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Scheelite U–Pb dating constraints on the timing of the formation of the Zhazixi Sb-W deposit in South China 白钨矿U-Pb年代测定对华南寨子溪Sb-W矿床形成时间的制约
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-30 DOI: 10.1007/s00126-024-01249-4

Abstract

The Zhazixi deposit hosted in sedimentary rocks is a major Sb-W deposit in South China. The mineral scheelite, which can be dated by the U-Pb method, commonly occurs in both tungsten (W)-dominated and antimony (Sb)-dominated ore veins of the deposit. Cathodoluminescence (CL) images reveal the presence of three distinct stages of scheelite (Sch-I, Sch-II and Sch-III) within the deposit. These three scheelites were dated using in-situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), yielding U-Pb ages of 158.1±5.4 Ma and 157.6 ± 4.9 Ma for Sch-I, 155 ± 11 Ma for Sch-II, and 151.3±6.1 Ma for Sch-III. These data suggest that the Zhazixi Sb-W deposit formed during the Late Jurassic (160–150 Ma) rather than the Late Triassic as previously suggested. Considering the temporal similarity with low-temperature hydrothermal Sb deposits in the Xiangzhong metallogenic province (XZMP), the formation of the Sb-W deposit may have followed a similar genetic model, where meteoric groundwater circulated to depth and extracted metals from fertile basement rocks through fluid-rock interaction, resulting in the generation of ore fluids. This study highlights that Late Jurassic low-temperature hydrothermal Sb-polymetallic mineralization in the XZMP is likely more extensive than previously perceived.

摘要 沉积岩中的寨子溪矿床是中国南方的一个主要锑钨矿床。该矿床以钨(W)为主的矿脉和以锑(Sb)为主的矿脉中都普遍存在可采用U-Pb法测定年代的矿物白钨矿。阴极电致发光(CL)图像显示,矿床内存在三个不同阶段的白钨矿(Sch-I、Sch-II 和 Sch-III)。利用原位激光烧蚀-电感耦合等离子体质谱法(LA-ICP-MS)对这三种白钨矿进行了年代测定,得出 Sch-I 的 U-Pb 年龄分别为 158.1±5.4 Ma 和 157.6 ± 4.9 Ma,Sch-II 为 155 ± 11 Ma,Sch-III 为 151.3±6.1 Ma。这些数据表明,寨子溪铅锌矿床形成于晚侏罗世(160-150 Ma),而非之前认为的晚三叠世。考虑到与湘中成矿省(XZMP)低温热液Sb矿床在时间上的相似性,Sb-W矿床的形成可能遵循了类似的成因模式,即陨石地下水向深部循环,通过流体-岩石相互作用从肥沃的基底岩石中提取金属,从而产生矿石流体。这项研究突出表明,XZMP 中的晚侏罗世低温热液锑多金属矿化可能比以前认为的更为广泛。
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引用次数: 0
The magmatic origin of propylitic alteration of the Zhengguang epithermal Au-Zn deposit, Heilongjiang, China: evidence from mineral compositions and H–O-Sr isotopes 中国黑龙江正光热液型金锌矿床丙基蚀变的岩浆起源:矿物成分和 H-O-Sr 同位素证据
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-17 DOI: 10.1007/s00126-023-01243-2
Le Wang, Ming-Jian Cao, Shen Gao, Massimo Chiaradia, Pete Hollings, Ke-Zhang Qin, Xin-Yu Zou, Guo-Xue Song, Xu-Yong Pang, Guang-Ming Li

The origin of propylitic fluids in intermediate sulfidation mineralization has not been investigated in detail. Here, we present an extensive petrographic, geochemical, and isotopic (O-H-Sr) study of propylitic epidote, chlorite, and calcite from the Zhengguang intermediate sulfidation epithermal Au-Zn deposit, NE China. Propylitic minerals can be divided into three main types based on their different textural occurrences, namely interstitial cement of clasts of hydrothermal breccia, replacement of primary plagioclase or hornblende, and vein infill of cracks, with late, minor calcite as amygdules in vesicles of andesite representing a fourth textural occurrence. The H-O isotope compositions and mass balance calculations suggest that most propylitic epidote records a dominant (> 50%) contribution of magmatic fluids. The decrease of the average δ18({mathrm O}_{{mathrm H}_2mathrm O};)values equilibrated with different types of epidote (cement 6.8 ± 0.7‰, replacement 5.1 ± 1.1‰, vein 4.5 ± 1.4‰, 1 SD), and the decreasing content of high-temperature elements (e.g., Cu-Mo) from cement, through replacement to vein epidote and chlorite, collectively indicates a decreasing role of magmatic fluids. Replacement epidote and chlorite are enriched in Sr-Mn-Y-Sb, whereas replacement epidote and calcite record similar (87Sr/86Sr)i values to the andesitic host rock, suggesting that replacement minerals inherit certain elements from plagioclase and hornblende, and the Sr isotope signature of the wall rocks. We highlight that propylitic alteration in epithermal deposits can involve significant proportions of magmatic fluids and texturally different alteration mineral types should be considered when using mineral isotopic or chemical compositions to track fluid sources or to vector towards the location of intrusive centers.

关于中间硫化成矿过程中丙基流体的来源,还没有进行过详细的研究。在此,我们对中国东北正光中级硫化表生金锌矿床中的丙闪石、绿泥石和方解石进行了广泛的岩石学、地球化学和同位素(O-H-Sr)研究。丙闪石矿物可根据其不同的质地特征分为三大类,即热液角砾岩碎屑的间隙胶结物、原生斜长石或角闪石的置换物以及裂隙的矿脉填充物,第四种质地特征是安山岩囊泡中的晚期小方解石。H-O同位素组成和质量平衡计算表明,大多数丙闪石记录了岩浆流体的主要贡献(50%)。平均δ18({mathrm O}_{mathrm H}_2mathrm O};)值的下降与不同类型的表土(胶结物 6.8 ± 0.7‰,置换物 5.1 ± 1.1‰,脉石 4.5 ± 1.4‰,1 SD)的平衡以及高温元素含量的下降(例如、从胶结物到脉石和绿泥石的置换,以及高温元素(如铜钼元素)含量的减少,共同表明岩浆流体的作用正在减弱。置换表长石和绿泥石富含Sr-Mn-Y-Sb,而置换表长石和方解石的(87Sr/86Sr)i值与安山质主岩相似,这表明置换矿物继承了斜长石和角闪石中的某些元素,以及岩壁岩石的Sr同位素特征。我们强调,热液矿床中的丙基蚀变可能涉及相当比例的岩浆流体,在利用矿物同位素或化学成分追踪流体来源或矢量确定侵入中心位置时,应考虑质地不同的蚀变矿物类型。
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引用次数: 0
Mechanism of germanium enrichment in the world-class Huize MVT Pb–Zn deposit, southwestern China 中国西南部世界级会泽 MVT 铅锌矿床的锗富集机制
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-13 DOI: 10.1007/s00126-023-01242-3
Pan-Pan Niu, Manuel Muñoz, Olivier Mathon, Suo-Fei Xiong, Shao-Yong Jiang

The world-class Huize deposit hosts significant germanium (Ge) resources in the Sichuan–Yunan–Guizhou (SYG) Mississippi Valley-type (MVT) Pb–Zn province of China. The distribution and enrichment mechanism of Ge is still poorly understood. In the main ore-forming stage of Huize, we identified six sphalerite colors from C1 (black) to C6 (white) in transmitted light. Two color sequences are confirmed, including C1 → C2 → C3 → C6 and C1 → C2 → C4 → C5 → C6. We used multiple analytical methods to reveal the Ge distribution and incorporation mechanism into sphalerite and the possible enrichment factors. Our results show that Ge occurs as argutite (GeO2), and in the sphalerite crystal lattice, C1 and C3 sphalerite has up to 593 ppm Ge. Two substitution mechanisms, i.e., Ge4+ + □(vacancy) → 2Zn2+ (e.g., C1 and C2) and Ge4+ + 2Cu+ → 3Zn2+ (e.g., C2, C3, C4, and C5), are inferred from the Huize sphalerite. They show different spatial structures of sphalerite and a weak shift of the white line observed by high-resolution X-ray absorption near-edge structure (XANES) spectroscopy. The trace-element composition of sphalerite suggests that reduced sulfur content of the ore-forming fluid contributes to Ge enrichment, followed by high temperature (> 300 °C).

世界级的会泽矿床位于中国川滇黔(SYG)密西西比河谷型(MVT)铅锌矿省,蕴藏着大量的锗(Ge)资源。人们对 Ge 的分布和富集机制还知之甚少。在会泽的主要成矿阶段,我们在透射光下发现了从 C1(黑色)到 C6(白色)的六种闪锌矿颜色。确认了两个颜色序列,包括 C1 → C2 → C3 → C6 和 C1 → C2 → C4 → C5 → C6。我们采用多种分析方法揭示了闪锌矿中 Ge 的分布和掺入机制以及可能的富集因素。结果表明,Ge 以方铅矿(GeO2)的形式存在,在闪锌矿晶格中,C1 和 C3 闪锌矿的 Ge 含量高达 593 ppm。从会泽闪锌矿中推断出两种置换机制,即 Ge4+ + □(空缺)→2Zn2+(如 C1 和 C2)和 Ge4+ + 2Cu+ →3Zn2+(如 C2、C3、C4 和 C5)。它们显示了闪锌矿不同的空间结构,以及高分辨率 X 射线吸收近边结构(XANES)光谱观察到的白线的微弱偏移。闪锌矿的痕量元素组成表明,成矿流体中硫含量的降低促成了锗的富集,而高温(300 °C)则是其次。
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引用次数: 0
Geochemistry and Sm─Nd─Fe─Si isotope compositions as insights into the deposition of the late Neoarchean Qidashan banded iron formation, North China Craton 地球化学和 Sm─Nd─Fe─Si 同位素组成对华北克拉通新元古代晚期齐大山带状铁矿沉积的启示
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-09 DOI: 10.1007/s00126-024-01245-8
Changle Wang, Zidong Peng, Xiaoxue Tong, Liang Gao, Lianchang Zhang

Banded iron formations (BIFs) are chemical sediments that reflect the composition of the seawater from which they were deposited. Therefore, they provide a key part of the evidence for the modern scientific understanding of paleoenvironmental conditions in Archean and Paleoproterozoic times. Although BIFs have been extensively studied, many aspects (e.g., specific mechanisms controlling iron (Fe) and silicon (Si) precipitations) of their origin still remain enigmatic because of the lack of modern analogues. In China, abundant BIFs occur throughout within the late Neoarchean volcanic and sedimentary succession and therefore are the principal source of Fe for the Chinese steel industry. Here, we examine the ~ 2.53 Ga Qidashan BIF, one of the most extensive BIFs in China, by conducting a detailed petrographic and multi-proxy investigation to well constrain its formation mechanism. The BIF consists mainly of magnetite and quartz with lesser amounts of calcite and various types of silicate minerals, of which the content of Al-rich minerals (i.e., chlorite) is rare, coupled with a low abundance of detrital geochemical indicators (e.g., Al and Ti), suggesting that the BIF is relatively pure with insignificant terrigenous contamination. A wide range of Nd isotope compositions and shale-normalized patterns and specific anomalies of rare earth elements, especially highly positive Eu anomalies, indicate that the BIF precipitated from seawater imprinted by high-temperature hydrothermal fluids. Furthermore, there is a significantly negative correlation between Nd isotope values and total Fe contents of the BIF. This suggests that such enhanced hydrothermal activity provided vast volumes of dissolved Fe(II) necessary for the formation of the BIF via alteration of ancient continental crust. In addition, the Qidashan BIF was deposited under pervasively anoxic conditions, as revealed by the absence of shale-normalized Ce anomalies and the presence of consistently positive Fe isotope values. Hence, anoxygenic photosynthesis is the most plausible mechanism responsible for Fe(II) oxidation. Given that Fe─Si bonding has a strong impact on Si isotope fractionation, the formation of primary Fe(III) oxyhydroxides should have exerted a first-order control on the negative Si isotope signatures observed in the studied BIF samples. It is also noted that the BIF possesses a variation of negative Si isotope values, further implying that diagenetic dissolution and reprecipitation of silica took place after primary Si precipitation associated with Fe.

带状铁地层(BIFs)是一种化学沉积物,反映了沉积时海水的成分。因此,它们为现代科学了解阿新世和古近代的古环境条件提供了重要证据。尽管对 BIFs 进行了广泛的研究,但由于缺乏现代类似物,其起源的许多方面(如控制铁(Fe)和硅(Si)沉淀的具体机制)仍然是个谜。在中国,新元古代晚期的火山岩和沉积岩演替中遍布着丰富的 BIFs,因此它们是中国钢铁工业的主要铁元素来源。在此,我们通过详细的岩石学和多代理研究,对中国范围最广的BIF之一--约2.53 Ga的齐大山BIF进行了研究,以充分确定其形成机制。该BIF主要由磁铁矿和石英组成,含有少量方解石和各种硅酸盐矿物,其中富铝矿物(如绿泥石)含量稀少,且碎屑地球化学指标(如Al和Ti)含量较低,表明该BIF较为纯净,土著污染不明显。广泛的钕同位素组成和页岩归一化模式以及稀土元素的特定异常,特别是高正 Eu 异常,表明 BIF 是由高温热液注入的海水沉淀而成。此外,BIF 的钕同位素值与总铁含量之间存在明显的负相关。这表明,这种增强的热液活动提供了大量溶解的铁(II),这是通过改变古大陆地壳形成 BIF 所必需的。此外,齐大山 BIF 是在普遍缺氧的条件下沉积的,这一点从页岩归一化 Ce 异常值的缺失和铁同位素值持续为正值可以看出。因此,缺氧光合作用是造成铁(II)氧化的最合理机制。鉴于 Fe─Si 键对 Si 同位素分馏有很大影响,原生 Fe(III)氧氢氧化物的形成应该对在所研究的 BIF 样品中观察到的负 Si 同位素特征有一阶控制作用。我们还注意到,BIF 具有负硅同位素值的变化,这进一步表明,在与铁有关的原生硅沉淀之后,硅发生了成岩溶解和再沉淀。
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引用次数: 0
The Boring Billion: A key to resolving controversy on ore-fluid source models for orogenic gold deposits? Boring Billion:解决造山型金矿床矿石流体源模型争议的关键?
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-06 DOI: 10.1007/s00126-023-01244-1
David I. Groves, M. Santosh, Qingfei Wang, Liang Zhang, Hesen Zhao

Orogenic gold systems are arguably the most variable mineral system globally in terms of an extreme range of depositional depths, corresponding P–T conditions and wallrock alteration assemblages, structural controls and styles, and element associations. This diversity has ignited controversy on genetic models for the two decades since orogenic gold became a widely accepted term. From the diverse genetic models proposed, the two groups of fluid-source models that meet most genetic constraints are the following: (1) deposition from crustal fluids via metamorphic devolatilization at the amphibolite-greenschist transition, or potentially even deeper under specific tectonic conditions, and (2) deposition from sub-crustal fluids either by direct devolatilization of subducted oceanic crust and overlying sediment wedge or of previously metasomatized and fertilized mantle lithosphere. Both models normally postulate gold deposition within a geodynamic system that evolves from extension through compression into syn-gold transpression. Crustal metamorphic models normally invoke subduction-driven geodynamic systems that involve advection of crustal metamorphic fluids up crustal-scale faults. In contrast, sub-crustal devolatilization models involve subduction-related processes as both geodynamic drivers and gold sources with fault-controlled fluid conduits extending to below the Moho. The overall lack of orogenic gold and other subduction-related mineral systems during the unique Boring Billion (1.8–0.8 Ga) period provides an important constraint on this genetic debate. Boring Billion orogens had varying geodynamic drivers, asthenosphere upwelling, and low-P metamorphic terranes with crustal-scale faults, all parameters consistent with formation of orogenic gold systems, during subduction-independent accordion-type tectonics. The absence of orogenic gold during the Boring Billion provides critical evidence against the crustal metamorphic model and furthers the sub-crustal model which requires subduction as both the geodynamic driver and auriferous fluid source.

就沉积深度、相应的 P-T 条件和壁岩蚀变组合、结构控制和风格以及元素关联的极端范围而言,造山金系统可以说是全球变化最大的矿物系统。在成因金成为一个被广泛接受的术语后的二十年里,这种多样性引发了对成因模型的争议。在提出的各种成因模型中,符合大多数成因约束条件的流体源模型有以下两类:(1) 地壳流体在闪长岩-绿泥石转变期通过变质脱溶沉积,或在特定构造条件下可能在更深的地方沉积;(2) 地壳下流体通过俯冲洋壳和上覆沉积楔的直接脱溶沉积,或通过先前变质和肥化的地幔岩石圈沉积。这两种模式通常都假定金沉积在一个地球动力系统中,该系统由延伸通过压缩演变为同步金换位。地壳变质模型通常采用俯冲驱动的地球动力系统,涉及地壳变质流体沿地壳尺度断层的平流。与此相反,壳下脱熔模型涉及与俯冲有关的过程,既是地球动力驱动因素,也是金源,由断层控制的流体通道延伸到莫霍面以下。在独特的 Boring Billion(1.8-0.8 Ga)时期,总体上缺乏造山金矿和其他与俯冲相关的矿物系统,这为这一成因争论提供了重要的制约因素。Boring Billion时期的造山运动具有不同的地球动力驱动因素、星体上涌和具有地壳尺度断层的低P变质地层,所有这些参数都与独立于俯冲作用的风琴型构造期间造山金系统的形成相一致。博林千亿国际娱乐不存在造山型金矿,这为地壳变质模型提供了关键证据,并推进了亚地壳模型,该模型要求俯冲既是地球动力驱动因素,又是含金流体来源。
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引用次数: 0
Lithospheric hydrous pyroxenites control localisation and Ni endowment of magmatic sulfide deposits 岩石圈含水辉石控制岩浆硫化物矿床的定位和镍禀赋
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-01-04 DOI: 10.1007/s00126-023-01238-z
Isra S. Ezad, Daryl E. Blanks, Stephen F. Foley, David A. Holwell, Jason Bennett, Marco L. Fiorentini

Magmatic Ni–sulfide ore deposits are generally associated with basaltic to komatiitic igneous rocks that originate by partial melting of the mantle, which is usually modelled as a uniform four-phase peridotite. Existing models accept that the key metal contributors to mantle melts are olivine (Ni) and sulfide (Cu, platinum group elements (PGEs) and minor Ni). However, melting in the mantle commonly begins in volumetrically minor mantle assemblages such as hydrous pyroxenites that occur as veins in the peridotite mantle, which are rich in the hydrous minerals phlogopite, amphibole and apatite. The contribution of hydrous pyroxenites to the metal endowment of mantle melts may have been underestimated or overlooked in the past, partly because evidence of their input is partially erased as melting intensifies to involve peridotite.

Here, we compile new results from experiments and natural rocks which demonstrate that the hydrous minerals such as phlogopite, amphiboles and apatite all have high partition coefficients for Ni (3–20) and may be important repositories for Ni in mantle sources of igneous rocks. This implies that hydrous minerals hosted in metasomatic mantle lithologies such as hydrous pyroxenites may be important contributors to some magmatic Ni–sulfide ore systems. Hydrous pyroxenites contain hydrous minerals in large modal abundances up to 30–40 vol% in addition to clinopyroxene and a few vol% of oxide phases, such as rutile and ilmenite. These mantle lithologies are commonly associated with cratonic and continental regions, where low-temperature, low-degree volatile-rich melts commonly modify lithospheric peridotite mantle, depositing variable hydrous pyroxenites.

The lower melting temperatures of hydrous minerals in hydrous pyroxenite lithologies also means that the generation of magmatic ore deposits may not require a major thermal perturbation such as a plume, as the melting temperatures of hydrous pyroxenites lie around 300–350 °C lower than dry peridotites. Partial melts of hydrous pyroxenite are more voluminous at low temperatures than melts of peridotite would be. Furthermore, it is argued in the following that they would contain similar or even higher concentrations of Ni. Thus, predictive exploration models should consider domains of the lithospheric mantle where hydrous pyroxenites may be localised and concentrated, as they may have been episodically melted throughout the long-lived geological evolution of cratonic blocks, yielding Ni-rich melts that may be hosted in conduits of varying size and geometry at various crustal levels.

岩浆硫化镍矿床通常与玄武岩至柯麦饭石火成岩有关,这些火成岩起源于地幔的部分熔融,地幔通常被模拟为均匀的四相橄榄岩。现有模型认为,地幔熔体的主要金属成分是橄榄石(镍)和硫化物(铜、铂族元素和少量镍)。然而,地幔熔融通常是从体积较小的地幔组合开始的,如在橄榄岩地幔中以脉石形式出现的水合辉石,其中富含水合矿物辉石、闪石和磷灰石。过去,人们可能低估或忽视了含水辉石对地幔熔体金属禀赋的贡献,部分原因是随着熔化加剧,涉及橄榄岩时,含水辉石的贡献证据被部分抹去。在这里,我们汇编了来自实验和天然岩石的新结果,证明辉石、闪石和磷灰石等含水矿物对镍的分配系数都很高(3-20),可能是火成岩地幔源中镍的重要储存库。这意味着,寄存在水相辉长岩等变质地幔岩性中的含水矿物可能是某些岩浆硫化镍矿系统的重要成分。水相辉石中含有大量的水相矿物,其模态丰度高达 30-40 Vol%,此外还有烊辉石和少量 Vol%的氧化物相,如金红石和钛铁矿。这些地幔岩性通常与板块和大陆地区有关,在这些地区,低温、低度富挥发性熔体通常会改变岩石圈橄榄岩地幔,沉积出可变的含水辉石。水合辉绿岩岩性中水合矿物的熔融温度较低,这也意味着岩浆矿床的生成可能不需要羽流等重大热扰动,因为水合辉绿岩的熔融温度比干橄榄岩低约 300-350 ℃。水合辉绿岩的部分熔体在低温下比橄榄岩熔体的体积更大。此外,下文将论证它们含有类似甚至更高浓度的镍。因此,预测性勘探模型应考虑岩石圈地幔中水合辉长岩可能局部集中的区域,因为在板块漫长的地质演化过程中,水合辉长岩可能偶尔被熔化,产生富含镍的熔体,这些熔体可能存在于地壳各层不同大小和几何形状的导管中。
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引用次数: 0
Hydrothermal monazite and xenotime chemistry as genetic discriminators for intrusion-related and orogenic gold deposits: implications for an orogenic origin of the Pogo gold deposit, Alaska 热液独居石和氙化学作为侵入型金矿床和造山型金矿床的遗传判别因素:对阿拉斯加波戈金矿床造山起源的影响
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-12-29 DOI: 10.1007/s00126-023-01240-5
Ryan D. Taylor, Garth E. Graham, Heather A. Lowers

Attempts to geochemically distinguish between metamorphic-hydrothermal systems that form orogenic gold deposits and both reduced and oxidized magmatic-hydrothermal systems using isotopes or metal associations have proven ambiguous, particularly for orogenic gold and reduced intrusion-related gold systems. The absence of conclusive geochemical discriminators and the overlap in geologic characteristics have led to gold deposit models being potentially incorrectly applied, which in turn negatively affect regional mineral exploration and mine planning. In this study, in situ electron microprobe geochemical analyses of hydrothermal monazite and xenotime crystals associated with different types of gold-bearing deposits are shown to be effective geochemical discriminators. There are notable differences in mineral chemistry such as rare earth element (REE) profiles, total light REE, Dy, Er, Pr, Y, Nd/Sm, and La/Sm that distinguish monazite precipitated from metamorphic-hydrothermal fluids that form orogenic gold deposits and those precipitated from magmatic-hydrothermal fluids that form both porphyry Cu-Mo-Au and reduced intrusion-related gold deposits. Notable differences in overall xenotime abundances and concentrations of heavy REEs, Ca, and Sc are distinctive between the different deposit classes for xenotime. The origin of the controversially classified Pogo gold deposit, Tintina gold province, Alaska, which has been characterized as both a reduced intrusion-related and an orogenic gold deposit, is tested based upon the noted chemical differences associated with these hydrothermal phosphates. The findings of this study have implications for exploration and mine development in the Tintina gold province and other areas that contain deposits that are controversially classified as either orogenic or as magmatic-hydrothermal gold deposits.

事实证明,利用同位素或金属关联从地球化学角度区分形成造山型金矿床的变质热液系统与还原型和氧化型岩浆热液系统的尝试并不明确,尤其是对于造山型金矿和与还原侵入有关的金矿系统。由于缺乏确凿的地球化学判别指标以及地质特征的重叠,金矿床模型有可能被错误地应用,进而对区域矿产勘探和矿山规划产生负面影响。在本研究中,对与不同类型含金矿床相关的热液独居石和氙晶进行的原位电子微探针地球化学分析表明,它们是有效的地球化学判别指标。稀土元素(REE)剖面、轻稀土元素总量、Dy、Er、Pr、Y、Nd/Sm 和 La/Sm 等矿物化学成分存在明显差异,可区分形成造山型金矿床的变质热液沉淀的独居石,以及形成斑岩型铜-钼-金矿床和还原侵入型金矿床的岩浆热液沉淀的独居石。不同矿床类别的氙丰度和重稀土元素、钙和钪的浓度存在明显差异。根据与这些热液磷酸盐相关的化学差异,对阿拉斯加廷廷纳金矿区波戈金矿床的起源进行了测试,该矿床既被定性为与侵入有关的还原金矿床,也被定性为造山金矿床。这项研究的结果对 Tintina 金省和其他地区的勘探和矿山开发具有重要意义,这些地区的矿床被有争议地归类为造山型金矿床或岩浆热液型金矿床。
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引用次数: 0
Silver isotope analysis and systematics of native gold from the Rajapalot Co-enriched gold deposit, Finnish Lapland 芬兰拉普兰拉贾帕洛特共富集金矿床原生金的银同位素分析和系统学研究
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-12-21 DOI: 10.1007/s00126-023-01239-y
J. Tepsell, Y. Lahaye, F. Molnár, O.T. Rämö, N. Cook

Silver is probably the closest isotopic proxy to track monoisotopic gold and has been shown to have great potential to yield new information on the origin and enrichment processes of gold. This study describes the development of a tailored analytical protocol for accurate analysis of Ag isotopes and provides the first Ag isotope data for the Paleoproterozoic Rajapalot Au-Co deposit, Finnish Lapland. Six native Au samples yield ε109Ag values (relative to NIST SRM 978a) from −6.8 to +2.1 and are within the range of Ag isotopic compositions reported for native Au samples. The mean of the analyzed Au samples is ε109Ag = −3.8 ± 1.7 (2SD) with most of the samples with negative ε109Ag values (−6.7 to −2.0); one sample has a positive ε109Ag value of +2.1 ± 0.5. Silver isotope fractionation in the Rajapalot Au deposit was likely associated with physicochemical processes related to deposition and/or re-mobilization of the ore rather than with source region inheritance. It is suggested that redox reactions involving Ag+ ↔ Ag0 phase change primarily account for the isotopic differences within the deposit. Our results also suggest that the Rajapalot Au-Co deposit was formed via multistage ore-forming processes and/or that the primary ore was re-mobilized, which caused isotope fractionation along fluid pathways. Silver isotope variation within a deposit may mark a fractional crystallization trend with the lightest isotopic composition representing the earliest precipitate. Hence, Ag isotopes show potential as an isotopic vectoring tool in search of Au-enriched domains.

银可能是追踪单异位金的最接近的同位素替代物,并已被证明具有巨大的潜力,可以提供有关金的起源和富集过程的新信息。本研究介绍了为精确分析银同位素而开发的定制分析方案,并提供了芬兰拉普兰地区古生代拉贾帕洛特金-铜矿床的首个银同位素数据。六个原生金样品的ε109Ag值(相对于NIST SRM 978a)从-6.8到+2.1不等,在已报道的原生金样品的Ag同位素组成范围内。分析的金样品的平均值为 ε109Ag = -3.8 ± 1.7 (2SD),大多数样品的 ε109Ag 值为负值(-6.7 至 -2.0);一个样品的 ε109Ag 值为正值 +2.1 ± 0.5。拉贾帕洛特金矿床的银同位素分馏可能与矿石沉积和/或再移动的物理化学过程有关,而不是与矿源区的继承有关。我们认为,涉及 Ag+ ↔ Ag0 相变的氧化还原反应是造成矿床内同位素差异的主要原因。我们的研究结果还表明,拉贾帕洛特金-钴矿床是通过多级成矿过程形成的,并且/或者原生矿石被重新移动,这导致了流体路径上的同位素分馏。矿床内银同位素的变化可能标志着分馏结晶的趋势,最浅的同位素成分代表最早的沉淀物。因此,银同位素显示出作为同位素矢量工具寻找富金矿域的潜力。
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引用次数: 0
Correction to: The petrogenesis of highly fractionated gem‑bearing pegmatites of Malawi: evidence from mica and tourmaline chemistry and finite step trace element modelling 更正:马拉维高分馏含宝石伟晶岩的成岩作用:来自云母和电气石化学以及有限步微量元素建模的证据
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-12-19 DOI: 10.1007/s00126-023-01241-4
Tuhin Chakraborty, Steffen H. Büttner, Gelu Costin, Charles F. Kankuzi
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引用次数: 0
Evolution of the magmatic-hydrothermal system at the Erdenetiin Ovoo porphyry Cu-Mo deposit, Mongolia: constraints on the relative timing of alteration and mineralization 蒙古 Erdenetiin Ovoo 斑岩铜-钼矿床岩浆-热液系统的演变:蚀变和成矿相对时间的制约因素
IF 4.8 2区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-12-19 DOI: 10.1007/s00126-023-01221-8
Thomas Monecke, T. James Reynolds, Tsolmon Gonchig, Natsagdorj Batbayar

The evolution of the magmatic-hydrothermal system that formed the Triassic Erdenetiin Ovoo porphyry Cu-Mo deposit, northern Mongolia, is reconstructed through the study of the sequence of stockwork veining and the petrographic characteristics of the veins, as well as the cathodoluminescence and fluid inclusion characteristics of the vein quartz. Early A veins associated with potassic alteration formed at temperatures ≳ 500 °C under lithostatic pressures. The quartz in these veins shows a blue cathodoluminescence emission and is extensively recrystallized. Subhedral to euhedral quartz crystals contained in AB veins precipitated at the ductile to brittle transition at ~ 400–450 °C. The quartz crystals have cores showing a long-lived purple cathodoluminescence color with well-developed growth zoning, whereas the rims of the crystals lack growth banding and have a brownish-red cathodoluminescence emission. Fluid inclusions in the A and AB veins show elevated CO2 concentrations but show no evidence for immiscibility, implying that Erdenetiin Ovoo formed at ≳ 5 km below paleosurface. Quartz in the A and AB veins is crosscut by molybdenite ribbons. The presence of encapsulated molybdenite and sericite grains along growth zones in the quartz rims of the subhedral to euhedral quartz crystals constrains the timing of Mo introduction and suggests an association with the sericite alteration of the host rocks, which affected 50–60% of the deposit. Elevated Cu grades at Erdenetiin Ovoo are linked to the occurrence of C veins, which consist primarily of chalcopyrite and pyrite. These veins surrounded by halos of sericite-chlorite alteration lack quartz as a gangue mineral, suggesting formation at conditions of retrograde quartz solubility at ~ 400 °C and hydrostatic pressures. Late D veins formed at ≲ 375 °C and hydrostatic conditions. The veins consist primarily of pyrite and are associated with texturally destructive sericite alteration of the host rocks. The study demonstrates that hypogene Cu mineralization at Erdenetiin Ovoo was predated and post-dated by sericite alteration, which has important implications to alteration vectoring in porphyry exploration worldwide.

通过对岩浆脉序和岩脉的岩相特征以及岩脉石英的阴极发光和流体包裹体特征的研究,重建了形成蒙古北部三叠纪额尔德尼铁林敖包斑岩铜-钼矿床的岩浆-热液系统的演化过程。与钾盐蚀变有关的早期A型矿脉是在岩石压力下温度≳ 500 °C时形成的。这些矿脉中的石英发出蓝色阴极荧光,并广泛重结晶。AB 矿脉中所含的亚方体到八面体石英晶体是在约 400-450 °C 的韧性到脆性转变过程中析出的。石英晶体的内核显示出长效的紫色阴极荧光,并具有发达的生长带状,而晶体的边缘则缺乏生长带状,并发出棕红色的阴极荧光。A 和 AB 矿脉中的流体包裹体显示二氧化碳浓度升高,但没有显示出不溶解的迹象,这意味着额尔德尼敖包岩是在≳ 5 千米的古地表以下形成的。A 和 AB 矿脉中的石英被辉钼矿带横切。亚方体至八面体石英晶体的石英边缘生长带中存在包裹的辉钼矿和绢云母晶粒,这限制了钼的引入时间,并表明与寄主岩的绢云母蚀变有关,该蚀变影响了 50-60% 的矿床。Erdenetiin Ovoo 铜品位的升高与主要由黄铜矿和黄铁矿组成的 C 矿脉的出现有关。这些被绢云母-绿泥石蚀变晕所包围的矿脉中没有石英这种煤矸石矿物,这表明矿脉是在约 400 °C 的逆行石英溶解度和静水压力条件下形成的。晚期 D 型矿脉是在≲ 375 °C和静水压力条件下形成的。这些矿脉主要由黄铁矿组成,与母岩的纹理破坏性绢云母蚀变有关。该研究表明,绢云母蚀变在 Erdenetiin Ovoo 的下伏铜矿化之前和之后都曾出现过,这对全球斑岩勘探中的蚀变矢量具有重要意义。
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引用次数: 0
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