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首页> 外文学位 >Mineralogy, paragenetic sequence, geochemistry and genesis of the gold and silver bearing Upper Cretaceous mineral deposits, northeastern Turkey.
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Mineralogy, paragenetic sequence, geochemistry and genesis of the gold and silver bearing Upper Cretaceous mineral deposits, northeastern Turkey.

机译：土耳其东北部含白垩纪上层金和银的金，银的矿物学，共生序列，地球化学和成因。

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摘要

The Upper Cretaceous mineralizations, located in northeastern Turkey, are the largest sources of base metals in the country. Vein-type and the volcanogenic massive sulfide-type deposits (VMS) are present and both are closely associated with felsic volcanism of Upper Cretaceous age.; The formation of the volcanogenic massive sulfide deposits is strictly associated with the evolution of a very complex volcanic arc structure formed during Kimmeridgian-Alpine epoch, called “the Eastern Pontid tectonic belt”. The VMS deposits of the region present a specific genetic type, and it is highly similar with well-known Kuroko-type mineralizations of Japan. This volcanic arc contains about 62 massive sulfide deposits along its axial zone.; The volcanogenic massive sulfide mineralizations can be subdivided into three types: black-ore dominated deposits, yellow-ore dominated deposits, and deposits containing black (or semi-black) and yellow ore. The deposits are relatively small in reserves compared to the larger porphyry-type Cu-Mo deposits, but they have much higher base metal contents. The orebodies are mostly lens-shaped and flat lying or slightly tilted. Replacement textures dominate in all of the deposits investigated. Almost all the major occurrences are hosted by felsic rocks. In most of the occurrences, the mineralized hanging wall rocks are overlain by either barren volcanic rocks or by volcano-sedimentary sequence.; Sulfur isotope data from the sulfide minerals revealed a very narrow distribution implying a homogeneous source and formation temperature, possibly from the underlying volcanic rocks. Oxygen isotope data showed that the ore-forming fluids could be seawater or mixed with magmatic waters in origin. Lead isotope data also indicated a homogeneous metal lead source for the VMS deposits and showed a less radiogenic character. Lead isotopes also indicated that the VMS deposits were of 89 my in age.; The VMS deposits contain submicroscopic gold in the form of electrum and petzite. Gold occurrences were found to be restricted to the yellow ore, and gold grains occur mainly within chalcopyrite. Silver occurs in solid solution, especially in tedrahedrite-tennantite and bornite.; The vein-type mineralizations are relatively small in size, but they are rich in base metal contents and they also contain gold and silver. They are structurally controlled and mesothermal in character. Types of mineralizations include open space, replacement, vug-filling, and veins. According to the proposed generalized paragenetic sequence, pyrite and sphalerite with barite and quartz are present in most of the mineralizations. The vein-type deposits of the region contain gold in the form mainly of native gold and electrum. Silver occurs as freibergite and in solid solution in tetrahedrite, pyrite, galena, and zinkenite.; Sulfur isotope compositions for the vein-type deposits also have shown a narrow distribution that can be attributed to a homogeneous source and a narrow range of formation temperatures. The vein-type deposits have more radiogenic lead that may indicate an older or sedimentary source for the metal lead. The geological setting suggests that the Eocene magmatism in the surrounding vicinity could have been a source for the ore-forming fluids and for the extensive faulting. (Abstract shortened by UMI.)
机译：位于土耳其东北部的上白垩统矿床是该国最大的贱金属来源。存在静脉型和火山成因的块状硫化物型沉积物（VMS），两者均与上白垩纪的长石质火山活动密切相关。火山成因的大块硫化物矿床的形成与在基米第纪-高山时期形成的非常复杂的火山弧结构的演化密切相关，被称为“东部庞蒂构造带”。该地区的VMS矿床具有特定的成因类型，与日本著名的黑子型矿床高度相似。该火山弧沿其轴向带含有约62个块状硫化物矿床。火山成因的大块硫化物矿化可分为三种类型：黑矿为主的矿床，黄矿为主的矿床以及含有黑色（或半黑色）和黄色矿石的矿床。与较大的斑岩型Cu-Mo矿床相比，该矿床的储量相对较小，但它们的贱金属含量高得多。矿体大多为透镜状，平躺或略微倾斜。置换质地在所有调查的沉积物中均占主导地位。几乎所有的主要事件都由长英质岩石所包围。在大多数情况下，矿化的悬壁岩石被贫瘠的火山岩或火山沉积序列所覆盖。来自硫化物矿物的硫同位素数据表明分布很窄，暗示着来源和地层温度均匀，可能来自下面的火山岩。氧同位素数据表明，成矿流体可能是海水，也可能是与岩浆水混合的。铅同位素数据还表明，VMS沉积物具有均一的金属铅源，并且放射源性较低。铅同位素还表明，VMS矿床的年龄为89 my。 VMS沉积物中包含以电子和铅锌矿形式存在的亚显微金。发现金矿仅限于黄色矿石，金颗粒主要在黄铜矿中。银以固溶体形式存在，特别是在菱铁矿-钙钛矿和褐铁矿中。脉状矿化的规模相对较小，但它们富含贱金属，并且还含有金和银。它们在结构上受控制且具有中等温度。矿化的类型包括开放空间，置换，洞孔充填和矿脉。根据提出的广义共生序列，大多数成矿中都存在黄铁矿和闪锌矿以及重晶石和石英。该地区的矿脉型矿床主要以天然金和电子的形式包含金。银以贝氏体和固溶体的形式存在于四面体，黄铁矿，方铅矿和锌锌矿中。脉状矿床的硫同位素组成也显示出狭窄的分布，这可归因于均相源和狭窄的地层温度范围。脉型沉积物具有更多的放射源铅，这可能表明金属铅的来源较旧或沉积。地质背景表明，附近的始新世岩浆作用可能是成矿流体和广泛断层的来源。 （摘要由UMI缩短。）

著录项

  • 作者

    Ciftci, Emin.;

  • 作者单位

    University of Missouri - Rolla.;

  • 授予单位 University of Missouri - Rolla.;
  • 学科 Geology.; Geochemistry.; Mineralogy.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 251 p.
  • 总页数 251
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;地质学;矿物学;
  • 关键词

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