The metallogenic environment of the Dounan manganese deposit,Southeast Yunnan,China: evidence from geochemistry and Mössbauer spectroscopic

Acta Geochimica - The Dounan manganese deposit is a typical large-scale marine sedimentary manganese deposit of the Middle Triassic in China. The metallogenic environment and change process...     

Contributions from mafic alkaline magmas to the Bingham porphyry Cu–Au–Mo deposit, Utah, USA

The Bingham porphyry Cu-Au-Mo deposit, Utah, may only be world-class because of substantial contributions of sulfur and metals from mafic alkaline magma to an otherwise unremarkable calc-alkaline system. Volcanic mafic alkaline rocks in the district are enriched in Cr, Ni, and Ba as well as Cu, Au, platinum group elements (PGE), and S. The bulk of the volcanic section that is co-magmatic with ore-related porphyries is dacitic to trachytic in composition, but has inherited the geochemical signature of high Cr, Ni, and Ba from magma mixing with the mafic alkaline rocks. The volcanic section that most closely correlates in time with ore-related porphyries is very heterogeneous containing clasts of scoriaceous latite, latitic, and minette, and flows of melanephelinite, shoshonite, and olivine latite in addition to volumetrically dominant dacite/trachyte. Bingham ore-related porphyries show ample evidence of prior mixing with mafic alkaline magmas. Intrusive porphyries that have not been previously well-studied have several chemical and mineralogical indications of magma mixing. These "mixed" lithologies include the hybrid quartz monzonite porphyry, biotite porphyry, and minette dikes. Even some of the more silicic latite and monzonite porphyries retain high Cr and Ba contents indicative of mixing and contain trace amounts of sapphire (<1 mm). The heterogeneous block and ash flow deposits also contain sapphire and are permissively correlated with the intrusions based on chemical, mineralogical, and isotopic data. Magma mixing calculations suggest about 10% of the monzonitic/latitic ore-related magma may have been derived from mafic alkaline magma similar to the melanephelinite. If the original S content of the mafic magma was about 2,000-4,000 ppm, comparable with similar magmas, then the mafic magma may have been responsible for contributing more than half of the S and a significant portion of the Cu, Au, and PGE in the Bingham deposit.     

Ichnological evidence of marine incursions in the lacustrine–palustrine Bembridge Limestone Formation (Eocene), Isle of Wight,southern England

Trace fossils are described from the Eocene Bembridge Limestone Formation from the Isle of Wight and used to constrain the paleoenvironmental interpretation. The lacustrine–palustrine succession contains three limestone beds, which are separated by clay and marl. The middle and upper limestone beds reveal complex burrow systems developed at their top. Based on their characteristics, these burrow systems are assigned to the ichnotaxon Balanoglossites triadicus Mägdefrau, which is associated with the shallow superficial grooves Sulcolithos variabilis Knaust. B. triadicus is a common marine trace fossil mainly known from shallow-marine carbonate successions throughout the Phanerozoic. It is accompanied by other marine ichnotaxa such as Arachnostega gastrochaenae Bertling, Gastrochaenolites isp. aff. G. ornatus Kelly and Bromley, Spongeliomorpha iberica Saporta and Thalassinoides suevicus (Rieth). This ichnological evidence confirms the occurrence of short-term marginal-marine incursions in a predominantly lacustrine to palustrine environment.     

Genesis of the Nanyangtian scheelite deposit in southeastern Yunnan Province,China: evidence from mineral chemistry,fluid inclusions,and C–O isotopes

The Nanyangtian skarn-type scheelite deposit is an important part of the Laojunshan W–Sn polymetallic metallogenic region in southeastern Yunnan Province, China. The deposit comprises multiple scheelite ore bodies; multilayer skarn-type scheelite ore bodies are dominant, with a small amount of quartz vein-type ore bodies. Skarn minerals include diopside, hedenbergite, grossular, and epidote. Three mineralization stages exist: skarn, quartz–scheelite, and calcite. The homogenization temperatures of fluid inclusions in hydrothermal minerals that formed in different paragenetic phases were measured as follows: 221–423 °C (early skarn stage), 177–260 °C (quartz–scheelite stage), and 173–227 °C (late calcite stage). The measured salinity of fluid inclusions ranged from 0.18% to 16.34% NaCleqv (skarn stage), 0.35%–7.17% NaCleqv (quartz–scheelite stage), and 0.35%–2.24% NaCleqv (late calcite vein stage). Laser Raman spectroscopic studies on fluid inclusions in the three stages showed H₂O as the main component, with N₂ present in minor amounts. Minor amounts of CH₄ were found in the quartz–scheelite stage. It was observed that the homogenization temperature gradually reduced from the early to the late mineralization stages; moreover, δ¹³C_PDB values for ore-bearing skarn in the mineralization period ranged from ? 5.7‰ to ? 6.9‰ and the corresponding δ¹⁸O_SMOW values ranged from 5.8‰ to 9.1‰, implying that the ore-forming fluid was mainly sourced from magmatic water with a minor amount of meteoric water. Collectively, the evidence indicates that the formation of the Nanyangtian deposit is related to Laojunshan granitic magmatism.     

Early Cretaceous K-rich rhyolites from the Duolong Cu–Au deposit,southern Qiangtang,China: evidence for crustal growth

We report new zircon U–Pb age, Hf isotopic, and major and trace element data for rhyolites from the Duolong Ore Concentration Area of the Southern Qiangtang Terrane. Building on previous studies, we constrain the tectonic setting and propose a model to explain the geodynamics and crustal growth during regional magmatism in the Early Cretaceous. The analysed rhyolites yield laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb ages of 115 and 118 Ma. The rocks are K-rich (K₂O = 6.66–9.93 wt.%; K₂O/Na₂O = 8.2–19.7 wt.%), alkaline and peraluminous (A/CNK = 1.02–1.46), and are characterized by high SiO₂ contents (72.8–78.8 wt.%) similar to highly fractionated I-type granites. Fractionation of Fe–Ti oxides, plagioclase, hornblende, Ti-bearing phases, apatite, monazite, allanite and zircon contributed to the variations in major and trace element chemistry. High K₂O contents are likely due to partial melting of the continental crust. The samples have positive zircon εHf(t) values ranging from +7.1 to +11.2. These features, together with young zircon Hf crustal model ages of 489–721 Ma, indicate that the K-rich rhyolites were derived from juvenile lower crust with an input of a mantle-derived component. We suggest that the Early Cretaceous K-rich rhyolites formed in a continental arc setting during northward subduction of Bangong Co–Nujiang oceanic lithosphere. Basaltic magma underplating was responsible for vertical crustal growth, triggered by slab roll-back in the Duolong Ore Concentration Area in the Early Cretaceous.     

Magnetostratieraphy of the Red Beds in the Hengyang Basin

This paper discusses the Cretaceous-Tertiary magnetic polarity sequence of the the Hengyang Basin on the basis of magnetostratigraphic study. The age of each stratigraphic unit has been determined with the magnetic polarity time scale combined with 39Ar/40Ar dating, thus providing evidence for determining the geological ages of different formations. The authors assign the age of the Dongjing Formation of the Hengyang Basin to Early Cretaceous, the Shenhuangshan Formation to Early-Late Cretaceous, the Daijiaping Formation to Late Cretaceous, and the Dongtang and Xialiushi formations to Palaeocene.     

Sedimentology of a sandur formed by multiple jökulhlaups,Kverkfjöll,Iceland

The Kverkfjöll sandur in north Iceland is the furthest upstream of a suite of fluvial landforms extending for 200 km along the Jökulsá á Fjöllum river. Incision of the sandur exposes over 3 km of sedimentary sections, up to 15 m in height. A sandur wide, well-bedded succession of matrix-rich cobble-gravel and pebble/granule gravel, with individual beds 0.2 to 0.5 m thick indicates that the sandur is primarily the product of sandur-wide sheet-floods, with sediment-rich hyperconcentrated flows and also some debris flows and channelised turbulent flows. This interpretation is evidenced by bedded hyperconcentrated flow deposits occurring as laterally extensive tabular depositional units that dominate the entire sandur, reflecting the unconfined nature of the flow. Clast-supported boulder-gravel units interpreted as the product of macroturbulent flow occur in relatively narrow, but deep channels. The sedimentary succession is interpreted as the product of at least six volcanically generated catastrophic outburst floods (jökulhlaups) during the Little Ice Age. The sedimentology of these Little Ice Age flood deposits, on a small, high-gradient sandur, contrasts strongly with the deposits of volcanically-generated jökulhlaups on large, low-gradient coastal sandar, and sandar associated with retreating glaciers which have been the basis for most previous models of jökulhlaup sedimentation.     

Specific composition of native silver from the Rogovik Au–Ag deposit,Northeastern Russia

The first data on native silver from the Rogovik Au–Ag deposit in northeastern Russia are presented. The deposit is situated in central part of the Okhotsk–Chukchi Volcanic Belt (OCVB) in the territory of the Omsukchan Trough, unique in its silver resources. Native silver in the studied ore makes up finely dispersed inclusions no larger than 50 μm in size, which are hosted in quartz; fills microfractures and interstices in association with küstelite, electrum, acanthite, silver sulfosalts and selenides, argyrodite, and pyrite. It has been shown that the chemical composition of native silver, along with its typomorphic features, is a stable indication of the various stages of deposit formation and types of mineralization: gold–silver (Au–Ag), silver–base metal (Ag–Pb), and gold–silver–base metal (Au–Ag–Pb). The specificity of native silver is expressed in the amount of trace elements and their concentrations. In Au–Ag ore, the following trace elements have been established in native silver (wt %): up to 2.72 S, up to 1.86 Au, up to 1.70 Hg, up to 1.75 Sb, and up to 1.01 Se. Native silver in Ag–Pb ore is characterized by the absence of Au, high Hg concentrations (up to 12.62 wt %), and an increase in Sb, Se, and S contents; the appearance of Te, Cu, Zn, and Fe is notable. All previously established trace elements—Hg, Au, Sb, Se, Te, Cu, Zn, Fe, and S—are contained in native silver of Au–Ag–Pb ore. In addition, Pb appears, and silver and gold amalgams are widespread, as well as up to 24.61 wt % Hg and 11.02 wt % Au. Comparison of trace element concentrations in native silver at the Rogovik deposit with the literature data, based on their solubility in solid silver, shows that the content of chalcogenides (S, Se, Te) exceeds saturated concentrations. Possible mechanisms by which elevated concentrations of these elements are achieved in native silver are discussed. It is suggested that the appearance of silver amalgams, which is unusual for Au–Ag mineralization not only in the Omsukchan Trough, but also in OCVB as a whole, is caused by superposition of the younger Dogda–Erikit Hg-bearing belt on the older Ag-bearing Omsukchan Trough. In practice, the results can be used to determine the general line of prospecting and geological exploration at objects of this type.     

Platinum-group minerals from the Jinbaoshan Pd–Pt deposit,SW China: evidence for magmatic origin and hydrothermal alteration

The Jinbaoshan Pt–Pd deposit in Yunnan, SW China, is hosted in a wehrlite body, which is a member of the Permian (∼260 Ma) Emeishan Large Igneous Province (ELIP). The deposit is reported to contain one million tonnes of Pt–Pd ore grading 0.21% Ni and 0.16% Cu with 3.0 g/t (Pd + Pt). Platinum-group minerals (PGM) mostly are ∼10 μm in diameter, and are commonly Te-, Sn- and As-bearing, including moncheite (PtTe₂), atokite (Pd₃Sn), kotulskite (PdTe), sperrylite (PtAs₂), irarsite (IrAsS), cooperite (PtS), sudburyite (PdSb), and Pt–Fe alloy. Primary rock-forming minerals are olivine and clinopyroxene, with clinopyroxene forming anhedral poikilitic crystals surrounding olivine. Primary chromite occurs either as euhedral grains enclosed within olivine or as an interstitial phase to the olivine. However, the intrusion has undergone extensive hydrothermal alteration. Most olivine grains have been altered to serpentine, and interstitial clinopyroxene is often altered to actinolite/tremolite and locally biotite. Interstitial chromite grains are either partially or totally replaced by secondary magnetite. Base-metal sulfides (BMS), such as pentlandite and chalcopyrite, are usually interstitial to the altered olivine. PGM are located with the BMS and are therefore also interstitial to the serpentinized olivine grains, occurring within altered interstitial clinopyroxene and chromite, or along the edges of these minerals, which predominantly altered to actinolite/tremolite, serpentine and magnetite. Hydrothermal fluids were responsible for the release of the platinum-group elements (PGE) from the BMS to precipitate the PGM at low temperature during pervasive alteration. A sequence of alteration of the PGM has been recognized. Initially moncheite and atokite have been corroded and recrystallized during the formation of actinolite/tremolite, and then, cooperite and moncheite were altered to Pt–Fe alloy where they are in contact with serpentine. Sudburyite occurs in veins indicating late Pd mobility. However, textural evidence shows that the PGM are still in close proximity to the BMS. They occur in PGE-rich layers located at specific igneous horizons in the intrusion, suggesting that PGE were originally magmatic concentrations that, within a PGE-rich horizon, crystallized with BMS late in the olivine/clinopyroxene crystallization sequence and have not been significantly transported during serpentinization and alteration.     

Au-Pb compounds in nature: A general overview and new evidence from the Inagli Pt–Au placer deposit,the Aldan Shield,Russia

This study presents a new and first finding of Au-Pb intermetallic compounds in the Inagli Pt–Au placer deposit, the Republic of Sakha (Yakutia), Russia. This is the first time that all three accepted minerals (hunchunite, anyuiite and novodneprite), as well as unnamed Au-Pb intermetallics, corresponding in composition to Au_1.5Pb and AuPb, are present together in the same locality. We provide chemical compositions of Au-Pb compounds and host gold particles, describe morphology and relationships between different mineral phases. We also present an unexpected finding of unusual inclusion of Pb-Fe-aluminosilicate associated with K-feldspar and anyuiite in the gold grain. The new data together with data from other occurrences of Au-Pb compounds worldwide were reviewed to discuss type localities, mineralogy, conditions and possible mechanisms of formation of Au-Pb intermetallics and to provide an overview of current knowledge about these uniquely rare but naturally occurring minerals.     

Sm–Nd dating of fluorite from the worldclass Montroc fluorite deposit, southern Massif Central, France

A three-point Sm–Nd isotope isochron on fluorite from the very large Montroc fluorite vein deposit (southern Massif Central, France) defines an age of 111±13 Ma. Initial _Nd of –8.6 and initial ⁸⁷Sr/⁸⁶Sr of ~0.71245 suggest an upper crustal source of the hydrothermal system, in agreement with earlier work on fluid inclusions which indicated a basinal brine origin. The mid-Cretaceous age of ~111 Ma suggests the Albian/Aptian transition as the most likely period for large-scale fluid circulation during a regional extensional tectonic event, related to the opening of the North Atlantic ocean.Editorial handling: B. Lehmann     

Evolution of continental crust of the Aravalli craton,NW India,during the Neoarchaean–Palaeoproterozoic: evidence from geochemistry of granitoids

Neoarchaean–Palaeoproterozoic granitoids of the Aravalli craton, represented by four plutons with different ages, viz. Gingla (2.6–2.4 Ga), Ahar River (2562 Ma), Untala (2505 Ma), and Berach (2440 Ma) granitoids, are classified into three suites: TTG-like, Sanukitoid, and High-K Granitoid suite, all exhibiting negative Nb and Ti anomalies. The TTG-like suite is characterized by high contents of SiO₂, Na₂O, and LREEs, high (La/Yb)_N, low contents of K₂O, MgO, Cr, and Ni, and low (Dy/Yb)_N, suggesting that this suite formed by partial melting of a subducted basaltic slab without interacting with a mantle wedge. In contrast, the calc-alkaline Sanukitoid suite is marked by a high content of LILEs and mantle-compatible elements, which indicate that this suite formed by partial melting of a slab-fluid metasomatized mantle wedge in a subduction-related arc environment. On the other hand, the High-K Granitoid suite is characterized by high contents of SiO₂ and K₂O, and low contents of Na₂O, MgO, Cr, and Ni with variable Eu anomaly, along with high (La/Sm)_N and (La/Yb)_N, and low (Dy/Yb)_N and Nb/Th. Some high-K granitoids also exhibit A-type characteristics. These features indicate that the High-K Granitoid suite formed by melting of crustal rocks. Early Neoarchaean continental crust formation reflected a slab-melting-dominated magmatic process as evidenced by the TTG-like suite, whereas Palaeoproterozoic petrogenesis was governed by the interaction of slab melt with mantle wedge as demonstrated by the Sanukitoid suite. The High-K Granitoid suite formed during the waning stages of subduction. This study reveals that granitic rocks of the Aravalli craton evolved from slab melting in the Neoarchaean to melting of mantle wedge in the Palaeoproterozoic. Melting of older crust led to the formation of the High-K Granitoid suite.     

Metallogeny of the Longtangou-Huoyangou Sn deposit in North Qinling Orogeny: Geochronological and petrogeochemical evidence from Sn-bearing granite-pegmatiteSCIEI北大核心CSCD

北秦岭卢氏官坡地区龙潭沟-火炎沟锡矿床是近年来在豫西地区实现的重大找矿突破,然而前人对该矿床的形成时代以及成矿作用研究较少。本文以与锡成矿关系密切的白云母电气石钠长石花岗伟晶岩(以下称含锡花岗伟晶岩)为研究对象,开展了岩相学,岩石地球化学,以及锡石、铌钽铁矿和磷灰石LA-ICP-MS U-Pb年代学研究,探讨了花岗伟晶岩的源区性质、成岩成矿时代和构造环境。结果显示:(1)含锡花岗伟晶岩的锡石、铌钽铁矿和磷灰石U-Pb年龄分别为408.1±1.5Ma、391.5±2.0Ma和387.0±2.1Ma;锡石年龄代表早期锡矿化的时间,铌钽铁矿和磷灰石代表晚期铌钽矿化的时间;结合区域研究成果,认为官坡-丹凤地区存在两期锡铌钽等稀有金属成矿作用。(2)含锡花岗伟晶岩富硅和铝,贫碱,富集Rb、Cs、Nb、Ta和Hf,亏损Ba、P和Ti,相对富集重稀土元素,亏损轻稀土元素,具明显的Eu负异常,暗示其源岩应为陆壳物质。(3)龙潭沟-火炎沟锡矿床形成于造山后由挤压到伸展转换的构造背景。通过与秦岭造山带的灰池子复式岩体,以及成铀伟晶岩和稀有金属伟晶岩进行对比,我们认为,龙潭沟-火炎沟锡矿床的成锡伟晶岩地球化学特征既有相似性又有差异性,具更高的结晶分异演化程度;沉积源岩物质组成可能是龙潭沟-火炎沟伟晶岩成锡矿的关键。卢氏官坡地区龙潭沟-火炎沟锡矿床的发现,对于在昆仑-秦岭-大别地区找早泥盆世的稀有金属矿床,尤其是锡矿床,具有重要意义。     

Analytical Model for the Palaeoenvironmental Evolution of the Nihewan Beds

In this paper, the evolutional characteristics of palaeoclimate and oxidation-reduction conditions as well asacidity-alkalinity environment are discussed by means of the step-regression, cluster, optimal partitioning andcorrelation analyses of CaCO_3, C / P_2O_5, Fe~(2+) / Fe~(3+), pH and Eh values, taking the Xiaodukou section in theNihewan basin as an example. The CaCO_3, C / P_2O_5 and pH were calculated respectively using the optimalpartitioning method. Thus five cold zones and six warm zones as well as five reduction and six oxidation zoneswere distinguished. Then the inductive method was used to produce four numerical groups: 8.10, 8.3-8.4,8.6-8.7 and 8.9-8,97. The above-mentioned results are respectively based on CaCO_3 content, C/P_2O_5 andpH values. From Fig. 3, Tables 1 and 2 it can be seen that the Nihewan Beds were formed mainly under a re-duction and slightly alkaline environment of cold climate, with pH values of 8.3-8.4. Fig. 3 shows that bed 35is approximately near the boundary between the Brunhes and Matuyama polarity epochs, 0.73 Ma in age; bed26 is roughly near the Jaramillo event (base), 0.97 Ma in age; bed 18 coincides roughly with themagnetostratigraphic boundary of 2.00 Ma (?). Bed 13 may be the Pleistocene-Pliocene boundary, 2.48 Ma inage. Thus geochemical zones Ⅰ, Ⅱ, Ⅲ and Ⅳ include respectively cold zones 1; 2 and 3; 4; and 5.     

Minerals of the beudantite–segnitite series from the oxidation zone of the Berezovskoe gold deposit,middle Urals: Chemical variations,behavior of admixtures,and antimonian varieties

In the oxidation zone of the Berezovskoe gold deposit in the middle Urals, Russia, minerals of the beudantite–segnitite series (idealized formulas PbFe₃ ³⁺ AsO₄)(SO₄)(OH)₆ and PbFe₃ ³⁺ AsO₄)(AsO₃OH)(OH)₆, respectively) form a multicomponent solid solution system with wide variations in the As, S, Fe, Cu, and Sb contents and less variable P, Cr, Zn, Pb, and contents K. The found minerals of this system correspond to series from beudantite with 1.25 S apfu to S-free segnitite, with segnitite lacking between 1.57 and 1.79 As apfu. Segnitite at the Berezovskoe deposit contains presumably pentavalent Sb (up to 15.2 wt % Sb₂O₅ = 0.76 Sb apfu, the highest Sb content in the alunite supergroup minerals), which replaces Fe³⁺. The Sb content increases with increasing As/S value. On the contrary, beudantite is free of or very poor in Sb (0.00–0.03 Sb apfu). Many samples of segnitite are enriched in Cu (up to 8.2 wt% CuO = 0.83 Cu apfu, uncommonly high Cu content for this mineral) and/or in Zn (up to 2.0 wt% ZnO = 0.19 Zn apfu). Both Cu and Zn replace Fe. The generalized formula of a hypothetic end member of the segnitite series with 1 Sb apfu is Pb(Fe³⁺ M ²⁺Sb⁵⁺)(AsO₄)₂(OH)₆, where M = Cu, Zn, Fe²⁺. The chemical evolution of beudantite–segnitite series minerals at the Berezovskoe deposit is characterized by an increase in the S/As value with a decrease in the Sb content from early to late generations.     

Zoning in columbite-tantalite crystals from the granitic pegmatites of the Eräjärvi area,southern Finland

Electron microprobe analyses of zoned columbite-tantalite crystals from the granitic pegmatites of the Eräjärvi area in Orivesi, southern Finland indicate wide compositional variation within the series FeNb₂O₆-FeTa₂O₆-MnNb₂O₆-MnTa₂O₆, especially in specimens from thin pegmatite dikes.Most crystals show gentle progressive zoning characterized by small-scale variations in the major elements. Where the compositional variation is large, backscattered electron images indicate oscillatory or patchy zoning or various replacement textures.The zones in oscillatory zoned crystals are usually 1–50 μm in width, exceptions reaching 50–120 μm. The wider zones often consist of a group of very narrow subzones of only slightly different composition. Zoning is due mainly to the compositional variation in Ta and Nb. In two of these crystals, the oscillations in Mn follow the strongest oscillations in Nb content.Patchy zoned crystals exhibit corroded cores of early columbite-tantalite, surrounded by later zones enriched in Ta. The mottled appearance of such crystals results from two or more successive replacements. Replacement tongues or network-like replacement textures are typical in the rims of some crystals.The zoning of the columbite-tantalite is related to the complex crystallization history of the pegmatite dikes. The main factors controlling oscillatory zoning are considered to be the growth dynamics of the crystals, the concentration and diffusion of the main elements, and the successive flows of the magma in an intrusion channel. The generation of a corrosive supercritical vapor phase at the end of magmatic crystallization caused resorption, patchy zoning and the replacement of the columbite-tantalite.     

Defrocking the false father of the ‘Driftless Area’, USA

The Driftless Area is a designation popular in American promotional tourist literature for an area in four contiguous American states, Minnesota, Wisconsin, Iowa and Illinois, that were not glaciated during the latest ice advance. Geographer Lawrence Martin published several articles asserting that geologist William H. Keating first discovered this area in 1823, an error that has crept into subsequent accounts. But historical evidence goes to show that three geologists, Roland D. Irving, Newton H. Winchell and Thomas C. Chamberlin, were simultaneous originators of the concept as we understand it today, about the year 1877.     

Geochemical evidence for a multi-source origin of manganese in the Montaña de Manganeso deposit,central Mexico

The Montaña de Manganeso is a manganese vein-type deposit spatially associated with back-arc basin remnants of the Guerrero tectonostratigraphic terrane. The study of major- and trace-element geochemical characteristics of the deposit provides insight into the controls on ore-forming processes within the area. The deposit is characterized by low Co, Cu and Ni abundances, and high Ba (>10,000 ppm) contents and Mn/Fe ratios (<500), typical of hydrothermal Mn deposits. In addition, the low ∑REE abundances (18.7 to 103 ppm), negative Ce anomalies (0.2 to 0.6), and positive Y (1.00 to 2.34) and Eu anomalies (0.6 to 4.4) also suggest a hydrothermal source for the deposit. Discrimination plots involving ∑REE and Zr vs. (Cu + Ni + Co) and Ce/Ce* vs. Nd and Y/Ho further indicate a hydrothermal source in an oxidizing depositional environment. The Mn-Fe-(Ni + Cu + Co), MnO₂-MgO-Fe₂O₃, (Cu/Zn)/Fe₂O₃ vs. (Zn/Ni)/MnO₂ and Na/Mg diagrams display intermediate signatures between marine and terrestrial environments. This suggest that the Montaña de Manganeso deposit is the result of two metallogenic stages: (I) the earliest stage, which involved the formation of Mn oxides by hydrothermal/diagenetic processes in the Arperos back-arc basin during the Cretaceous; and (II) the latest stage took place subsequent to accretion the Guerrero tectonostratigraphic terrane onto the continent and involved the remobilization of the Cretaceous submarine Mn oxides (and associated trace elements) and subsequent redepositation by Tertiary continental hydrothermal activity.