韧性剪切带内。大部分粗粒金主要赋存在网格状石英细脉和角砾状围岩中的黄铁矿、磁黄铁矿、毒砂和少量贱金属硫化物中和以分散状分布在蚀变围岩中。同位素资料表明晚三叠世 -中侏罗世与扬子克拉通俯冲有关的作用控制了造山型金矿床的形成。  相似文献   

3.
The Middle-Lower Yangtze (Changjiang) River Valley metallogenic belt is located on the northern margin of the Yangtze Craton of eastern China. Most polymetallic deposits in the Changjiang metallogenic belt are clustered in seven districts where magmatism of Mesozoic age (Yanshanian tectono-thermal event) is particularly extensive. From west to east these districts are: E-dong, Jiu-Rui, Anqing-Guichi, Lu-Zong, Tong-Ling, Ning-Wu and Ning-Zhen. World-class iron ore deposits occur in the Lu-Zong and Ning-Wu ore clusters, which are mainly located in continental fault-bound volcanic-sedimentary basins. One of these deposits is the Longqiao iron deposit, discovered in the northern part of the Lu-Zong Basin in 1985. This deposit consists of a single stratabound and stratiform orebody, hosted in sedimentary carbonate rocks of the Triassic Dongma'anshan Formation. A syenite pluton (Longqiao intrusion) is situated below the deposit. The iron ore is massive and disseminated and the ore minerals are mainly magnetite and minor pyrite. Wall rock alteration mostly consists of skarn minerals, such as diopside, garnet, potassic feldspar, quartz, chlorite, phlogopite and anhydrite. Thin sedimentary siderite beds of Triassic age occur as relict laminated ore at the top and the margin of the magnetite orebody. These sideritic laminae are part of Triassic evaporite-bearing carbonate deposits (Dongma'anshan Formation).Sulfur isotopic compositions show that the sulfur in the deposit was derived from a mixture of magmatic hydrothermal fluids and carbonate–evaporite host rocks. Similarly, the C and O isotopic compositions of limestones from the Dongma'anshan Formation indicate that these rocks interacted with magmatic hydrothermal fluids. The O isotopic compositions of the syenitic rocks and minerals from the deposit show that the hydrothermal magnetite and skarn minerals were formed from magmatic fluids. The Pb isotopic compositions of sulfides are similar to those of the Longqiao syenite. Phlogopite coexisting with magnetite in the magnetite ores yielded a plateau age of 130.5 ± 1.1 Ma (2σ), whereas the LA-ICP MS age of the syenite intrusion is 131.1 ± 1.5 Ma, which is slightly older than the age of phlogopite.The Longqiao syenite intrusion may have crystallized from a parental alkaline magma, generated by partial melting of lithospheric mantle, during extensional tectonics. The ore fluids were probably first derived from magma at depth, later emplaced in the sedimentary rocks of the Dongma'anshan Formation, where it interacted with siderite and evaporite-bearing carbonate strata, resulting in the formation of magnetite and skarn minerals. The Longqiao iron deposit is a skarn-type stratabound and stratiform mineral system, genetically and temporally related to the Longqiao syenite intrusion. The Longqiao syenite is part of the widespread Mesozoic intracontinental magmatism (Yanshanian event) in eastern China, which has been linked to lithospheric delamination and asthenospheric upwelling.  相似文献   

4.
The Qinghai-Tibet Plateau located in the Tethyan tectonic domain is the best developed region of Mesozoic and Cenozoic marine sediments in China. The Qiangtang basin is the biggest and relatively stable area of the plateau. Triassic and Jurassic hydrocarbon source rocks are extensively distributed in the basin. There exist good dolomite and organic reef reservoirs and mudstone and evaporite cap rocks, as well as well-developed structural traps in the basin; in addition destroyed petroleum traps have been discovered. Therefore, the conditions of petroleum geology in the Qiangtang basin are excellent  相似文献   

5.
The lower valley of Changjiang, from Wuhan of the Hubei Province in the west to Zhenjiang of the Jiangsu Province in the east, contains more than 200 polymetallic (Cu–Fe–Au, Mo, Zn, Pb, Ag) deposits and is one of the most important metallogenic belts in China. This metallogenic belt, situated at the northern margin of the Yangzi craton and bordered by the Dabieshan ultrahigh pressure metamorphic belt to the north, consists mainly of Cambrian–Triassic marine clastic sedimentary rocks and carbonate and evaporite rocks, which overlay a Precambrian basement and are intruded by Yanshanian (205 to 64 Ma) granitoid intrusions and subvolcanic complexes. Repeated tectonism from Late Proterozoic to Triassic resulted in extensively developed networks of faults and folds involving the Cambrian–Triassic sedimentary strata and the Precambrian basement. The Yanshanian granitoid intrusions and subvolcanic complexes in the Lower Changjiang metallogenic belt are characterized by whole-rock δ18O of +8‰ to +10‰, initial 87Sr/86Sr of 0.704 to 0.708, and εNdt from −10 to −17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials. Also, the Yanshanian granitoids exhibit eastward younging and increase in alkalinity (i.e., from older calc–alkaline in the west to younger subalkaline–alkaline in the east), which are related to oblique collision between the Yangzi and Sino-Korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes. Most polymetallic deposits in the Lower Changjiang metallogenic belt are clustered in seven districts where the Yanshanian magmatism is particularly extensive: from west to east, Edong, Jiurui, Anqing–Guichi, Luzhong, Tongling, Ningwu and Ningzhen. Mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits: orebodies in Yanshanian granitoid intrusions, skarn orebodies at the contact zones between the Yanshanian intrusions and Late Paleozoic–Early Mesozoic sedimentary rocks, and stratabound massive sulfide orebodies in the Late Paleozoic–Early Mesozoic sedimentary strata. The most important host sedimentary strata are the Middle Carboniferous Huanglong Formation, Lower Permian and Lower–Middle Triassic carbonate and evaporite rocks. The intrusion-hosted and skarn orebodies exhibit well-developed zonation in alteration assemblages, metal contents, and isotopic compositions within individual deposits, and apparently formed from hydrothermal activities related to the Yanshanian magmatism. The stratabound massive sulfide orebodies in the Late Paleozoic–Early Mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano-sedimentary exhalative processes in shallow marine environments. However, extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization. On the basis of geological relationships and isotope geochemical characteristics, we propose a carbonate-hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies. This model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the Yanshanian intrusions with carbonate and evaporite wall rocks. Mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion-hosted orebodies. The stratabound massive sulfide deposits of the Lower Changjiang metallogenic belt share many features with the well-studied, high-temperature, carbonate-hosted replacement deposits of northern Mexico and western United States, particularly with respect to association with small, shallow granitoid complexes, structural and stratigraphic controls on mineralization, alteration assemblages, geometry of orebodies, metal association, metal zonation and isotopic systematics.  相似文献   

6.
经野外调研和室内研究,对老挝华潘省香科菱镁矿的矿区地质、矿体、围岩与夹石、矿石特征和矿床成因取得了一些新的认识。该矿区出露地层为下古生界(Pz1)、中-上石炭统(C2-3)和第四系河流二级阶地沉积(Qpal),主要构造为1条北西向逆断层和4条北东向平移断层。矿体产于逆断层南西侧的强烈构造变形带中,呈脉状产出,厚度为数mm至10余cm,共圈出10个矿体。矿体的围岩与夹石的岩石类型相同,为浅变质陆源碎屑岩,具高硅(w(SiO2)为81.190%)、低镁(w(MgO)为0.781%)、富铁(w(Fe2O3)为11.716%、w(FeO)为1.719%)特征。矿石矿物为菱镁矿,脉石矿物主要为石英、金云母、白云石、绢云母和褐铁矿。香科菱镁矿的形成过程是:在中-晚三叠世的古特提斯洋封闭过程中,镁质从超镁铁岩中析出形成含矿热液,含矿热液迁移与富集后在强烈构造变形带中形成网脉状菱镁矿。香科菱镁矿的成因类型属产于浅变质碎屑岩中之老挝香科式晶质菱镁矿热液型矿床,成矿时代属中-晚三叠世。  相似文献   

7.
闽西南晚三叠世文宾山组碎屑锆石U-Pb年龄及地质意义   总被引:4,自引:0,他引:4  
日益增多的资料表明中国东南沿海并不是后加里东地台,而是由不同地块拼贴而成。闽西南晚三叠世文宾山组具有类磨拉石沉积特征,其盆地沉积物碎屑锆石U-Pb年龄信息,可以为了解盆地源区组成及其变化及区域构造演变过程研究提供约束。闽西南晚三叠世文宾山组碎屑锆石形态学及U-Pb测年分析表明:(1)晚三叠世文宾山组物源复杂,其主要源区是闽西北隆起带;(2)闽西南晚三叠世具有大于2500 Ma的太古宙的源区,华夏古陆可能存在太古宙陆核或东南沿海还存在另一古老基底;(3)980~1190 Ma的碎屑锆石说明晚三叠世闽西南具有G renville期物质来源,它们可能来自另外一个陆块,由于印支期古特提斯洋关闭与华夏地块拼接,并为晚三叠世盆地提供物源;(4)区内印支期岩浆岩带也是晚三叠世沉积的重要物源区。  相似文献   

8.
若尔盖巴西金矿床铜锌矿(Cu2Zn)的发现及其地质意义   总被引:5,自引:1,他引:4  
罗梅  王月文 《矿物学报》1999,19(1):20-22
若尔盖巴西金矿床产于中上三叠统碎屑岩与印支-燕山期闪长岩入体的接触过渡带中,金矿化围冉为交代硅化石英岩,在矿石中发现铜矿矿。该矿物为缺氧、硫并在较高熔融温度的强还原环境中的产物,根据本区含矿岩石中发现火山凝灰质碎屑岩及邻区三叠纪时期存在区域裂陷与岩浆活动的特点,认为巴西金矿的成矿来源与海底火山喷发作用有关。  相似文献   

9.
四川盐源盐矿成盐成钾分析预测   总被引:1,自引:0,他引:1       下载免费PDF全文
李金锁 《地质与勘探》2013,49(4):620-629
四川盐源盆地盐矿成盐于早、中三叠世时期,区域构造复杂,经历多期次的构造变动与演化,在成盐后经历了种种的基底反复变动后形成盐矿底辟构造。以前在该区域做过多方面的研究工作,其中包括三叠纪岩相古地理及生物古地理、三叠系地层、区域古构造演化及水化学分析、物探、钻探等勘探工程。通过这些工作可以证实,盐源盆地在早、中三叠世,经历了蒸发岩盆地的发育阶段。盆地不仅发育有石膏夹层,而且保存有石盐层及含盐卤水层,但有盐无钾。通过对上覆的陆相古近纪和新近纪盆地中出现的三叠系岩盐层和盐丘的研究发现,它们与基底为含盐的海相蒸发岩有一定的内在联系,尽管还不能确定其盐、钾资源前景,但可以确定该区域有成钾盐矿藏的条件和可能,因此,该盆地有可能成为深入研究成盐找钾的重点地区。  相似文献   

10.
玉东-玛东构造带位于塔里木盆地,是在中寒武统膏盐层上滑脱的大规模褶皱冲断带,内部发育多种断层相关褶皱。目前对此构造带的研究,多关注了构造带的局部以及断裂变形。本文根据断层相关褶皱理论,利用地震资料,分析了玉东-玛东构造带内构造样式上的差异性,并通过二维构造正演模拟,建立了典型构造样式的运动学模式。认为研究区内玉东、玛东、塘北3个分区,具有不同的构造样式。玉东地区主要发育和铲式逆断层相关的断弯褶皱,玛东、塘北地区则发育断层突破的滑脱褶皱,突破断层在玛东地区为铲式断裂,而在塘北地区为坪-坡-坪式断裂。根据上奥陶统变形特征及其顶面不整合面之上的地层年代,认为玉东-玛东构造带的变形始于晚奥陶世,主要断裂及其相关褶皱形成于晚奥陶世末期。玉东地区在晚奥陶世早期,形成基底-盖层的低幅褶皱,在晚奥陶世末,形成铲式断裂及断弯褶皱;玛东和塘北地区变形发生在上奥陶统沉积之后,经历了滑脱褶皱和断层突破阶段。通过对比分析认为,断层相关褶皱样式的差异,与膏盐层岩性、厚度,上奥陶统岩性、厚度及构造转换作用有关。本研究有助于完善对塔里木盆地早古生代末期构造变形及演化的认识。  相似文献   

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