The Early Valanginian ammonite, brachiopod and crustacean fauna of the Mecsek Mts. and its relationships with the embryonic shallow water hydrothermal vent at Zeng?várkony (Mecsek Mts., South Hungary)     

László Bujtor 《Cretaceous Research》2011,32(5):565-574

Early Cretaceous development of the Mecsek Mts. (South Hungary) is characterized by continental rifting that produced mixed volcano-sedimentary rocks in the Tihonian/Berriasian and built up a volcanic edifice in the earliest Cretaceous of ankaramite-alkaline basalts. During the Valanginian, marl sedimentation occurred in the basinal part containing rich pelagic fauna dominated by ammonites. Beside phylloceratids, lytoceratids and haploceratids, Kilianella roubaudiana, K. lucensis, Sarasinella eucyrta, Thurmanniceras pertransiens, Th. (Clavithurmannia) foraticostata, Busnardoites campylotoxus, Olcostephanus drumensis, O. densicostatus, and Sabbaiceras stefanescui are indicating the Early and Late Valanginian Thurmanniceras pertransiens, Busnardoites campylotoxus and Saynoceras verrucosum zones. The Early Valanginian is also supported by Calpionellites darderi indicating the calpionellid “E” zone. The marl sequence contains a turbidite bed with rich fauna of shallow marine origin from the volcanic slope of lagoonal, reef, and tidal environs, however it contains metasomatized limestone olistoliths of different origin. Source of these olistoliths is the near iron-ore deposit, which is considered an embryonic shallow water hydrothermal vent. It includes a remarkable fauna of rich crustacean coprolite ichnospecies of Favreina dispentochetarius, F. hexaochetarius, F. octoochetarius, Palaxius decaochetarius, P. tetraochetarius, P. triochetarius. In the neighbourhood of the embryonic vent, a remarkable megafauna occurs, which is an almost monospecific brachiopod fauna dominated by Lacunosella hoheneggeri. Other brachiopods as Nucleata veronica, Moutonithyris moutoniana, Karadagithyris sp., and Zittelina pinguicula also occur as stray individuals. Together with benthic megafauna, nektonic elements as Nautiloidea gen. et sp. ind, phylloceratid- and lytoceratid ammonites and echinoid spines of Balanocidaris rysacantha occur.  相似文献   

Pyrite–anhydrite–magnetite–pyroxene-type deposits and coexisting hydrothermal fluids in Mesozoic volcanic basins, Yangtze River Valley, China     

Ronghua Zhang  Xuetong Zhang  Shumin Hu 《Ore Geology Reviews》2011,43(1):315-332

Anhydrite–pyrite–magnetite–pyroxene–type deposits occur in the Mesozoic volcanic areas of the Middle–Lower Yangtze Valley in China. These deposits are hosted in alkaline basaltic rocks, and are generally accompanied by melanocratic and leucocratic alteration zones, both of which are characterized by a distinct vertical zonation pattern. Investigation of these zones indicates that the chemical compositions of solid solutions and polymorphs of various minerals vary spatially in the alteration profile, upwards from the lowest level, and outwards from the center.Here we report a case study on the Luohe deposit. In the melanocratic-alteration zone, the composition of magnetite (including trace elements Ti, V, Mg, Mn), pyroxene (Mg, Fe²⁺, Fe³⁺, Al₂O₃), plagioclase (An_xAb_{1 − x}), pyrite (Co, Ni) and apatite (F, CeO₂ + Y₂O₃ + La₂O₃) changes with depth. The isotherms of hydrothermal fluids determined from fluid inclusion data, including homogenization temperature and salinity, also vary with depth.Activity diagrams were constructed from mineral and isotherm analysis to estimate the chemical constraints on the alteration-mineral assemblages and the coexisting hydrothermal solutions for the Na₂O–K₂O–CaO–MgO–FeO–Fe₂O₃–A1₂O₃–SiO₂–H₂SO₄–H₂S–HCI–H₂O system at 350 to 600 °C and 500 bars (50 MPa), assuming that the major alteration mineral assemblages along the profile reflect the nature of the coexisting hydrothermal solutions. The activity diagrams adopted the major minerals as buffers to fix the activities of the aqueous species in the system, simulating the physicochemical conditions of the magnetite–anhydrite–pyroxene equilibrium and of solid solutions of diopside–hedenbergite, grossular–andradite and anorthite–albite found in the profile.This study provides an approach to modeling the chemical constraints of coexisting fluids in ore-alteration zones based on field observations.  相似文献   

云南景谷岔河铜矿控矿因素     

孙福伟  付义琴 《云南地质》2011,30(3):312-315

芒亨河断裂的次级断裂是主要控矿构造,含矿围岩为上三叠统小定西组(T3xd)富钠质安山岩、玄武岩。受构造、层位、碎屑粒度的制约。  相似文献   

云南沧源羊缅金矿成因     

高李阳  王爱萍 《云南地质》2011,30(3):273-274

羊缅金矿位于昌宁-孟连有色金属贵金属成矿带,金矿受压扭性断裂控制,分布于变余辉长辉绿岩中,典型的低温热液蚀变型金矿床。  相似文献   

南太平洋东部劳盆地扩张中心表层沉积物中甘油二烷基甘油四醚脂类化合物的组成特征及生物地球化学意义          下载免费PDF全文

陈固魁  胡建芳  杨群慧  彭平安 《海洋与湖沼》2011,42(3):343-350

通过对南太平洋劳盆地东部扩张中（ELSC）表层沉积物样品中甘油二烷基甘油四醚脂类化合物（GDGTs）的分析结果表明,所有样品均检测出类异戊二烯GDGTs和支链GDGTs。其中,类异戊二烯GDGTs占总GDGTs的58．1％-93．4％,泉古菌醇（crenarchaeol）、GDGTⅠ和GDGTⅤ为其主要组分,说明古菌对...  相似文献   

Chemical fluid transport (CFT): A window into Earth and its development     

Werner Schrön 《Chemie der Erde / Geochemistry》2013

Gas phase transport according to chemical fluid transport (CFT) in Earth's crust as well as in the solar nebula is characterized by very high transport efficiency. Systematic investigations of mobilization, transport and deposition of gaseous MeX (Me = metal, X = F or Cl) compounds by solid gas equilibrium reactions are suitable to explain numerous extensive accumulations of minerals and ores. More than 40 of the considered chemical elements form volatile MeX compounds. Some elements tend to form MeF compounds, whereas others are more likely to form MeCl compounds. Silicon reacts with HF to form SiF₄ and replaces other elements to form MeF compounds at low temperature ranges. Accumulations caused by SiF₄ transport explain the formation of numerous quartz varieties and silicate minerals in Earth's crust. Iron most likely reacts with HCl to form FeCl₂ as well as FeCl₃ and explain the formation of iron or iron compounds. Thermodynamically directed transport from cool to hot areas in connection with cyclic processes increases the transport efficiency of MeX-species. Such species are SiF₄, Al₂F₆, POF₃, Cu₃Cl₃, SnCl₄, BF₃, GeF₄, GeCl₄, Ga₂Cl₆, ZrF₄, NbF₅ and TiF₄. The transport gases SiF₄ and POF₃ often react with environmental compounds forming pneumatolytic and metasomatical mineral accumulations. CFT is the “motor” of pneumatolytic and metasomatical processes.  相似文献   

The origin of the Maozu carbonate-hosted Pb–Zn deposit,southwest China: Constrained by C–O–S–Pb isotopic compositions and Sm–Nd isotopic age     

《Journal of Asian Earth Sciences》2013

The Maozu Pb–Zn deposit, located on the western margin of the Yangtze Block, southwest China, is a typical carbonate-hosted deposit in the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province with Pb + Zn reserves of about 2.0 million tonnes grading 4.15 wt.% Pb and 7.25 wt.% Zn. Its ore bodies are hosted in Sinian (635–541 Ma) Dengying Formation dolostone and show stratiform, vein and irregular textures. Ores are composed of sphalerite, galena, pyrite, calcite, dolomite, quartz and fluorite with massive, banded, disseminated and veined structures. The C–O–Sm–Nd isotopic compositions of hydrothermal calcites and S–Pb isotopic compositions of sulfides were analyzed to constrain the origin of the Maozu deposit. δ¹³C_PDB and δ¹⁸O_SMOW values of hydrothermal calcites range from −3.7‰ to −2.0‰ and +13.8‰ to +17.5‰, respectively, and plot near the marine carbonate rocks field in a plot of δ¹³C_PDB vs. δ¹⁸O_SMOW, with a negative correlation. It suggests that CO₂ in the hydrothermal fluids was mainly originated from marine carbonate rocks, with limited influence from sedimentary organic matter. δ³⁴S_CDT values of sulfides range from +9.9‰ to +19.2‰, similar to that of Cambrian to Triassic seawater sulfate (+15‰ to +35‰) and evaporate (+15‰ to +30‰) in the Cambrian to Triassic sedimentary strata. It suggests that reduced sulfur was derived from evaporate in sedimentary strata by thermo chemical sulfate reduction. Sulfides have low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.129–18.375, ²⁰⁷Pb/²⁰⁴Pb = 15.640–15.686 and ²⁰⁸Pb/²⁰⁴Pb = 38.220–38.577) that plot in the field between upper crust and the orogenic belt evolution curve in the plot of ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb, and similar to that of age corrected Proterozoic basement rocks (Dongchuan and Kunyang Groups). This indicates that ore-forming metals were mainly derived from basement rocks. Hydrothermal calcite yields a Sm–Nd isotopic age of 196 ± 13 Ma, possibly reflecting the timing of Pb–Zn mineralization in the SYG province, younger than the Permian Emeishan mantle plume (∼260 Ma). All data combined suggests that hydrothermal fluids circulated through basement rocks where they picked up metals and migrated to surface, mixed with reduced sulfur-bearing fluids and precipitated metals. Ore genesis of the Maozu deposit is different from known magmatic–hydrothermal, Sedimentary Exhalative or Mississippi Valley-types, which maybe represent a unique ore deposit type, named as the SYG-type.  相似文献   

云南维西娃渣铁铅锌多金属矿床     

黄跃  王炳华  罗光明  胡清华 《云南地质》2013,(4):429-432,442

矿床属与中三叠统中酸性火山岩有关的喷流型（或火山沉积改造型）铁铅锌多金属矿,并受地层构造双重控制.  相似文献   

云南兰坪罗善铅锌矿控矿因素及成因     

徐兴业  黄发梅  张桂银  苏泰民  黄联飞 《云南地质》2013,(4):421-423,416

铅锌矿赋存于上三叠统三合洞组下段（T3s1）灰岩容矿岩层中及近南北向、北北东向、北西向断裂破碎带内,少数赋存在近东西向节理裂隙中,成因具多成矿阶段、多成矿物质来源特征,层位＋构造控制的中低温热液型铅锌多金属矿床.  相似文献   

内蒙古科右前旗保隆南沟-老敖沟银铅锌矿成矿地质特征及找矿前景     

伍光锋 《化工矿产地质》2013,(1):21-26

通过对内蒙古保龙南沟-老敖沟银铅锌矿成矿地质特征的分析研究,认为该区矿体严格受构造蚀变带控制,属于典型的热液型银铅锌矿床,且矿区深部及周边地区尚有较大的找矿远景。  相似文献