Platiniferous gold–tourmaline aggregates in the gold–palladium belt of Minas Gerais,Brazil: implications for regional boron metasomatism

Mineralogy and Petrology - The platiniferous gold–palladium belt of Minas Gerais, Brazil, forms an approximately 240-km-long, roughly north–south-trending domain that includes numerous...     

Assessment of gold mineralisation in Osu–Amuta–Itagunmodi areas,Southwestern Nigeria

Tight conglomerate reservoirs have complex pore structure and strong heterogeneity which could bring great difficulties in the identification of oil and wa     

As–Sb–Bi–Au mineralization in the Baogutu gold deposit,Xinjiang, NW China

Here we report the occurrence of some uncommon mineral assemblages including pääkönenite, aurostibite, native arsenic, native antimony, and native bismuth found in the Baogutu gold deposit in the western Junggar, Xinjiang, NW China. The mineralization could be generally subdivided into two types: the gold-bearing quartz-vein type mineralization and disseminated mineralization in the wall rocks. The sulfide minerals in gold lodes commonly include pyrite, arsenopyrite, marcasite, and stibnite. However, the L7 lode in No. 4 orebody and the L1 lode in No. 11 orebody of the Baogutu gold deposit are quite different in terms of their mineral assemblages. The L7 lode contains native arsenic–quartz veins in shallow levels and stibnite–quartz veins at depth. Gold-bearing minerals (electrum, native gold, and rarely aurostibite) mainly coexist with pääkönenite, stibnite, native arsenic, and native antimony. The crystallization of As- and Sb-bearing minerals was likely to have consumed H₂S from the hydrothermal fluid, which probably triggered the precipitation of native gold. The L1 lode consists of several discontinuous sulfide-dominated lensoid orebodies. The massive sulfide ores that produced most of the gold resource are characterized by an intimate association between native bismuth and native gold mineralization.     

Lode–gold mineralization in the Tanami region, northern Australia

The Tanami region of northern Australia has emerged over the last two decades as the largest gold-producing region in the Northern Territory. Gold is hosted by epigenetic quartz veins in sedimentary and mafic rocks, and by sulfide-rich replacement zones within iron formation. Although limited, geochronological data suggest that most mineralization occurred at about 1,805–1,790 Ma, during a period of extensive granite intrusion, although structural relationships suggest that some deposits predate this period. There are three main goldfields in the Tanami region: the Dead Bullock Soak goldfield, which hosts the world-class Callie deposit; The Granites goldfield; and the Tanami goldfield. In the Dead Bullock Soak goldfield, deposits are hosted by carbonaceous siltstone and iron formation where a late (D₅) structural corridor intersects an early F₁ anticlinorium. In The Granites goldfield, deposits are hosted by highly sheared iron formation and are interpreted to predate D₅. The Tanami goldfield consists of a large number of small, mostly basalt-hosted deposits that probably formed at a high structural level during D₅. The D₅ structures that host most deposits formed in a convergent structural regime with σ ₁ oriented between E–W and ENE–WSW. Structures active during D₅ include NE-trending oblique thrust (dextral) faults and ESE-trending (sinistral) faults that curve into N- to NNW-trending reverse faults localized in supracrustal belts between and around granite complexes. Granite intrusions also locally perturbed the stress field, possibly localizing structures and deposits. Forward modeling and preliminary interpretations of reflection seismic data indicate that all faults extend into the mid-crust. In areas characterized by the N- to NW-trending faults, orebodies also tend to be N- to NW-trending, localized in dilational jogs or in fractured, competent rock units. In areas characterized by ESE-trending faults, the orebodies and veins tend to strike broadly east at an angle consistent with tensional fractures opened during E–W- to ENE–WSW-directed transpression. Many of these deposits are hosted by reactive rock units such as carbonaceous siltstone and iron formation. Ore deposition occurred at depths ranging from 1.5 to 11 km from generally low to moderate salinity carbonic fluids with temperatures from 200 to 430°C, similar to lode–gold fluids elsewhere in the world. These fluids are interpreted as the product of metamorphic dewatering caused by enhanced heat flow, although it is also possible that the fluids were derived from coeval granites. Lead isotope data suggest that lead in the ore fluids had multiple sources. Hydrogen and oxygen isotope data are consistent with both metamorphic and magmatic origins for ore fluids. Gold deposition is interpreted to be caused by fluid unmixing and sulfidation of host rocks. Fluid unmixing is caused by three different processes: (1) CO₂ unmixing caused by interaction of ore fluids with carbonaceous siltstone; (2) depressurization caused by pressure cycling in shear zones; and (3) boiling as ore fluids move to shallow levels. Deposits in the Tanami region may illustrate the continuum model of lode–gold deposition suggested by Groves (Mineralium Deposita 28:366–374, 1993) for Archean districts.     

Kysylga gold–silver deposit in the terrigenous sequences of the Verkhoyansk–Kolyma mesozoides

The paper reports the mineralogical and geochemical features of the Kysylga gold deposit located in the hornfelsed Norian sedimentary rocks and classified with low-sulfide gold–quartz type of deposits typical of the Verkhoyansk–Kolyma metallogenic province. Detailed typomorphic study of the major minerals (quartz, arsenopyrite, and gold) of the ore veins shows that the deposit is assigned to the gold–silver type. Mineralogical and geochemical data substantiate this conclusion.     

Platinum–palladium–gold mineralization in the Nkenja mafic–ultramafic body, Ubendian metamorphic belt, Tanzania

Significant and widespread enrichment of platinum, palladium, and gold has been found within the Nkenja mafic–ultramafic body located in southern Tanzania in the central part of the Ubendian metamorphic belt. This body is dominated by partly serpentinized chromitiferous dunite, wehrlite and olivine clinopyroxenite, which are tectonically intercalated with amphibolitized metagabbro. The dunites contain both disseminated and seam-type chrome spinel with an Al-rich composition. The seams are thin, impersistent and, together with enclosing dunite, often show deformation at granulite facies conditions. Forsterite contents of olivine in the dunite range from 87 to 92?mol%. Clinopyroxene in wehrlite and clinopyroxenite is diopsidic with significant contents of Al and Na. Clinopyroxene forms irregular bands and crosscutting veins in the dunite, as well as occurring as weakly dispersed isolated grains in the dunite. Elevated levels of Pt, Pd and Au occur in all ultramafic rocks, but not amphibolitized metagabbro, and there is a weak correlation between high abundances of platinum-group element (PGE) and chromitites. PGE values are erratically distributed and are associated with trace to minor amounts of disseminated sulphides (pyrrhotite, pentlandite, heazlewoodite, chalcopyrite and bornite). The abundances of all PGE are consistently anomalous, suggesting a primary igneous control by sulphides in ultramafic rock. However, there has evidently been a strong metamorphic and/or hydrothermal overprint on what was probably an original magmatic concentration of PGE-bearing sulphides. Geological mapping and petrological evidence, as well as the style of PGE sulphide mineralization, are consistent with the Nkenja ultramafic body being part of the crustal section of a dismembered Palaeoproterozoic ophiolite.     

Processes of high-T fluid–rock interaction during gold mineralization in carbonate-bearing metasediments: the Navachab gold deposit,Namibia

The Navachab gold deposit in the Damara belt of central Namibia is hosted by a near-vertical sequence of amphibolite facies shelf-type metasediments, including marble, calc-silicate rock, and biotite schist. Petrologic and geochemical data were collected in the ore, alteration halos, and the wall rock to evaluate transport of elements and interaction between the wall rock and the mineralizing fluid. The semi-massive sulfide lenses and quartz–sulfide veins are characterized by a complex polymetallic ore assemblage, comprising pyrrhotite, chalcopyrite, sphalerite, and arsenopyrite, native bismuth, gold, bismuthinite, and bismuth tellurides. Mass balance calculations indicate the addition of up to several orders of magnitude of Au, Bi, As, Ag, and Cu. The mineralized zones also record up to eightfold higher Mn and Fe concentrations. The semi-massive sulfide lenses are situated in the banded calc-silicate rock. Petrologic and textural data indicate that they represent hydraulic breccias that contain up to 50 vol.% ore minerals, and that are dominated by a high-temperature (T) alteration assemblage of garnet–clinopyroxene–K-feldspar–quartz. The quartz–sulfide veins crosscut all lithological units. Their thickness and mineralogy is strongly controlled by the composition and rheological behavior of the wall rocks. In the biotite schist and calc-silicate rock, they are up to several decimeters thick and quartz-rich, whereas in the marble, the same veins are only a few millimeters thick and dominated by sulfides. The associated alteration halos comprise (1) an actinolite–quartz alteration in the biotite schist, (2) a garnet–clinopyroxene–K-feldspar–quartz alteration in the marble and calc-silicate rock, and (3) a garnet–biotite alteration that is recorded in all rock types except the marble. The hydrothermal overprint was associated with large-scale carbonate dissolution and a dramatic increase in CO₂ in the ore fluid. Decarbonation of wall rocks, as well as a low REE content of the ore fluid resulted in the mobilization of the REE, and the decoupling of the LREE from the HREE. The alteration halos not only parallel the mineralized zones, but may also follow up single layers away from the mineralization. Alteration is far more pronounced facing upward, indicating that the rocks were steep when veining occurred. The petrologic and geochemical data indicate that the actinolite–quartz– and garnet–clinopyroxene–K-feldspar–quartz alterations formed in equilibrium with a fluid (super-) saturated in Si, and were mainly controlled by the composition of the wall rocks. In contrast, the garnet–biotite alteration formed by interaction with a fluid undersaturated in Si, and was mainly controlled by the fluid composition. This points to major differences in fluid–rock ratios and changes in fluid composition during alteration. The alteration systematics and geometry of the hydrothermal vein system are consistent with cyclic fluctuations in fluid pressure during fault valve action. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Utilization of SPOT 5 data for mapping gold mineralized diorite–tonalite intrusion,Bulghah gold mine area,Saudi Arabia

The present study utilizes the processed SPOT 5 data to discriminate and to generate 1:10,000 geologic image map to delineate the mineralized diorite–tonalite intrusion around Bulghah gold mine area, Saudi Arabia. The rock units exposed in the area include gossan, marble, Hulayfah volcanics, diorite–tonalite, gneissose granite, and alkali granite. Gold mineralization at Bulghah mine is hosted mainly by Syn- to Late-tectonic diorite–tonalite intrusion aligned along N–S direction and is associated mainly with cataclastic zones and quartz veins. Gossans and jasparoidal gossans (Hulayfah group), recorded at the western side of Bulghah mine area as discontinuous small lenses, can be easily discriminated on 4/2 and 4/3 band ratio SPOT images by their white and black image signatures, respectively. Granitoids (gneissose granite and alkali granite) are easily discriminated in 3/2 ratio image, in which gneissose granite has gray image signature, whereas alkali granite has dark gray image signature. On the SPOT false color composite band ratios image (3/2 R, 4/2 G, and 4/3 B), gossan, marble, Hulayfah volcanics, diorite–tonalite, gneissose granite, and alkali granite have sky blue, blood red, bluish light brown, orange, brick red, and deep blue colors, respectively. Fusion of the false color composite SPOT ratios image (3/2 R, 4/2 G, and 4/3 B) with the high spatial resolution SPOT pan image is performed using IHS transformation method. The fused image is used to delineate the mineralized diorite–tonalite intrusion and to produce 1:10,000 geologic image map for Bulghah gold mine area. The present study reveals the usefulness of the processed SPOT 5 data for adding new extensions at the southern and northern boundaries of diorite–tonalite intrusion.     

Disseminated gold–sulfide mineralization at the Zhaima deposit,eastern Kazakhstan

The Zhaima gold–sulfide deposit is located in the northwestern part of the West Kalba gold belt in eastern Kazakhstan. The mineralization is hosted in Lower Carboniferous volcanic and carbonate rocks formed under conditions of marginal-sea and island-arc volcanic activity. The paper considers the mineralogy and geochemistry of primary gold–sulfide ore and Au-bearing weathering crusts. Au-bearing arsenopyrite–pyrite mineralization formed during only one productive stage. Disseminated, stringer–disseminated, and massive rocks are enriched in Ti, Cr, V, Cu, and Ni, which correspond to the mafic profile of basement. The main ores minerals are represented by finely acicular arsenopyrite containing Au (up to few tens of ppm) and cubic and pentagonal dodecahedral pyrite with sporadic submicroscopic inclusions of native gold. The sulfur isotopic composition of sulfides is close to that of the meteoritic standard (δ³⁴S =–0.2 to +0.2). The ⁴⁰Ar/³⁹Ar age of three sericite samples from ore veinlets corresponds to the Early Permian: 279 ± 3.3, 275.6 ± 2.9, and 272.2 ± 2.9 Ma. The mantle source of sulfur, ore geochemistry, and spatial compatibility of mineralization with basic dikes allow us to speak about the existence of deep fluid–magmatic systems apparently conjugate with the Tarim plume.     

The Variscan Tamlalt–Menhouhou gold deposit,Eastern High-Atlas,Morocco

The Tamlalt–Menhouhou gold deposit belongs to the Neoproterozoic–Palaeozoic Tamlalt inlier located in the Eastern High-Atlas (Morocco). It occurs in altered Upper Neoproterozoic bimodal volcanic and volcano-sedimentary units outcropping in the Tamlalt–Menhouhou area. Gold mineralization has been identified in quartz veins related to shear-zones associated with a strong quartz-phyllic-argillic alteration. Visible free gold is related to goethite–malachite–barite boxworks in quartz veins. The other alteration minerals accompanying gold mineralization are mainly carbonates, chlorite, hematite, albite and pyrite whose relative proportion defines three alteration types. ⁴⁰Ar/³⁹Ar geochronology performed on phengite grains from phyllic alteration and the auriferous quartz veins, yields plateau ages ranging from 300 ± 5 Ma to 284 ± 12 Ma with a weighted mean age of 293 ± 7 Ma. This identifies a Late Variscan age for the Tamlalt–Menhouhou “shear zones-related” gold deposit and emphasizes the consequences of the Variscan orogeny for gold mineralization in the High-Atlas and Anti-Atlas Neoproterozoic inliers.     

Prospectivity for epithermal gold–silver deposits in the Deseado Massif,Argentina

Previous prospectivity modelling for epithermal Au–Ag deposits in the Deseado Massif, southern Argentina, provided regional-scale prospectivity maps that were of limited help in guiding exploration activities within districts or smaller areas, because of their low level of detail. Because several districts in the Deseado Massif still need to be explored, prospectivity maps produced with higher detail would be more helpful for exploration in this region.We mapped prospectivity for low- and intermediate-sulfidation epithermal deposits (LISEDs) in the Deseado Massif at both regional and district scales, producing two different prospectivity models, one at regional scale and the other at district-scale. The models were obtained from two datasets of geological evidence layers by the weights-of-evidence (WofE) method. We used more deposits than in previous studies, and we applied the leave-one-out cross validation (LOOCV) method, which allowed using all deposits for training and validating the models. To ensure statistical robustness, the regional and district-scale models were selected amongst six combinations of geological evidence layers based on results from conditional independence tests.The regional-scale model (1000 m spatial resolution), was generated with readily available data, including a lithological layer with limited detail and accuracy, a clay alteration layer derived from a Landsat 5/7 band ratio, and a map of proximity to regional-scale structures. The district-scale model (100 m spatial resolution) was generated from evidence layers that were more detailed, accurate and diverse than the regional-scale layers. They were also more cumbersome to process and combine to cover large areas. The evidence layers included clay alteration and silica abundance derived from ASTER data, and a map of lineament densities. The use of these evidence layers was restricted to areas of favourable lithologies, which were derived from a geological map of higher detail and accuracy than the one used for the regional-scale prospectivity mapping.The two prospectivity models were compared and their suitability for prediction of the prospectivity in the district-scale area was determined. During the modelling process, the spatial association of the different types of evidence and the mineral deposits were calculated. Based on these results the relative importance of the different evidence layers could be determined. It could be inferred which type of geological evidence could potentially improve the modelling results by additional investigation and better representation.We conclude that prospectivity mapping for LISEDs at regional and district-scales were successfully carried out by using WofE and LOOCV methods. Our regional-scale prospectivity model was better than previous prospectivity models of the Deseado Massif. Our district-scale prospectivity model showed to be more effective, reliable and useful than the regional-scale model for mapping at district level. This resulted from the use of higher resolution evidential layers, higher detail and accuracy of the geological maps, and the application of ASTER data instead of Landsat ETM + data. District-scale prospectivity mapping could be further improved by: a) a more accurate determination of the age of mineralization relative to that of lithological units in the districts; b) more accurate and detailed mapping of the favourable units than what is currently available; c) a better understanding of the relationships between LISEDs and the geological evidence used in this research, in particular the relationship with hydrothermal clay alteration, and the method of detection of the clay minerals; and d) inclusion of other data layers, such as geochemistry and geophysics, that have not been used in this study.     

Environmental assessment of copper–gold–mercury mining in the Andacollo and Punitaqui districts,northern Chile

The Coquimbo region has been one of the richest producers of Cu, Au and Hg in Chile, and some of the deposits have been mined almost continuously since the 16th century. To assess the potential environmental contamination in this region, the authors measured the concentration of Cu, As, Cd, Zn and Hg in samples of stream and mine waters, stream sediments, soils, flotation tailings, and mine wastes in the Andacollo (Cu, Au, Hg) and Punitaqui (Cu–Au, Hg) districts. The concentration of Hg in the atmosphere in these districts were also measured. Although contamination is strongly controlled by the ore in each district, metal dispersion is modified by the degree of metallurgical processing efficiency as shown by the outdated Cu flotation system at Andacollo (stream sediments Cu 75–2200 μg/g). Conversely, more efficient procedures at Punitaqui resulted in less stream contamination, where stream sediments contained Cu ranging from 110–260 μg/g. However, efficient concentration by flotation of a given metal (e.g. Cu) may lead to the loss of another (e.g. Hg up to 190 μg/g in the tailings at Punitaqui), and therefore, to contamination via erosion of the tailings (downstream sediments Hg concentrations up to 5.3 μg/g). Continued use of Hg for Au amalgamation at Andacollo has led to significant contamination in stream sediments (0.2–3.8 μg/g Hg) and soils (2.4–47 μg/g Hg). Communities in this region are underdeveloped, and decades of inefficient treatment of flotation tailings and waste-rock stock piles has resulted in significant contamination of the surrounding landscape.     

Native gold in complex Ti–Zr placers of the southern West Siberian Plain

Typomorphic features of native gold and its contents in complex Ti–Zr placers in the southern West Siberian Plain are reported. Three of the placers are of littoral-marine genesis, and two formed under conditions of an alluvial piedmont plain. Native gold from the studied Ti–Zr placers occurs mainly as flattened thin (?0.1 mm) particles which underwent mechanical action. It is marked by wide fineness variation and the abundance of a very fine (990–1000‰) variety. Most likely, this is chemically transformed clastogenic metal. The gold content of the productive bed (5–30 mg/m³ native gold and 8–140 ppb bulk gold) is consistent with the dispersion of heavy ore and accessory minerals during mechanical migration in water flows simultaneously with their concentration on geochemical barriers. The native-gold content of complex Ti–Zr placers shows a higher negative correlation with the primary source–placer distance than those of Ti and Zr minerals and a positive correlation with the degree of hydrodynamic reworking (gravity concentration) of transit terrigenous material. On the southern framing of the West Siberian Plain, some regions of northern Kazakhstan are promising for gold of complex Ti–Zr placers as well as fine- and thin-gold placers, gold-bearing weathering crusts, and primary gold deposits.     

Listvenite–lode association at the Barramiya gold mine,Eastern Desert,Egypt

Several occurrences of gold-bearing quartz veins are situated along the east–northeast-trending Barramiya–Um Salatit ophiolitic belt in the central Eastern Desert of Egypt. In the Barramiya mine, gold mineralization within carbonaceous, listvenized serpentinite and adjacent to post-tectonic granite stocks points toward a significant role of listvenitization in the ore genesis. The mineralization is related to quartz and quartz–carbonate lodes in silicified/carbonatized wallrocks. Ore minerals, disseminated in the quartz veins and adjacent wallrocks are mainly arsenopyrite, pyrite and trace amounts of chalcopyrite, sphalerite, tetrahedrite, pyrrhotite, galena, gersdorffite and gold. Partial to complete replacement of arsenopyrite by pyrite and/or marcasite is common. Other secondary phases include covellite and goethite. Native gold and gold–silver alloy occur as tiny grains along micro-fractures in the quartz veins. However, the bulk mineralization can be attributed to auriferous arsenopyrite and arsenic-bearing pyrite (with hundreds of ppms of refractory Au), as evident by electron microprobe and LA-ICP-MS analyses.The mineralized quartz veins are characterized by abundant carbonic (CO₂ ± CH₄ ± H₂O) and aqueous-carbonic (H₂O–NaCl–CO₂ ± CH₄) inclusions along intragranular trails, whereas aqueous inclusions (H₂O–NaCl ± CO₂) are common in secondary sites. Based on the fluid inclusions data combined with thermometry of the auriferous arsenopyrite, the pressure–temperature conditions of the Barramiya gold mineralization range from 1.3 to 2.4 kbar at 325–370 °C, consistent with mesothermal conditions. Based on the measured δ³⁴S values of pyrite and arsenopyrite intimately associated with gold, the calculated δ³⁴S_Σs values suggest that circulating magmatic, dilute aqueous-carbonic fluids leached gold and isotopically light sulfur from the ophiolitic sequence. As the ore fluids infiltrated into the sheared listvenite rocks, a sharp decrease in the fluid fO₂ via interaction with the carbonaceous wallrocks triggered gold deposition in structurally favorable sites.     

Tokur gold ore–placer cluster in Amur Province: Geological–structural features and perspective of its development

The geological–structural features and gold-potential perspective of the Tokur ore–placer cluster in the Amur Province have been studied. This ore–placer cluster is a syncline composed of Paleozoic blackshale sequence, which is cut through by Late Paleozoic and Late Mesozoic intrusions. A granitoid massif is suggested at the depth on the basis of geophysical data. The cluster is distinguished by high productivity. Approximately 37 t gold from ore deposits, primarily from the Tokur deposit, and 60 t from placers have been mined out. The Tokur deposit is compared with the Natalka and Degdekan deposits from the Yana–Kolyma Province. Perspectives of the cluster area for large gold–quartz deposits and technogenic gold placers have been estimated.     

Alteration and mineral zonation at the Mt Lyell copper–gold deposit,Tasmania

The Mount Lyell copper deposits are located in the middle Cambrian Mount Read volcanic belt of western Tasmania and consist of more than 24 separate copper–gold–silver orebodies. The dominant copper mineralisation style is disseminated pyrite–chalcopyrite subvertical pipes with subordinate chalcopyrite–bornite ± other copper phases, massive pyrite and base metal sulfides. A zonation in mineralisation style within the pipes is defined from chalcopyrite–magnetite at depth to chalcopyrite–pyrite at intermediate levels, to chalcopyrite–bornite at the shallowest level. Alteration is developed broadly symmetrically around the ore zones and zoned from quartz–chlorite–phengite ± biotite at depth to quartz–muscovite at intermediate levels, and a quartz–muscovite–pyrophyllite–zunyite assemblage at the shallowest levels. This is interpreted to be a result of a fluid that evolved from hot, reduced and neutral conditions at depth to cool, oxidised and acidic conditions at the shallowest level. The chalcopyrite–bornite deposits occur at the top of the hydrothermal system and are associated with intensely silicified rock and muscovite/pyrophyllite alteration. The close relationship of these deposits with the top of the pipes suggests they are part of a single mineralising event. Where the chalcopyrite–bornite deposits are juxtaposed with the Owen Group, rather than a simple chalcopyrite–bornite mineralogy, there are numerous other copper phases, which represent higher oxidation states and collectively suggest variable and fluctuating fluid conditions during deposition. It is proposed that these deposits are formed by an interaction of the reduced hydrothermal fluid with an oxidised fluid generated at very shallow levels within and during deposition of the Owen Group. Mineralisation within the middle Owen Group sandstones and clasts of altered rock within the middle and upper Owen Group sediments marks the end of the hydrothermal system. Around the entire edge of the Mt Lyell field, there is a variation in the white mica composition from proximal muscovite to distal phengite that represents the neutralisation of the hydrothermal fluid by fluid–wall rock interaction.     

Fe–Cu deposits in the Kangdian region,SW China: a Proterozoic IOCG (iron-oxide–copper–gold) metallogenic province

Numerous Fe–Cu deposits are hosted in the late Paleoproterozoic Dongchuan and Dahongshan Groups in the Kangdian region, SW China. The Dongchuan Group is composed of siltstone, slate, and dolostone with minor volcanic rocks, whereas the Dahongshan Group has undergone lower amphibolite facies metamorphism and consists of quartz mica-schist, albitite, quartzite, marble and amphibolite with local migmatite. Deposits in the Dongchuan Group are commonly localized in the cores of anticlines, in fault bends and intersections, and at lithological contacts. Orebodies are closely associated with breccias, which are locally derived from the host rocks. Fe-oxides (magnetite and/or hematite) and Cu-sulfides (chalcopyrite, bornite) form disseminated, vein-like and massive ores, and typically fill open spaces in the host rocks. The deposits have extensive albite alteration and local K-feldspar alteration overprinted by quartz, carbonate, sericite and chlorite. Deposits in the Dahongshan Group have orebodies sub-parellel to stratification and show crude stratal partitioning of metals. Fe-oxide ores occur as massive and/or banded replacements within the breccia pipes, whereas Cu-sulfide ores occur predominantly as disseminations and veinlets within mica schists and massive magnetite ores. Ore textures suggest that Cu-sulfides formed somewhat later than Fe-oxides, but are possibly within the same mineralization event. Both ore minerals predated regional Neoproterozoic metamorphism. Both orebodies and host rocks have undergone extensive alteration of albite, scapolite, amphibole, biotite, sericite and chlorite. Silica and carbonate alterations are also widespread. Ore-hosting strata have a LA-ICP-MS zircon U–Pb age of 1681 ± 13 Ma, and a dolerite dyke cutting the Fe-oxide orebodies has an age of 1659 ± 16 Ma. Thus, the mineralization age of the Dahongshan deposit is constrained at between the two. All ores from the two groups have high Fe and low Ti, with variable Cu contents. Locally they are rich in Mo, Co, V, and REE, but all are poor in Pb and Zn. Sulfides from the Fe–Cu deposits have δ³⁴S values mostly in the range of +2 to +6 per mil, suggesting a mix of several sources due to large-scale leaching of the strata with the involvement of evaporites. Isotopic dating and field relationships suggest that these deposits formed in the late Paleoproterozoic. Ore textures, mineralogy and alteration characteristics are typical of IOCG-type deposits and thus define a major IOCG metallogenic province with significant implications for future exploration.