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Gold Rush as it Happens in Minas Gerais, Brazil: Geological Reconnaissance and Origin of Gold Nuggets 巴西米纳斯吉拉斯州的淘金热:地质勘察和金块的起源
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s1075701524600087
Alexandre Raphael Cabral, José Maria Leal, Rogerio Kwitko-Ribeiro

Abstract

Gold nuggets, loose in talus material, triggered an ongoing gold rush in the southern Serra do Espinhaço, Minas Gerais, Brazil. The talus material has abundant fragments of vein quartz in a clay-rich matrix, resting on metagreywacke of the Neoproterozoic Macaúbas Group. Quartz lodes, which truncate the metamorphic foliation of the bedrock metagreywacke, are the source of the gold nuggets, which formed after the main tectonic and metamorphic overprint of the Ediacaran–Cambrian Brasiliano orogeny. The gold nuggets are hypogene in origin, but they have a minor component of supergene gold, which occurs as dendrites of bud-like gold particles, mostly <1 µm across. Amongst the latter, apically branched hyphae of essentially pure gold are noteworthy and suggest pseudomorphism after fungi.

摘要巴西米纳斯吉拉斯州南部塞拉杜埃斯平哈索(Serra do Espinhaço)的金块散落在距骨材料中,引发了持续不断的淘金热。距石材料中有大量的脉石英碎片,基质富含粘土,位于新新生代马考巴斯组的岩屑岩上。在埃迪卡拉纪-寒武纪巴西里亚诺造山运动的主要构造和变质叠压作用之后形成的石英矿脉截断了基岩玄武岩砾岩的变质褶皱,是金块的来源。金块的来源是次生金,但其中有少量超生金,以芽状金粒的树枝状出现,直径大多为 1 微米。在后者中,值得注意的是顶端分枝的基本上是纯金的菌丝,这表明它们是仿真真菌的假形态。
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引用次数: 0
Genetic Classification of Bauxites of Futa Jallon-Mandingo Province (West Africa) by Textural and Structural Features 根据纹理和结构特征对富塔贾隆-曼丁戈省(西非)的铝土矿进行遗传分类
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s107570152470020x
D. A. Vnuchkov, N. M. Boeva, M. A. Makarova, E. S. Shipilova, V. I. Mamedov, N. S. Bortnikov

Abstract

In the process of the formation of classical lateritic bauxites in the Futa Jallon-Mandingo province, due to a complex of two- to three-stage genesis, lithological and genetic types of bauxites were formed that differed in external characteristics, color, texture, and structure. The proposed genetic typification of bauxite based on textural and structural features of the rocks in fact is the basis for the geological and industrial classification of deposits of the region. Studying the textural and structural features of bauxites is the only way through which one can get an idea of the conditions of their formation. It is in the textures and structures of ores their genetic history is imprinted. The analysis shows that the deposits, within which deposits of sedimentary-lateritic and chemically transformed bauxites predominate, are distinguished not only by greater thicknesses of ore bodies and a significantly higher content of total alumina in the ores, but also by increased contents of monohydrate forms. This also determines various economic indicators of the operation and technology of metallurgical processing of bauxite.

摘要 在富塔贾隆-曼丁戈省古典红土铝土矿的形成过程中,由于两到三个阶段的复杂成因,形成了在外部特征、颜色、质地和结构上各不相同的铝土矿岩性和遗传类型。根据岩石的纹理和结构特征提出的铝土矿遗传类型实际上是该地区矿床地质和工业分类的基础。研究铝土矿的纹理和结构特征是了解其形成条件的唯一途径。矿石的纹理和结构是其遗传历史的印记。分析表明,以沉积-红土沉积和化学转化铝土矿为主的矿床,不仅矿体厚度大,矿石中总氧化铝含量高,而且一水合物含量也高。这也决定了铝土矿冶金加工操作和技术的各种经济指标。
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引用次数: 0
Chemical Mapping of Trace Elements in Pyrite Provides Insight into Mineralizing Processes: the Example of the Neoarchean Cu–Au Porphyry System of the Chibougamau Area, Canada 黄铁矿中微量元素的化学成分图揭示成矿过程:以加拿大 Chibougamau 地区的新元古代铜金矿斑岩系统为例
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s1075701524600051
Lucie Mathieu, Dany Savard, Andrey Kulynych-Rinta

Abstract

Archean porphyry-style mineralization is one of the sources of Au and Cu in greenstone belts. Archean porphyries have been modified by regional deformation and late fluid circulation, and questions remain on the timing of Au mineralization. Indeed, Au may have been introduced at the magmatic-hydrothermal (porphyry) stage, or by a post-magmatic hydrothermal fluid (overprinting orogenic gold system), or a combination of these two processes. Using the Cu–Au Corner Bay deposit as a case study and high-quality chemical mapping performed using laser ablation coupled to a time-of-flight mass spectrometer (LA-FF-ICP-ToF-MS), this study demonstrates that pyrite chemistry has the potential to reconstitute the metallogenic model for Archean porphyry systems. The Corner Bay deposit is associated with the ~2718–2715 Ma Chibougamau pluton, located in the northeastern corner of the gold-endowed Abitibi greenstone belt. Pyrite chemistry points to the following succession of events at Corner Bay: (1) an early porphyry stage that produced pyrite-mineralized quartz-anhydrite veins associated to chloritization and sericitization; (2) followed by a porphyry stage that includes brecciation in response to fluid overpressure and deposition of Cu-Au mineralization by magmatic-hydrothermal fluids with a multi-metal signature (Cu, Ag, Bi, Te, etc.); and (3) a post-porphyry deformation event(s) that induced parallel fracturing and minor carbonatization. This study proposes that, at Corner Bay, Au was introduced during the porphyry-stage of mineralization and was neither remobilized, nor further introduced, during the ~2700 Ma regional deformation stage that is coeval with most orogenic gold-style of mineralization in the southern part of the Abitibi greenstone belt.

摘要 阿歇安斑岩型矿化是绿岩带金和铜的来源之一。由于区域变形和晚期流体循环对阿尔奇岩斑岩进行了改造,金矿化的时间仍然存在疑问。事实上,金可能是在岩浆-热液(斑岩)阶段引入的,也可能是由岩浆后热液流体(叠加造山金系统)引入的,或者是这两个过程的结合。本研究以角湾铜金矿床为案例,利用激光烧蚀耦合飞行时间质谱仪(LA-FF-ICP-ToF-MS)绘制了高质量的化学图谱,证明黄铁矿化学有可能重建阿歇安斑岩系统的成矿模式。Corner Bay矿床与约2718-2715Ma的Chibougamau岩体有关,该岩体位于蕴藏金矿的阿比提比绿岩带的东北角。黄铁矿化学成分表明 Corner Bay 发生了以下事件:(1) 早期斑岩阶段产生了黄铁矿化的石英-软玉矿脉,并伴有绿泥石化和绢云母化;(2) 随后是斑岩阶段,包括流体超压引起的角砾岩化,以及岩浆-热液造成的铜-金矿化沉积,具有多金属特征(铜、银、铋、碲等);(3) 后斑岩阶段,包括流体超压引起的角砾岩化,以及岩浆-热液造成的铜-金矿化沉积,具有多金属特征(铜、银、铋、碲等)。3)斑岩后变形事件,诱发平行断裂和轻微碳酸盐化。本研究认为,在 Corner Bay,金是在斑岩成矿阶段引入的,在与阿比提比绿岩带南部大多数造山型金矿成矿同时发生的 ~2700 Ma 区域变形阶段,金既没有被重新移动,也没有被进一步引入。
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引用次数: 0
Detection and Interpretation of Central Type Structures within the Territory of Southeastern Transbaikalia for Prediction of Ore-Forming Systems 为预测成矿系统而探测和解释外贝加尔东南部地区的中心型结构
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s107570152460018x
S. A. Ustinov, V. A. Petrov, V. A. Minaev, I. O. Nafigin, E. V. Yarovaya

Abstract

Extremely little attention is paid to the issues of detecting and interpreting of central type structures (CTSs) when conducting remote structural-geological and structural-geomorphological studies. At the same time, in the 1970–1980s, it was proven that CTSs play an important role in the localization of deposits and ore fields. The position of these structures must necessarily be taken into account when solving problems of searching for and predicting mineral resources in the context of metallogenic analysis and reconstruction of the geological history of development of the studied areas. The almost complete absence of results of mass detection and interpreting of CTSs can be explained by the still poorly developed methodology for identifying and analyzing this type of structure. In the present study for the territory of Southeastern Transbaikalia, based on modern geoinformation technologies, the use of remote sensing data (radar topographic survey) of high resolution, the creation of a digital elevation model, and the application of an integrated structural-spatial analysis, an author’s approach to detection and interpretation of the CTSs is presented, including in connection with the localization of ore objects of various geological-industrial (geological-genetic) types within the framework of the concept of the formation of mineral systems. A statistical analysis of the CTSs identified in the area was carried out, which made it possible to establish a smooth increase in the number of structures with a decrease in their diameter. It is shown that the spatial maxima of ore mineralization extent within the territory are concentrated on the periphery of large CTSs and in their immediate vicinity. Most of the known large ore objects are confined to the internal areas of structures less than 10 km in diameter. Based on the approach of constructing model sections, it was possible to reconstruct the deep position of magma chambers associated with the identified CTSs, and, thereby, to determine the probable sources of metal-bearing fluids. A close spatial relationship between the identified magma chambers and deep faults has been established. To determine the most favorable sites for the deposition of ore mineralization, based on structural-spatial criteria, which include not only structural elements of the CTSs, but also segments of known fault structures, weight of evidence models of the territory have been created. The accuracy of the complex model is 89%. Thus, in accordance with the concept of mineral systems, the sources, migration pathways, and sites of the most probable deposition of ore mineralization have been reconstructed.

摘要 在进行远程构造地质学和构造地貌学研究时,对中心型构造(CTS)的探测和解释问题关注极少。与此同时,1970-1980 年代的研究证明,中心型构造在矿床和矿田的定位中发挥着重要作用。在冶金成因分析和重建所研究地区地质发展史的背景下,在解决寻找和预测矿产资源的问题时,必须考虑到这些结构的位置。由于识别和分析此类结构的方法尚不完善,因此几乎完全没有大规模探测和解释 CTS 的结果。在本项针对外贝加尔东南部地区的研究中,基于现代地理信息技术、高分辨率遥感数据(雷达地形测量)的使用、数字高程模型的创建,以及综合结构空间分析的应用,介绍了作者探测和解释 CTS 的方法,包括在矿产系统形成概念框架内各种地质-工业(地质-遗传)类型矿石的定位。通过对该地区已发现的岩浆岩进行统计分析,可以确定岩浆岩的数量在平稳增加,直径在逐渐减小。分析表明,境内矿石成矿范围的空间最大值集中在大型大陆架系统的外围及其邻近地区。大多数已知的大型矿体都局限于直径小于 10 公里的结构内部区域。根据构建模型剖面的方法,可以重建与已确定的岩浆岩站有关的岩浆室的深部位置,从而确定含金属流体的可能来源。已确定的岩浆室与深层断层之间存在密切的空间关系。为了根据结构空间标准(其中不仅包括岩浆层的结构元素,还包括已知断层结构的区段)确定矿化沉积的最有利地点,建立了该地区的证据权重模型。复合模型的准确率为 89%。因此,根据矿物系统的概念,重建了矿石成矿的来源、迁移路径和最可能的沉积地点。
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引用次数: 0
The First Results of a Study of Large Diamonds from Industrial Deposits of Yakutia 雅库特工业矿藏大型钻石研究的初步成果
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s1075701524600166
L. D. Bardukhinov, E. M. Sedykh, A. A. Evstratov, K. V. Garanin, N. N. Zinchuk

Abstract

A representative amount of diamonds larger than 10.8 carats extracted from deposits of Yakutia during separate ore processing of each kimberlite pipe has been studied for the first time. It is shown that, according to the diamond typomorphic characteristics of habit, nitrogen content, and aggregation, as well as hydrogen concentration in diamond, it is possible to carry out a preliminary evaluation of the deposit to predict the presence of large and giant diamonds. It has been established that large diamonds from the deposits of the Daldyn-Alakitsky area have wide variations of nitrogen impurity and its aggregations in comparison with diamonds from the Malobotuobinsky and Srednemarkhinsky areas. It is determined that the content of large diamonds in the pipes of Yakutia is inversely proportional to the number of rounded dodecahedroids. The most promising deposits for finding large diamonds are those in which the majority of diamonds belong to one population—average nitrogen low-aggregated diamonds that were formed at a temperature of ~1100°C. According to the study of geological collections of diamonds, it is shown that, in kimberlite pipes with an increased nitrogen content in diamonds, an increase in the proportion of large diamonds in the deposit is noted. On the contrary, according to the aggregation of nitrogen in diamonds, as a parameter of postgrowth history, there is a negative correlation with the content of large diamonds. An increased value of the concentrations of hydrogen in diamonds not only negatively affect the total diamond content of the deposit, but also generally control the decrease in the content of large diamonds.

摘要 首次研究了在雅库特矿床对每个金伯利岩管进行单独矿石加工时提取的大于 10.8 克拉的代表性金刚石。研究表明,根据金刚石的习性、含氮量、聚集度以及金刚石中氢浓度等金刚石类型学特征,可以对矿床进行初步评估,以预测大型和巨型金刚石的存在。已经确定,与马洛博图奥宾斯基和斯列德纳马克金斯基地区的钻石相比,达尔丁-阿拉基茨基地区矿藏中的大钻石在氮杂质及其聚集方面有很大差异。据测定,雅库特管道中大型钻石的含量与圆形十二面体的数量成反比。最有希望发现大型金刚石的矿藏是那些大部分金刚石属于一个群体--平均氮低聚集金刚石,在约 1100°C 的温度下形成的矿藏。对钻石地质藏品的研究表明,在金伯利岩管中,如果钻石的含氮量增加,矿床中大钻石的比例也会增加。相反,根据金刚石中氮的聚集情况,作为生长后历史的参数,与大粒金刚石的含量呈负相关。金刚石中氢浓度值的增加不仅会对矿床的总钻石含量产生负面影响,而且一般会控制大钻石含量的减少。
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引用次数: 0
Native Gold from Alluvial Sediments of the Kyvvozh Region and Its Possible Sources (Vol–Vym Uplift, Central Timan) 基伏沃日地区冲积沉积物中的原生金及其可能的来源(伏尔维姆隆起,中蒂曼地区)
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s1075701524600178
K. G. Parkhacheva, Yu. V. Glukhov, M. Yu. Sokerin, S. K. Kuznetsov, R. I. Shaibekov

Abstract

The most possible genetic types of primary sources are determined on the basis of study of typomorphic features of gold from alluvial sediments of the Kyvvozh region of Central Timan, including economic placers. The size of gold particles widely varies, reaching small nuggets; there are rounded, weakly rounded, and nonrounded particles. Many of them underwent recurrent deformations in form of envelope curves, pits, and fractures. Most gold grains have high-fineness rims. Native gold always contains Ag and, locally, Cu, Pd, and Hg. There are frequent blocky gold particles with high-Ag veinlet zones. Native gold is intergrown with and contains inclusions of pyrite and galena and rarely minerals of the cobaltite–gersdorffite series, ankerite, galenobismuthite, native bismuth, and aurostibite, as well as sudovikovite PtSe2, which is identified for the first time in the region. Three types of native gold are recognized: (1) homogenous Ag-bearing, (2) blocky with high-Ag veinlet zones, and (3) rare Ag-bearing with Cu and Pd. The morphology, composition, and structure of placer gold indicate its contribution from various (including proximal) sources. The NW-oriented zones of hydrothermal stringer-disseminated sulfide mineralization, which are partly exposed during placer exploitation, are most interesting. Native gold with Cu and Pd is most likely related to the derivatives of basic magmatism. The Vol–Vym, Tsil’ma, and Chetlas uplifts of Central Timan can be considered the promising for primary gold and deserve further study and searching works.

摘要 根据对中提曼省基辅沃日地区冲积沉积物(包括经济堆积物)中金的类型特征的研究,确定了原生矿源最可能的遗传类型。金颗粒的大小差异很大,甚至有小金块;有圆形、弱圆形和非圆形颗粒。其中许多颗粒经历了反复变形,形成了包络曲线、凹坑和裂缝。大多数金粒都有高细度的边缘。原生金总是含有银,局部还含有铜、钯和汞。经常出现块状金颗粒,并伴有高银细脉带。原生金与黄铁矿和方铅矿相互交错,并含有黄铁矿和方铅矿的包裹体,很少有钴铁矿-格斯多佛铁矿系列、黝帘石、方铋矿、原生铋、黝帘石,以及在该地区首次发现的苏多维可夫石 PtSe2。原生金有三种类型:(1) 均质含 Ag,(2) 块状含高金细脉带,(3) 含铜和钯的稀有含 Ag。块状金的形态、成分和结构表明它来自不同的(包括近端)来源。最令人感兴趣的是西北向热液串状浸蚀硫化物矿化带,这些矿化带在块金开采过程中部分暴露出来。含铜和钯的原生金很可能与碱性岩浆岩的衍生物有关。中提曼的沃尔维姆(Vol-Vym)、齐勒马(Tsil'ma)和切特拉斯(Chetlas)隆起带可被视为原生金的宝地,值得进一步研究和勘探。
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引用次数: 0
Hydrothermal–Metasomatic and Metamorphic Formations of the Olympiada Gold-Ore Deposit (Yenisei Ridge): New Data on Their Composition and Mineralogical, Petrographic, and Geochemical Features 奥林匹亚达金矿(叶尼塞山脊)的热液-成岩和变质构造:关于其成分以及矿物学、岩相学和地球化学特征的新数据
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-08-28 DOI: 10.1134/s1075701524700223
V. V. Shatov, S. V. Kashin, V. N. Belova, E. N. Afanasieva, V. A. Mikhailov

Abstract

The article presents the results of mineralogical, petrographic, and geochemical studies of hydrothermally altered and metamorphic formations of the Olympiada deposit. It shows that the combination of beresitization-sericitization aureoles, which control the distribution of stratiform gold–sulfide mineralization in space with multiplicative positive geochemical anomalies of AuAsTeSbHg composition close to them in morphology, can be used as hydrothermal alteration and geochemical criteria for predicting gold–sulfide mineralization in the Olympiada ore field. The geological and genetic model of the formation of the Olympiada ore deposit is discussed, and recommendations on the use of this model for prospecting purposes are given.

摘要 文章介绍了对奥林匹亚达矿床热液蚀变和变质地层进行矿物学、岩石学和地球化学研究的结果。研究表明,控制层状金-硫化物矿化在空间分布的beresitization-sericitization aureoles与形态上与之相近的AuAsTeSbHg成分的乘法正地球化学异常的组合,可作为预测奥林匹亚达矿区金-硫化物矿化的热液蚀变和地球化学标准。讨论了奥林匹亚达矿床形成的地质和遗传模型,并就将该模型用于探矿目的提出了建议。
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引用次数: 0
Pyrite Re–Os Geochronology of the Erlian Uranium District: an Alternative Dating Method for Sandstone-type Uranium Deposits 二连铀矿区黄铁矿 Re-Os 地球年代学:砂岩型铀矿床的另一种定年方法
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-07-18 DOI: 10.1134/s1075701523600081
C. Zhang, X. D. Li, C. H. Liu

Abstract

Owing to the lack of precise and reliable mineralization ages, the origins of some sandstone-type U deposits (STUDs) are still debated. The unusual texture of U ore (commonly uraninite) and the difference between the chemical characteristics of U and its radiogenic daughter isotopes make U–Pb dating unsuitable for STUDs. However, STUDs are commonly rich in Re; therefore, Re–Os dating may be an alternative. Re–Os dating of two groups of pyrite samples from U ores in the Erlian sandstone-type U district yields two similar ages: 52.5 ± 4.7 and 53.3 ± 3.5 Ma. These ages are consistent with previous U–Pb ages (56.5 ± 7.5 and 63 ± 22 Ma) and demonstrate the reliability of sulfide Re–Os dating of STUDs. The pyrite Re–Os ages suggest that the Erlian STUDs formed at ~53 Ma, corresponding to the regional uplift of the Erlian basin during the Late Cretaceous–Early Eocene and the humid environment in the region during the Early Eocene Climatic Optimum.

摘要由于缺乏精确可靠的成矿年龄,一些砂岩型铀矿床(STUDs)的成因仍存在争议。由于铀矿石(通常为铀矿石)的质地不同寻常,而且铀的化学特征与其放射性子同位素之间存在差异,因此铀-铅年代测定不适合砂岩型铀矿床。不过,STUD 通常富含 Re,因此,Re-Os 测定法可能是一个替代方法。对二连砂岩型铀矿区的两组黄铁矿样品进行 Re-Os 测定,得到了两个相似的年龄:52.5 ± 4.7 Ma 和 53.3 ± 3.5 Ma。这些年龄与之前的 U-Pb 年龄(56.5 ± 7.5 和 63 ± 22 Ma)一致,证明了 STUDs 的硫化物 Re-Os 测定的可靠性。黄铁矿 Re-Os 年龄表明,二连 STUDs 形成于 ~53 Ma,与晚白垩世-早始新世期间二连盆地的区域隆升以及早始新世气候最适宜期期间该地区的潮湿环境相对应。
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引用次数: 0
Unique Ore–Silicate Pegmatite of Monchepluton with High Contents of Ni, Cu, and PGE (Murmansk Region) 具有高镍、铜和 PGE 含量的 Monchepluton 独特矿硅酸盐伟晶岩(摩尔曼斯克地区)
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-07-18 DOI: 10.1134/s1075701524700065
D. A. Orsoev, V. F. Smolkin, A. S. Mekhonoshin
<h3 data-test="abstract-sub-heading">Abstract</h3><p>At the beginning of the 1960s, a large body of funnel-shaped ore pegmatite composed of Cu–Ni sulfide ores and a gabbronorite matrix was discovered at the Nittis–Kumuzhya–Travyanaya ore vein field of the Northern Chamber of Monchepluton (Kola Peninsula). In terms of its localization conditions, size, structure, and enrichment in sulfides and platinum-group elements (PGEs), it is a unique formation that has no analogues among other Paleoproterozoic layered complexes of the Fennoscandian Shield. Ore pegmatite occurs in the upper part of the layered zone of Mt. Nittis, which is composed of harzburgites and orthopyroxenites. Its horizontal size is 9 × 16 m, and the vertical one is 15 m. Three zones are distinguished in the structure of the body: I, a core of continuous sulfides; II, coarse- and giant-grained gabbronorites, enriched in interstitial sulfides; and III, a contact zone with sideronite sulfides with gradual transitions into host orthopyroxenites. Petro- and geochemical, mineralogical, and isotope studies of rocks and ores were performed using modern analysis methods. Ore pegmatite is most recent product in the processes of fractional crystallization of a magmatic melt, which derived as a large schlier with a sulfide core and a silicate matrix with a high concentration of fluids. The hypsometric level of the termination of the melt upwelling was determined by the equilibrium of the internal pressure of the volatiles and the external pressure of the overlying rocks. The δ<sup>18</sup>O values (+4.9…+6.1‰) are close to mantle marks (δ<sup>18</sup>O = +5.7‰) that correspond to basic igneous rocks. Early, late, and postmagmatic stages of mineral formation with a consistent increase in the role of fluid components (H<sub>2</sub>O, CO<sub>2</sub>, Cl, F) are distinguished in the formation history of the ore pegmatite. According to the results of calculations performed using various mineral geothermometers, the melt crystallization at the magmatic stage occurred in the range of ∼1100–900°C at a pressure of about 5 kbar. The separation (liquation) of the immiscible sulfide liquid began at temperatures of 1100–1000°C. As the temperature decreases, the main silicate minerals (clino- and orthopyroxenes, plagioclase) were first to crystallize. In the interstitial space between these minerals, residual melt and sulfide liquid enriched in PGEs, Au, Ag, and chalcophile elements (As, Sn, Sb, Te, Bi, Pb, Zn) accumulated. A late magmatic association (pargasite, magnesian hornblende and phlogopite) was formed from the residual melt. During the cooling of the sulfide liquid to a temperature of ∼1000°C and below, a copper-bearing monosulfide solid solution (<i>Mss</i>) is detached. As a result of its solid-phase transformations, pyrrhotite, pentlandite, and chalcopyrite were formed. An intermediate solid solution (<i>Iss</i>) was formed from the residual sulfide liquid, which was enriched with Cu and noble met
摘要 20 世纪 60 年代初,在 Monchepluton(科拉半岛)北腔的 Nittis-Kumuzhya-Travyanaya 矿脉区发现了一个由铜镍硫化矿石和榴辉岩基质组成的大型漏斗状矿伟晶岩体。就其定位条件、大小、结构以及硫化物和铂族元素(PGEs)的富集程度而言,它是一个独特的地层,在芬诺斯坎地盾的其他古新生代层状复合地层中没有类似的地层。矿伟晶岩位于尼蒂斯山层状带的上部,由哈兹堡岩和正长岩组成。矿体结构分为三个区域:I 区为连续硫化物核心区;II 区为粗粒和巨粒榴辉岩,富含间隙硫化物;III 区为菱铁矿硫化物接触区,逐渐过渡到主岩正长闪长岩。利用现代分析方法对岩石和矿石进行了岩石和地球化学、矿物学和同位素研究。矿石伟晶岩是岩浆熔体分块结晶过程中的最新产物,它衍生为具有硫化物核心和硅酸盐基质的大型片岩,并含有高浓度的流体。熔体上涌终止的湿度水平是由挥发物的内部压力和上覆岩石的外部压力的平衡决定的。δ18O值(+4.9...+6.1‰)接近地幔标志(δ18O = +5.7‰),与基本火成岩相对应。在矿伟晶岩的形成历史中,矿物形成的早期、晚期和岩浆后阶段,流体成分(H2O、CO2、Cl、F)的作用不断增加。根据使用各种矿物地热仪进行计算的结果,岩浆阶段的熔体结晶发生在 ∼1100-900°C 范围内,压力约为 5 千巴。不相溶硫化物液体的分离(液化)开始于 1100-1000°C 的温度。随着温度的降低,主要的硅酸盐矿物(类辉石和正长石、斜长石)首先结晶。在这些矿物之间的间隙空间中,富含 PGEs、Au、Ag 和亲铝元素(As、Sn、Sb、Te、Bi、Pb、Zn)的残余熔体和硫化物液体不断积累。残余熔体中形成了晚期岩浆组合(辉绿岩、镁质角闪石和辉绿岩)。在硫化物液体冷却到 ∼1000°C 及以下温度的过程中,一种含铜的单硫化物固溶体(Mss)脱离出来。由于其固相转变,形成了黄铁矿、辉铜矿和黄铜矿。残余的硫化物液体形成了中间固溶体(Iss),其中富含铜和贵金属。在低于 550°C 的温度下,该溶液先后分解成黄铜矿、黄铁矿和方解石。主要的 PGE 矿物有以下几种:michenerite PdBiTe、sobolevskite Pd(Bi,Te)、froodite PdBi2、merenskyite PdTe2 和 moncheite PtTe2。金和银矿物的代表矿物是电石(AuAg)和辉锑矿(Ag2Te)。还发现了一种罕见的矿物-铈镧矿(Ag4TeS)。伟晶岩矿石中的钯含量在百万分之 64.13-0.09 之间变化,铂含量在百万分之 2.70-0.004 之间变化。Monchepluton 的矿石潜力还远远没有开发完。因此,弄清矿伟晶岩成因的遗传特征及其与铜镍矿化的联系不仅具有岩石学意义,而且具有重要的现实意义,包括为 PGE-Cu-Ni 矿脉类型制定探矿指标。
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引用次数: 0
LA-ICP-MS Zircon U-Pb Dating of Permian Manganese Ores in Zunyi, Guizhou Province and Mineralization Age 贵州遵义二叠纪锰矿的 LA-ICP-MS 锆石 U-Pb 定年与成矿时代
IF 0.7 4区 地球科学 Q3 GEOLOGY Pub Date : 2024-07-18 DOI: 10.1134/s1075701524700089
Minkai Du, Zhichen Liu, Wengchao Yu, Yang Wang, Deng Chen, Lin Xiao, Liang Xiao

Abstract

The Middle Permian manganese deposit in Zunyi, northern Guizhou is one of the major manganese mining areas in South China. However, the age of this manganese deposit has not been accurately constrained. Previous studies have generally concluded that the formation of Zunyi manganese ores was linked with the early activities of the Emeishan Large Igneous Province (ELIP). In this study, we investigated the lithology and mineralization age of the Mn-bearing rocks in the study area and explored the connections between ELIP and the genesis of these rocks. Zircon samples from the Mn-bearing tuff in the Tuanxi section of Zunyi were used for zircon U-Pb chronological analysis by LA-ICP-MS method. The results constrain the deposition age of Mn-bearing rocks in Member 3 of the Maokou Formation was older than 266 ± 3 Ma, this age was closely related to the early stage of ELIP, but it was 5–10 Ma earlier than the main eruption of the Emeishan basalt. Combined with the regional paleogeography, we believe that the mantle plume activities prior to the main eruption of ELIP provided the tectonic stress, manganese source, and mineralization environment for manganese ore formation in the rift basin of the study area.

摘要 贵州北部遵义的中二叠统锰矿床是中国南方主要的锰矿区之一。然而,该锰矿床的年龄尚未得到准确测定。以往的研究普遍认为,遵义锰矿的形成与峨眉山大火成岩省(ELIP)的早期活动有关。在这项研究中,我们调查了研究区内含锰岩石的岩性和成矿时代,并探讨了峨眉山大火成岩带与这些岩石成因之间的联系。采用LA-ICP-MS方法对遵义团溪段含锰凝灰岩中的锆石样品进行了锆石U-Pb年代学分析。结果表明,茅口地层第三系含锰矿岩石的沉积年龄大于266±3Ma,该年龄与ELIP早期密切相关,但早于峨眉山玄武岩主喷发期5-10Ma。结合区域古地理,我们认为ELIP主喷发前的地幔羽流活动为研究区断裂盆地锰矿的形成提供了构造应力、锰源和成矿环境。
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引用次数: 0
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Geology of Ore Deposits
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