Remobilization Of Sulfides Research Articles

Ore Remobilization History of the Metamorphosed Rävliden North Volcanogenic Massive Sulfide Deposit, Skellefte District, Sweden

Abstract The Skellefte district in northern Sweden hosts many volcanogenic massive sulfide (VMS) deposits and is considered one of the most important European mining districts for Cu, Zn, Pb, Ag, and Au. The volcanic and sedimentary rocks that the VMS deposits are hosted in were deformed during the Svecokarelian orogeny, with three documented regional deformation phases. These events imparted a distinct attitude and geometry to the deposits, their host succession, and discordant zones of synvolcanic hydrothermal alteration. Few studies have investigated the detailed deformation effects on the sulfide minerals. In this contribution, we document the structural characteristics and remobilization history of mineralization at the Rävliden North Zn-Pb-Cu-Ag deposit—one of the most important recent discoveries in the district consisting of 8.5 million tonnes (Mt) grading 1.01% Cu, 3.45% Zn, 0.53% Pb, 78.60 g/t Ag, and 0.23 g/t Au. At Rävliden, massive to semimassive sphalerite-rich mineralization with lesser pyrrhotite, galena, pyrite, and silver minerals occurs structurally above stringer-type mineralization dominated by chalcopyrite, pyrrhotite, and pyrite. These mineralization types exhibit evidence of deformation and remobilization such as (1) sulfide-alignment parallel to tectonic foliations; (2) rounded wall-rock tectonoclasts in a ductile deformed sulfide matrix (“ball ore” or durchbewegt ore); and (3) sulfides in tension gashes, strain shadows, piercement veins, and late, straight veinlets crosscutting tectonic fabrics. These features are attributed to polyphase deformation during the D1, D2, and D3 events at temperature ranging from 200° to 550°C. Remobilization of sulfides was mostly within the bounds of the main mineralization (i.e., 10–100 m), with few local external occurrences. A combination of solid-state and fluid-assisted remobilization processes are inferred. Rare brittle veinlets and zeolite-cemented breccias with sphalerite, galena, and silver minerals occur in the stratigraphic hanging wall, where they crosscut all Svecokarelian structures. This mineralization type is highly reminiscent of Phanerozoic low-T vein- and breccia-hosted Pb-Zn deposits of the Lycksele-Storuman area west of Rävliden North, which have been linked to far-field effects associated with the opening of the Iapetus Ocean (0.7–0.5 Ga). We suggest that this Zn-Pb mineralizing event led to the formation of the late sulfide-zeolite veinlets and breccias at Rävliden North, and that elements such as Ag and Sb within this mineralization were locally remobilized from Rävliden.

Sulfide Remobilization in the Metamorphosed Kayad Sedimentary Exhalative Zn-Pb Deposit, Western India: Evidence from Mode of Occurrence, Texture, Hydrothermal Alteration Features, and Trace Element Chemistry

Abstract The Kayad Zn-Pb deposit, situated within the Proterozoic Aravalli-Delhi fold belt in western India, is primarily characterized by sphalerite and galena along with pyrrhotite and chalcopyrite. The mineralization occurs as disseminated ores in quartzite, disseminated/laminated and massive ores in quartz-mica schist, and in pegmatite and quartz veins. The laminated ores conform to the regional schistosity and folding, whereas the massive Zn-Pb ores postdate the pervasive tectonic fabric, accumulating at the fold hinges. The massive ore is characterized by durchbewegung texture, discrete blebs of galena and chalcopyrite in a sphalerite matrix with low interfacial angles, and discrete intergrowths of sulfides and sulfosalts such as pyrargyrite, gudmundite, Ag-tetrahedrite, and breithauptite. Geochemical analyses of sulfides reveal microinclusions of sulfosalts comprising Ag, Sb, Cu, Tl, and As, which are regarded as low-melting chalcophile elements (LMCEs). Hydrothermal alteration is insignificant in the laminated and massive ores but prominent around Fe-Cu ± Zn-Pb and Zn-Pb ± Fe-Cu veins. The alteration assemblages in these veins evince a pervasive K + Na ± Fe alteration, later overprinted by a subsidiary Ca ± Na alteration. We interpret the laminated/disseminated ores to be of syndiagenetic sedimentary-exhalative (SedEx) origin formed within an euxinic basin. Conversely, the textural features, mineralogical composition, lack of associated hydrothermal alterations, and evident structural influence on the emplacement of the massive ores suggest they have been remobilized both via plastic flow and by sulfide partial melting. Temperature estimates of up to 650°C, derived from Ti-in-biotite geothermometry of the metamorphosed host rocks, indicate lower-middle amphibolite facies conditions during regional metamorphism. The initiation of melting at these temperatures was promoted by the desulfurization of pyrite to pyrrhotite in quartz-mica schist, aided by melting point depression due to the presence of LMCEs like Ag, Sb, and As.

Nature and origin of primary ore-forming fluids in the highly metamorphosed Archean Hongtoushan VMS deposit, North China: Insights from in situ S isotopes and trace elements of sulfides

Many ancient volcanogenic massive sulfides (VMS) deposits underwent various degrees of deformation and metamorphism, which modified the primary orebody geometries and sulfide textures, resulting in the great challenge of revealing the source and physicochemical properties of primary ore-forming fluids and original mineralization processes. Here, we observed the textural evolution of sulfides in the highly metamorphosed Archean VMS Hongtoushan Cu-Zn deposit, China, to constrain the histories and P-T conditions of metamorphic remobilization and to evaluate the influence of metamorphism on geochemical characteristics of sulfide. Further, the in situ sulfur isotopic and trace elemental analyses were utilized to reveal the source and physicochemical conditions of initial fluids. During metamorphism, pyrite developed elongated texture, bulging recrystallization, coarse porphyroblasts, and foam texture. These textures all occurred at a temperature of 550 – 700 °C, at which sulfide remobilization and deformation occurred in an anhydrous environment. The geochemical exchange among sulfides did not happen during metamorphism. The sulfur isotope and trace elements of sulfides thus can be used to track the source and physicochemical properties of primary ore-forming fluids. In situ sulfur isotopic analyses of sulfides yielded values of δ34S approaching zero and Δ33S situating mass-dependent isotope fractionation (MDF) area, indicating that the sulfur of the original submarine hydrothermal system was mainly derived from the magmatic fluids. The content of Se in pyrite revealed the primary fluids were acidic and reductive and were used to constrain the temperature of ore-forming fluids, which was higher than 250 °C. The ratio of Co/Ni of pyrite was higher than 10, indicating primary fluids were of magmatic-hydrothermal origin. The high content of Se and As in pyrite and Cd and Hg in sphalerite documented that these elements were partially derived from the magmatic volatiles or magma degassing process. Overall, our study demonstrates that coupling textures and in situ geochemical features of sulfides could be a helpful tool for tracking the primary ore-forming processes of the metamorphosed massive sulfide deposits.

Impact of deformation and metamorphism on sphalerite chemistry – Element mapping of sphalerite in carbonate-hosted Zn-Pb sulfide deposits of the Kootenay Arc, southern British Columbia, Canada and northeastern Washington, USA

Sphalerites from the Kootenay Arc in British Columbia and Washington State were selected to represent three types of carbonate-hosted massive sulfide deposits, including Mississippi Valley-type (MVT), Irish-type, and fracture-controlled replacement type (FCR). These deposits were variably deformed and metamorphosed during the Cordilleran orogen. Laser ablation inductively coupled plasma mass spectrometric (LA-ICP-MS) analyses of the trace element distributions within the sphalerites are combined with petrography and sulfur isotope analyses to evaluate the influence of primary trace element signatures, along with the variable influence of post-ore metamorphism and deformation on sulfide remobilization and trace element redistribution.Mississippi Valley-type (Josephine orebodies) and Irish-type (Yellowhead orebodies) at Pend Oreille mine are only weakly deformed and recrystallized, so their sulfide minerals commonly retain primary ore textures. The sphalerite from the Irish-type deposit has positive narrow range of δ34S values (17.9–20.5‰, mean 19.2‰), and it is enriched in Ge, Tl and Pb, but depleted in Cd, Mn, and Cu relative to MVT and FCR deposits. Germanium is concentrated in dark-brown acicular-colloform bands where micro-inclusions of a germanium oxide mineral (argutite (GeO2)) and galena have been detected. Other MVT deposits of the Kootenay Arc (Reeves MacDonald, Jersey-Emerald, HB, Jackpot-Lerwick, Duncan) are more deformed and metamorphosed than the Irish-type deposit of the Pend Oreille mine and primary ore textures are only locally preserved. There is a progressive increase in deformation and degree of recrystallization from Reeves MacDonald, located away from intrusions, to deposits within the contact metamorphic aureoles of intrusions (HB, Jersey-Emerald, Jackpot-Lerwick). Sphalerite from the least metamorphosed Reeves MacDonald deposit has high Cd, Ga, Pb, and Tl contents, high Cd/Ge and Ga/In values, and the lowest δ34S values (7.4 to 11.1‰, mean 8.8‰). In contrast, sphalerites from contact metamorphosed HB, Jersey-Emerald and Jackpot-Lerwick deposits have higher δ34S values (13.3 to 28.5‰, mean 19.2‰), are enriched in Mn and Fe, with higher Zn/Cd and Mn/Fe values relative to Reeves MacDonald deposit. These enrichments and fractionations correspond to the breakdown of pyrite and pyrrhotite and the thermal annealing of sphalerite caused by contact metamorphism. Sulfide minerals from the FCR deposit (Abbott-Wagner) are undeformed (except for microfractures) and only weakly recrystallized. Sphalerite from the FCR Abbott-Wagner deposit is enriched in Cu, Ga, In, and Sn as primary source signatures relative to sphalerite from MVT and Irish-type deposits. This reflects the more complex mineral assemblage of galena, sphalerite, pyrite, chalcopyrite, and tetrahedrite in this deposit. The presence of chalcopyrite and tetrahedrite is consistent with a higher-temperature origin of the FCR deposit relative to the lower-temperature MVT and Irish-type deposits.This study demonstrates that the high spatial resolution of in-situ LA-ICP-MS analyses of trace element within sphalerites, in combination with petrography and other analytical techniques (e.g., electron microprobe, secondary ion mass spectrometry, field emission scanning electron microscopy) characterizes the behavior and distribution of trace elements in sphalerite for three deposit types and variable conditions of regional and contact metamorphism. Understanding the effects of metamorphism and deformation on trace elements can be very useful in exploration for deposits rich in critical metals.

Sulfide remobilization and trace element redistribution during metamorphism and deformation at the Xitieshan Pb-Zn deposit, NW China

The effects of post-ore metamorphism and deformation on trace element concentrations in sulfides have recently received increasing attention. In this study, we report comprehensive petrographic observations combined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace element analysis data of pyrite, sphalerite, and chalcopyrite to evaluate the influence of regional metamorphism and deformation on sulfide remobilization and trace element distribution in the metamorphosed volcanic-sediment-hosted Xitieshan deposit, NW China. The Xitieshan deposit, located in the central segment of the North Qaidam orogenic belt along the northeastern margin of the Tibetan Plateau, is one of the largest Pb-Zn producers in China. Marble-hosted mineralization accounts for approximately 80% of the total mineral resources with the rest hosted in schist in this deposit. Petrographic studies coupled with detailed field work revealed that sulfide minerals in marble-hosted mineralization generally preserve the primary ore textures well with respect to the original mineralization. In contrast, sulfide minerals in schist-hosted ores exhibit various brittle and ductile deformation textures, including cataclasis, recrystallization, annealing, Durchbewegung, fracture healing textures, and veinlets, indicating that sulfide remobilization during metamorphism and deformation was most likely achieved by the combination of mechanical and chemical processes.LA-ICP-MS trace element data for pyrite grains with inclusion-rich cores (Py1b) inside “clean” inclusion-free overgrowth (Py3) indicate that the recrystallization of pyrite both expels trapped inclusions and liberates trace elements such as Cr, Mn, Ni, Cu, Zn, Ag, In, Sn, and Sb. Py3 contains more As than Py1, suggesting that the enrichment of As into recrystallized pyrite occurred during metamorphism. Compared to primary sphalerite (Sp1), the deformed counterpart (Sp2) is characterized by the depletion of In, which could be attributed to (a) remobilization of In into recrystallized chalcopyrite, and/or (b) remobilization and diffusion of In out of primary sphalerite and subsequent formation of the indium-bearing mineral during metamorphism. Indium, Sn, and Ag concentrations were significantly higher in recrystallized chalcopyrite grains than in other analyzed sulfide minerals, indicating that these elements are preferentially incorporated into chalcopyrite under metamorphic conditions.Trace element signatures for deformed and recrystallized pyrite, sphalerite, and chalcopyrite resemble previously reported data from other massive sulfide deposits that have undergone metamorphism and deformation elsewhere. Original mineralization at Xitieshan formed in a high-temperature, magmatically-driven hydrothermal system, which is indicated by the high Co/Ni ratios in pyrite, elevated concentrations of Sn in chalcopyrite and indium in sphalerite, and high calculated temperatures (350–420 ℃) by using the novel “Ga-Ge-In-Mn-Fe in sphalerite” geothermometer.

Carmacks Copper Cu-Au-Ag Deposit: Mineralization and Postore Migmatization of a Stikine Arc Porphyry Copper System in Yukon, Canada

Abstract Late Triassic to Early Jurassic porphyry Cu mineralization is common in British Columbia, yet there are few age-equivalent porphyry occurrences in Yukon. This study presents new data for the enigmatic Carmacks Copper Cu-Au-Ag deposit in south-central Yukon, Canada, which is hosted in amphibolite facies metamorphic inliers within the Early Jurassic Granite Mountain batholith. Sulfide mineralization occurs mainly as net-textured bornite and chalcopyrite in leucosome, and as chalcopyrite ± pyrite blebs and disseminations in amphibolite and quartz-plagioclase-biotite schist. Several studies suggest that the Carmacks Copper deposit and the nearby Minto deposit are related to porphyry belts in British Columbia, but constraining the timing of alteration, mineralization, and metamorphism has been difficult. This study establishes a geologic and high-precision geochronologic framework for sulfide mineralization and its host rocks at the Carmacks Copper deposit, using Re-Os dating of molybdenite, and chemical abrasion-thermal ionization mass spectrometry (CA-TIMS) analysis of both whole zircon grains and laser-cut fragments of complexly zoned zircon grains. Our data indicate that the igneous protolith of the metamorphic inliers formed at 217.53 ± 0.16 Ma, followed by peak metamorphism at amphibolite facies at 205.82 ± 0.23 Ma, which occurred prior to Granite Mountain batholith emplacement but subsequent to Cu-Au-Ag mineralization of the protolith. An early phase of the Granite Mountain batholith was emplaced at 199.84 ± 0.14 Ma, followed by the main phase at 195 to 194 Ma. A second generation of metamorphic zircon in migmatite at 196.01 ± 0.12 Ma represents a partial melting event associated with Granite Mountain batholith emplacement. Two petrographically distinct populations of molybdenite are present in unstrained, net-textured copper sulfides. A sample dominated by strained molybdenite yielded an 187Re/187Os age of 212.5 ± 1.0 Ma, which represents the minimum mineralization age of the protolith. A sample dominated by euhedral grains yielded an 187Re/187Os age of 198.5 ± 0.9 Ma, constraining the maximum age of sulfide remobilization. These results indicate that primary mineralization is >212.5 Ma and potentially coeval with the ~217.5 Ma generation of Late Triassic magmatism. The mineralized protolith, best interpreted as the potassic alteration zone of a Late Triassic (~217–213 Ma) porphyry Cu-Au system, was metamorphosed to amphibolite facies at ~206 Ma, and subsequently migmatized during 200 to 194 Ma intrusion of the Granite Mountain batholith. The chalcopyrite-bornite-dominant assemblage in neosome precipitated from an immiscible Cu-Fe-S melt phase that partly consumed xenocrystic molybdenite and reprecipitated new molybdenite grains. The Carmacks Copper deposit and the related Minto deposit are remnants of a Late Triassic porphyry belt, where a significant fraction of the original metal endowment was likely lost through digestion of mineralized rocks by midcrustal magma in the Early Jurassic. These Yukon deposits are rare examples of metamorphosed porphyry Cu systems in the global geologic record, where rapid tectonic burial following mineralization was the principal factor in their preservation.

Copper Sulfide Remobilization and Mineralization during Paleoproterozoic Retrograde Metamorphism in the Tongkuangyu Copper Deposit, North China Craton

The Tongkuangyu copper deposit, North China Craton, is hosted in a volcano-sedimentary sequence (ca. 2.2 Ga) that metamorphosed to the lower amphibolite facies at ca. 1.9 Ga. Petrographic observations revealed various metamorphic fabrics (mineral alignment and foliations) and several generations of biotite, chlorite, and pyrite. Sulfide Pb-Pb dating indicates that copper mineralization occurred at 1960+46/−58 Ma, younger than the zircon U-Pb age of the host metatuff (2180 Ma to 2190 Ma), but close to the timing of regional metamorphism (ca. 1.9 Ga). Electron probe analyses show that the biotites belong to the magnesium-rich variety, and were formed at 470 to 500 ° C based on Ti-in-biotite thermometry. Chlorites belong to ripidolite and pycnochlorite, and were formed at ca. 350 ° C based on the Al geothermometer. Pyrites in porphyry, metatuffs, and quartz veins have contrasting Ni and Co concentrations, pointing to a local remobilization. Hydrogen and oxygen isotopic analyses suggest that biotite and chlorite were formed by metamorphic waters whereas quartz records much lower δ D f l u i d values, reflecting the influence of meteoric water. Fluid inclusions in pyrite and chalcopyrite in metatuff and quartz vein contain extremely radiogenic 4 He and 40 Ar, indicating a crustal origin for the fluids. Sulfides show a magmatic sulfur isotopic signature, likely indicating the presence of preexisting volcanism-related sulfides. We proposed that the early layered copper sulfides formed during metamorphic retrogression at ca. 1.9 Ga and the late vein-type sulfides were derived from the remobilization of the earlier sulfides by infiltration of external fluids such as residual seawater and metamorphic fluids at shallow level.

Geology and metamorphism of the neoproterozoic Mangabal Complex: An example of Ni[sbnd]Cu-PGE mineralized intrusion in the Goiás Magmatic Arc, central Brazil

Inserted in the context of the Goiás Magmatic Arc, the Mangabal Complex represents a partially metamorphosed mafic-ultramafic intrusion, which is part of a cluster of neoproterozoic layered bodies formed during the Brasiliano Orogeny in central Brazil. The Mangabal Complex is composed of two exposures, the northern and the southern members, which exhibit the similar igneous mineralogy, crystallization sequence and were affected by the same metamorphic conditions. The stratigraphy of the Mangabal Complex can be divided into three main zones: i. the Lower Mafic Zone (LMZ), composed of adcumulatic norite and, forming the basal portion of the southern member; it is composed of adcumulatic norite; ii. the Ultramafic Zone (UZ), characterized by dunite and harzburgite cumulates, and iii. the Upper Mafic Zone (UMZ), consisting predominantly of norite, with restricted interlayeres of feldspathic dunite-orthocumulate. Petrographic data reveal a crystallization sequence for the Mangabal Complex formed by Olivine + Cr-Spinel > Olivine + Orthopyroxene > Orthopyroxene + Plagioclase > Clinopyroxene. In the olivine cumulus, the forsterita (Fo) content (Fo 78–85) suggest a moderately primitive parental magma. The NiCu-PGE mineralization occurs as disseminated sulfides, located in the UMZ, UZ and LMZ cumulate rocks, or forming massive to net-textured bodies in the metamorphic rocks of the UMZ. The main sulphide assemblage is composed of pyrrhotite + pentlandite + chalcopyrite ± pyrite, with minor pyrite + millerite. Disseminated sulphides are present in igneous rocks as well as in the metamorphic rocks that still partially preserve their original primary texture. This fact, together with the occurrence of abundant olivine and chromium-bearing spinel cumulates, suggests a fertile magma for the Mangabal Complex. However, the highest S, Ni, Cu, and PGE contents correlate positively with and are related to amphibolite and calc-silicate rocks associated with shear zones, indicating that metamorphism and deformation processes were critical in promoting the remobilization of sulphides and their deposition along shear zones. The primary mineral assemblage was largely replaced due to high-pressure upper-amphibolite facies metamorphism. The paragenesis representing metamorphic peak conditions is composed of kyanite + orthoamphibole + hornblende, which reveals pressures of approximately 8.5 kbar and a temperature up to 750 °C. The metamorphic mineral assemblage, together with the proximity to the São Luis de Montes Belos shear zone, suggests that kyanite crystallization in the Mangabal Complex and similar layered intrusions worldwide might be linked to the development of major crustal-scale structures.

Syn-tectonic sulphide remobilization and trace element redistribution at the Falun pyritic Zn-Pb-Cu-(Au-Ag) sulphide deposit, Bergslagen, Sweden

Mineralization types at the Palaeoproterozoic Falun base metal sulphide deposit are predominantly pyritic Zn-Pb-Cu-rich massive sulphide mineralization, disseminated to semi-massive Cu-Au mineralization, auriferous quartz veins, and mineralized shear zones of talc-chlorite-dominated schist. The massive and disseminated to semi-massive sulphide mineralization types were subject to polyphase ductile deformation (D1 and D2) and metamorphism under low-P, lower-amphibolite facies conditions, which led to the development of ore textures and paragenetic relationships indicating both mechanical and chemical remobilization of sulphides. In the massive sulphide mineralization, rare inclusion-rich pyrite occurs as relic cores inside inclusion-poor metamorphosed pyrite. Imaging and spot analysis using multielement laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) reveal that inclusion-poor pyrite was depleted in trace elements, which were originally present as non-stoichiometric lattice substitutions or in mineral inclusions. The inclusion-rich pyrite was shielded from depletion and, at least partly, retained its initially higher trace element concentrations, including Au.Gold is also associated with chalcopyrite in the disseminated to semi-massive Cu-Au mineralization and in the system of auriferous quartz veins hosted therein, the latter being also affected by the D2 ductile strain. It is inferred that emplacement of the vein system took place after the peak of metamorphism, which occurred between D1 and D2, but prior to and possibly even shortly after completion of the D2 deformational event. Similarities in trace element signatures in chalcopyrite are compatible with the interpretation that the quartz veins formed by local chemical remobilization of components from the Cu-Au mineralization. Transport of liberated Au from pyrite during grain growth in the massive sulphide mineralization may have upgraded the Au endowment in the quartz veins, leading to the additional formation of native gold in the veins. A strong correspondence between elements liberated from pyrite (e.g. Pb, Bi, Se and Au) and those forming discrete and characteristic mineral phases in the quartz veins (Pb-Bi sulphosalts, native gold) supports this hypothesis.Trace element signatures for the main sulphide minerals pyrite, chalcopyrite, sphalerite and galena are similar to previously published data from other metamorphosed massive sulphide deposits. The association of the Falun mineralization with elevated Bi is reflected by its occurrence in sulphide minerals (e.g. galena) and in abundant mineral inclusions of Pb-Bi sulphosalts (e.g. weibullite), especially in the disseminated to semi-massive Cu-Au mineralization. Elevated Sn concentrations in the lattice and/or as cassiterite inclusions in chalcopyrite, sphalerite and galena are compatible with a hot, acidic and reducing fluid during formation of the syn-volcanic, base metal sulphide mineralization and associated host-rock alteration.

Structural controls on mineralisation at the Namib Lead and Zinc Mine, Damara Belt, Namibia

The Namib Lead and Zinc (Pb-Zn) Mine is hosted within the Karibib Formation of the Swakop Group, Damara Sequence. The host marble contains sulphide-rich beds and is locally Pb- and Zn-rich over a strike extent of >100 km. Mining took place in the upper portions of a remobilized MVT or SEDEX orebody, which may occur adjacent to a reactivated major structure. Pb and Zn show locally anomalous copper, tin, indium and fluorine concentrations. Based on the position of gossans, individual orebodies comprise discrete elongate shoots around an antiform and its meso-scale parasitic folds, within calcitic marble. Non-coaxial flattening of the fold-cleavage geometry reflects a series of non-coaxial deformation events, recorded in the Southern Central Zone of the Damara Belt which were superimposed on a NE-SW structural grain and pre-existing fold axial planes. Non-coaxial flattening resulted in further remobilization of sulphides into dilational rhombs which formed from shearing along overlapping axial planar cleavage, in concert with the dilation of banding in the host marble.

Tectonic and metallogenic evolution of the Curaçá Valley Copper Province, Bahia, Brazil: A review based on new SHRIMP zircon U-Pb dating and sulfur isotope geochemistry

More than three hundred mafic-ultramafic bodies of different sizes, containing copper sulfide mineralization, are present in the Curaçá River Valley Copper Province, northeastern São Francisco Craton, Bahia State, Brazil, covering an area of about 1700 km2. The basement, supracrustal sequence, and mafic-ultramafic intrusive rocks underwent granulite facies metamorphism and were reworked during the evolution of the Itabuna-Salvador-Curaçá Orogeny, resulting in retrograde metamorphism to the amphibolite facies, partial migmatization, and intrusion of granitic and syenitic rocks. During the slow and progressive rise of the terrain, hydrothermal reactions mainly along shear zones retrogressed part of these rocks to assemblages characteristic of the greenschist metamorphic facies. The main orebodies with copper sulfide minerals are associated with pyroxenite, mica-rich (glimmerite) and noritoid rocks. The present investigation focuses on the major Caraíba, Sussuarana, Surubim, and Vermelhos deposits. Chalcopyrite and bornite compose the ore, in a ratio of 70–30%, with copper grade varying between 0.69% and 1.4%, and associated gold and silver. The sulfide minerals are invariably accompanied by magnetite. Two mineralization styles are distinguished: (i) disseminated in non-altered mafic-ultramafic rocks; and (ii) tectonic controlled related to hydrothermal alteration zones. New geochronological data show that quartz-microcline metasomatites of the Caraíba Mine contain Neoarchean inherited zircons (upper intercept at 2723 ± 51 Ma), related to the early stages of magmatism, whereas Orosirian ages (2047 ± 12 and 2042 ± 15 Ma) are related to the main hydrothermal mineralization activity. Norite from the Surubim Mine has a Paleoproterozoic age (2047 ± 11 Ma), and the dated gabbro shows Pb loss in the Neoproterozoic, probably related to the Brasiliano Orogeny (670–490 Ma). Previous studies have demonstrated that the main hydrothermal event is Paleoproterozoic. Phlogopite Ar-Ar dating from the Caraíba Mine yields plateau-ages around 2000–2100 Ma. A cluster of δ34S values approaching zero is related to interstitial sulfide minerals in the least-altered ultramafic rocks, while values above and below zero are related to remobilized sulfides. These data support the hypothesis of the existence of a primary (magmatic) mineralizing event, alleged to have precipitated disseminated, interstitial sulfide minerals, and a second (hydrothermal) event, responsible for the economically more important mineralization, which is structurally controlled and related to significant potassic alteration. The sulfide minerals are associated with different generations of magmatic and hydrothermal magnetite, as well as distal plagioclase and microcline alteration halos. The combination of these features reaffirms the concept that the Curaçá Valley deposits may be part of the same alteration system, as described in IOCG deposits, with the deepest deposits being located further south. Based on the data obtained during the present study, it is possible to establish a tectono-metallogenic evolutionary model to explain the genesis of the copper mineralization in the Curaçá Valley. The mafic-ultramafic bodies were emplaced as multiple intrusions in Neoarchean arc-related gneisses and chemical sediments, along with bornite and chalcopyrite mineralization. The sulfide minerals that preserve the characteristics of this stage are chalcopyrite or bornite, both with δ34S values around 0‰V-CDT.A continental collision affected the Caraíba arc and the related sequences between 2100 and 2080 Ma. During this Rhyacian-Orosirian orogeny, deformation and amphibolite-granulite facies metamorphism, the rocks underwent partial melting, and sapphirine formation developed. Between 2050 and 2020 Ma, the main mineralization stage took place at Caraíba, Vermelhos, and Surubim, which corresponds to an earlier stage in the Sussuarana deposits. The southern deposits were formed deeper than those to the north, resulting in less extensive potassic alteration and related hydrothermal mineralization. The sulfide minerals of the deeper deposits have negative δ34S (between 0‰ and −6.81‰), to slightly positive values, where the igneous protoliths are best preserved. This alteration took place near the brittle-ductile boundary, mainly associated with ductile structures.The latest stage of mineralization took place between 1950 and 1920 Ma, in the Caraíba, Vermelhos and Surubim deposits, along with major sulfide remobilization in Sussuarana. This stage was characterized by the participation of oxidizing fluids, possibly meteoric waters, which raised the δ34S values up to +11.77‰.

The Occurrence of Breithauptite and Nisbite-Like Sb-Ni Phases At Sindesar-Khurd, Rajasthan, India: Implications For Melt-Assisted Sulfide Remobilization

Abstract Breithauptite (NiSb) generally occurs in magmatic Ni-Cu-PGE ores and in hydrothermal veins associated with Ni and Co arsenide minerals. Its presence in the Rajpura-Dariba–Sindesar-Khurd–Bethumni metallogenic belt, Rajasthan, India, may be ascribed to metamorphic remobilization as observed elsewhere, e.g ., Sulitjelma, Norway. From the coexistence of breithauptite with probable Sb-Ni melt phases at Sindesar-Khurd, a temperature of approximately 930–970 °C is indicated from the phase relations in the Ni-Sb binary phase diagram. However, this temperature is substantially above the peak metamorphic temperature of 580–600 °C estimated from equilibrium silicate phase assemblages in the rocks around the Rajpura-Dariba ore body, which is situated six kilometers to the south of Sindesar-Khurd. We have conducted experiments at 600 °C in the Ni–Sb system in the presence of Ag to understand if Ag is responsible for such a drastic decrease of the temperature of melting. The presence of other phases including freibergite [(Ag,Cu,Fe,Zn) 12 Sb 4 S 13 ], Ag-rich tetrahedrite [(Cu,Ag,Fe,Zn) 12 Sb 4 S 13 ], ∼2FeS.Ag 2 S, and ∼CuPbSbS 3 .Ag 2 S along with breithauptite at Sindesar-Khurd indicates the selective incorporation of Ag. In a second assemblage nisbite (NiSb 2 ) instead of breithauptite was observed along with 3PbS.Ag 2 S, 2Ag 2 S.FeS, (Fe,Ag)S, a Sb-Ni-Ag-Fe-S phase, and a Ag-Sb-Ni-Cu-Fe-S phase. Nisbite is stable only below 628 °C, suggesting that these assemblages formed below this temperature, and the presence of several additional phases of variable compositions further indicates disequilibrium and probable rapid crystallization from a melt. Our results suggest that Ag significantly depresses melting temperatures in the Ni–Sb system, making possible the existence of an Ag-Sb-Ni melt at 600 °C. In the presence of S and other elements such as Fe, Pb, Cu, etc . the melting temperature would be further depressed. Thus the removal of Ag from the melt through formation of Ag-bearing phases, e.g ., 2FeS.Ag 2 S, 3PbS.Ag 2 S, 2Ag 2 S.FeS, or CuPbSbS 3 .Ag 2 S, may result in a residual metastable melt at the ambient temperature. Such a melt may quench to a fine-grained assemblage containing breithauptite and nisbite-like Sb-Ni solid phases, such as encountered at Sindesar-Khurd. The second assemblage, which is nisbite-bearing, could result from a relatively Ag-rich Ni-poor melt fraction that becomes extremely Sb-rich due to the removal of Ag.

Spatial and temporal variability of surface water and groundwater before and after the remediation of a Portuguese uranium mine area

The old Senhora das Fontes uranium mine, in central Portugal, consists of quartz veins which penetrated along fracture shear zones at the contact between graphite schist and orthogneiss. The mine was exploited underground until a depth of 90m and was closed down in 1971. The ores from this mine and two others were treated in the mine area by the heap-leach process which ended in 1982. Seven dumps containing a total of about 33,800m3 of material and partially covered by natural vegetation were left in the mine area. A remediation process took place from May 2010 to January 2011. The material deposited in dumps was relocated and covered with erosion resisting covers. Surface water and groundwater were collected in the wet season just before the remediation, in the following season at the beginning of the remediation and also after the remediation in the following dry season. Before, at the beginning and after the remediation, surface water and groundwater have an acid-to-alkaline pH, which decreased with the remediation, whereas Eh increased. In general, before the remediation, uranium concentration was up to 83μg/L in surface water and up to 116μg/L in groundwater, whereas at the beginning of the remediation it increases up to 183μg/L and 272μg/L in the former and the latter, respectively, due to the remobilization of mine dumps and pyrite and chalcopyrite exposures, responsible for the pH decrease. In general, after the remediation, the U concentration decreased significantly in surface water and groundwater at the north part of the mine area, but increased in both, particularly in the latter up to 774μg/L in the south and southwest parts of this area, attributed to the remobilization of sulphides that caused mobilization of metals and arsenic which migrated to the groundwater flow. Uranium is adsorbed in clay minerals, but also in goethite as indicated by the geochemical modelling. After the remediation, the saturation indices of oxyhydroxides decrease as pH decreases. The remediation also caused decrease in Cd, Co, Cr, Ni, Pb, Zn, Cu, As, Sr and Mn concentrations of surface water and groundwater, particularly in the north part of the mine area, which is supported by the speciation modelling that shows the decrease of most dissolved bivalent species. However, in general, after the remediation, Th, Cd, Al, Li, Pb, Sr and As concentrations increased in groundwater and surface water at south and southwest of the mine area. Before and after the remediation, surface water and groundwater are contaminated in U, Cd, Cr, Al, Mn, Ni, Pb, Cu and As. Remediation caused only some improvement at north of the mine area, because at south and southwest part, after the remediation, the groundwater is more contaminated than before the remediation.

Rio Tinto (Iberian Pyrite Belt): a world-class mineral field reopens

The deposits of Rio Tinto are located in the Spanish segment of the Iberian Pyrite Belt and are hosted within felsic porphyritic volcanic rocks and tuffs. The orebodies comprise a spectrum from sedimentary exhalative (San Antonio) to sub-sea floor replacement of the volcanic host rocks (Filon Norte); the two largest masses (San Dionisio and Filon Sur) are closely associated with black shale and probably formed by partial replacement of these units in an anoxic setting. Alteration associated with ore deposition is typified by marginal sericitic (white mica) alteration, and central chloritisation and silicification in a multi-phase alteration history. Structures formed during initial plate convergence may have acted as controls on ore deposition, and evidence of such controls is retained in the distribution of various elements in the sulphide deposits. Tectonism followed the mineralisation, and overprinted previous extensional events and resulted in the development of slaty cleavage in the pelitic rocks with partial remobilisation of sulphides, and tight folds with associated shearing of the southern limb.

Strong remanent magnetization in pyrrhotite: A structurally controlled example from the Paleoproterozoic Tanami orogenic gold province, northern Australia

Rocks associated with an orogenic gold system in the Paleoproterozoic Granites/Tanami Inlier of northern Australia exhibit strong natural remanent magnetism, identifiable in regional aeromagnetic data. Petrographical analysis indicates the two dominant magnetic minerals in the rocks of this region are multidomain magnetite and monoclinic pyrrhotite. Chemical analysis using an electron microprobe has determined that the magnetite and pyrrhotite are stoichiometrically pure, without significant elemental substitution. Alternating field demagnetization, Curie Temperature, and hysteresis analysis indicates that the remanently magnetized phase is monoclinic pyrrhotite with low magnetic susceptibility. In contrast, multidomain magnetites lack remanence and have high magnetic susceptibilities. Pyrrhotite is preserved in the rock mass along with other sulfide minerals as millimeter-scale veins parallel to regionally developed, penetrative mylonitic shear bands (c-planes) formed during sulfide remobilization in the waning, cooling stages of hydrothermal Au deposition. In contrast, magnetite grains exhibit porphyroblastic textures, consistent with formation during prograde to peak metamorphism, indicating formation prior to pyrrhotite, earlier in the orogenic cycle. Because of the low Curie Temperature ( ca. 325 °C) of pyrrhotite, it is therefore likely that remanent magnetization effects observed in aeromagnetic images of the Tanami Inlier, are associated with structures intimately related to the late stages of Au mineralization during retrograde greenschist metamorphism after the peak thermal point of the orogenic cycle.

Structural Modification of the Komatiite-Associated Harmony Nickel Sulfide Deposit, Leinster, Western Australia

The Harmony nickel sulfide deposit (3.2 Mt of ore) is situated along the eastern margin of the Agnew-Wiluna greenstone belt, Eastern Goldfields, Western Australia. The deposit occurs 2 km north of the larger Rocky’s Reward (15.9 Mt) and Perseverance (50.7 Mt) deposits. The mine stratigraphy trends north-northwest–south-southeast, dips moderately (30°–80°) to the west, is overturned, and metamorphosed to middle-amphibolite facies grades (about 550°C, 3 kbars). Stratigraphic footwall units to the west of the nickel-bearing komatiite include ca. 2720 to 2725 Ma (volcano-) sedimentary rocks and rhyodacite volcanic and volcaniclastic units. Hanging-wall units comprise mainly reworked sedimentary or volcaniclastic rocks interlayered with at least two barren spinifex-textured komatiite units exposed in the mine area. Exhalative pyrite-rich pelitic units and thin amphibolite units are locally present in the footwall and hanging wall. The nickeliferous komatiite is thickest in the center of the deposit and thins to the north, south, and at depth. Although massive sulfides and minor disseminated sulfides are mainly located along the sheared western footwall contact, minor massive sulfides occur throughout the komatiite and country rock in fold hinges, boudin neck areas, brittle-ductile shear zones, piercement cusps, piercement veins, and brittle faults. Footwall and hanging-wall units have a strong composite fabric defined by compositional layering and several subparallel axial planar foliations. East-west shortening resulted in the folding of the composite fabric to form abundant north-northwest–trending, tight, asymmetric, moderately (20°–40°) N- and S-plunging folds. The asymmetric folds thicken the komatiite and orebodies in the center of the pit and control deposit-scale orebody plunge directions. The attenuated north-northwest–trending komatiite fold limbs are boudinaged and concentrate pods of massive sulfides in boudin neck positions. Relaxation in horizontal shortening coincided with open recumbent folding of the steeply dipping limbs of earlier upright asymmetric folds. A resumption of east-west shortening in a brittle stress regime resulted in the remobilization of massive sulfides into east-west–trending brittle faults. The concentration of massive sulfides in brittle-ductile to brittle structures indicates that massive sulfide remobilization spanned a diverse range of deformation and metamorphic conditions. The present geometry and distribution of stratigraphy and orebodies at Harmony reflect a complex interplay of primary magmatic and secondary overprinting processes. Remobilized massive sulfide orebodies are an important exploration target in other deformed and metamorphosed terranes that host primary Ni-Cu-(PGE) deposits. Although footwall units are the preferential host to remobilized massive sulfide shoots, massive sulfides are commonly remobilized within shear zones and faults zones and hosted by hanging-wall units up to 50 m from their primary footwall position. In cases of folding, orebodies tend to be elongate parallel to the plunge direction of fold axes or mineral stretching lineation, and potential exploration targets occur along the trend of known folded ore shoots and more specifically along the plunge line of such shoots.

The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden, part I: geology

The Kristineberg volcanic-hosted massive sulphide (VMS) deposit, located in the westernmost part of the Palaeoproterozoic Skellefte district, northern Sweden, has yielded 22.4 Mt of ore, grading 1.0% Cu, 3.64% Zn, 0.24% Pb, 1.24 g/t Au, 36 g/t Ag and 25.9% S, since the mine opened in 1941, and is the largest past and present VMS mine in the district. The deposit is hosted in a thick pile of felsic to intermediate and minor mafic metavolcanic rocks of the Skellefte Group, which forms the lowest stratigraphic unit in the district and hosts more than 85 known massive sulphide deposits. The Kristineberg deposit is situated lower in the Skellefte Group than most other deposits. It comprises three main ore zones: (1) massive sulphide lenses of the A-ore (historically the main ore), having a strike length of about 1,400 m, and extending from surface to about 1,200 m depth, (2) massive sulphide lenses of the B-ore, situated 100–150 m structurally above the A-ore, and extending from surface to about 1,000 m depth, (3) the recently discovered Einarsson zone, which occurs in the vicinity of the B-ore at about 1,000 m depth, and consists mainly of Au–Cu-rich veins and heavily disseminated sulphides, together with massive sulphide lenses. On a regional scale the Kristineberg deposit is flanked by two major felsic rock units: massive rhyolite A to the south and the mine porphyry to the north. The three main ore zones lie within a schistose, deformed and metamorphosed package of hydrothermally altered, dominantly felsic volcanic rocks, which contain varying proportions of quartz, muscovite, chlorite, phlogopite, pyrite, cordierite and andalusite. The strongest alteration occurs within 5–10 m of the ore lenses. Stratigraphic younging within the mine area is uncertain as primary bedding and volcanic textures are absent due to strong alteration, and tectonic folding and shearing. In the vicinity of the ore lenses, hydrothermal alteration has produced both Mg-rich assemblages (Mg-chlorite, cordierite, phlogopite and locally talc) and quartz–muscovite–andalusite assemblages. Both types of assemblages commonly contain disseminated pyrite. The sequence of volcanic and ore-forming events at Kristineberg is poorly constrained, as the ages of the massive rhyolite and mine porphyry are unknown, and younging indicators are absent apart from local metal zoning in the A-ores. Regional structural trends, however, suggest that the sequence youngs to the south. The A- and B-ores are interpreted to have formed as synvolcanic sulphide sheets that were originally separated by some 100–150 m of volcanic rocks. The Einarsson zone, which is developed close to the 1,000 m level, is interpreted to have resulted in part from folding and dislocation of the B-ore sulphide sheet, and in part from remobilisation of sulphides into small Zn-rich massive sulphide lenses and late Au–Cu-rich veins. However, the abundance of strongly altered, andalusite-bearing rocks in the Einarsson zone, coupled with the occurrence of Au–Cu-rich disseminated sulphides in these rocks, suggests that some of the mineralisation was synvolcanic and formed from strongly acidic hydrothermal fluids.

Paragenetic relationships and their implications for ore genesis at the Cannington Ag-Pb-Zn deposit, Mount Isa Inlier, Queensland, Australia

The Proterozoic Cannington Ag-Pb-Zn deposit in the Mount Isa inlier is hosted by a polydeformed sequence of quartzofeldspathic gneiss, pegmatites, amphibolites, quartzites, garnetiferous quartzites, sillimanite-garnet schists, and minor Fe-Mn silicate units that display close mineralogical and geochemical similarities to rocks hosting the Broken Hill deposit in New South Wales. The timing of mineralization at Cannington is controversial; premetamorphic and metamorphic-metasomatic models have been proposed. This paper aims to contribute to this debate from the point of view of paragenetic relationships on a deposit scale.Sulfide-bearing rocks include graphitic, Fe-Mn silicate, and siliceous types, based on differing mineral contents, metal zonation, and Fe, Mn, Pb, and Zn concentrations. Fe-Mn silicate and siliceous types are subdivided according to the relative proportions of Pb and Zn. Graphitic and quartz-rich, banded olivine-pyroxenoid types display laterally continuous, fine compositional banding over meter scales, and granoblastic sulfide-silicate textures with spheroidal sulfide inclusions in all silicates. Deformation is evidenced by D 2 structures such as folds, boudinage, sulfide-filled extensional veinlets and piercement veins, and the preferred alignment of graphite, biotite, ovoid garnet poikiloblasts, fayalite and pyroxmangite aggregates, and in some instances, sulfide grains. Quartz-poor olivine-pyroxenoid and hedenbergite types comprise contrasting brittle-ductile breccias with anastomosing D 2 mylonites in fluorite-rich zones. In fluorite-poor zones, granoblastic sulfide-silicate-magnetite textures predominate, with spheroidal sulfide inclusions in Fe-Mn silicates and magnetite. Quartz-rich, banded hedenbergite types are characterized by syn- to post-D 2 hedenbergite veins and associated hedenbergite-quartz-garnet alteration that overprints compositional banding in banded olivine-pyroxenoid types. The alteration is commonly localized around D 2 structures such as quartz-hedenbergite-garnet-carbonate-filled tension gashes. Siliceous Pb-Zn-Ag type is characterized by quartz veins and sulfidic breccias comprising nebulous, ragged clasts of silicified and weakly mineralized graphitic and, to a lesser extent, banded olivine-pyroxenoid types in a matrix of recrystallized sulfide. The siliceous Zn type consists of sulfidic breccias and quartz veins in strongly silicified metasediments. Quartz veins in siliceous Pb-Zn-Ag and Zn types display a syn-to post-D 2 timing.The paragenesis has been divided into pre- to synpeak metamorphic (stage I), syn- to postpeak metamorphic retrograde alteration (stage II), and near-surface hydrothermal alteration (stage III) assemblages. Stage II has been subdivided into high-grade anhydrous (stage IIa), high-grade hydrous (stage IIb) and low-grade hydrous (stage IIc) assemblages. Stage I peak metamorphic assemblages comprise anhydrous minerals in sulfide-bearing graphitic and olivine-pyroxenoid types. Granoblastic sulfide-silicate textures and spheroidal sulfide inclusions in stage I Fe-Mn silicates indicate that sulfides were present prior to metamorphism. Stage IIa retrograde syn- to post-D 2 hedenbergite veins and hedenbergite-quartz-calcic almandine alteration overprint stage I assemblages. Stage IIb retrogression involved post-D 2 amphibole alteration and minor sulfide deposition, and was followed by stage IIc pyrosmalite and pyrosmalite-magnetite alteration associated with abundant secondary sulfides, sulfosalts, and antimonides. Stage III involved quartz-carbonate-chlorite alteration temporally and spatially associated with D 4 subvertical faulting.The presence of premetamorphic sulfides indicates that the deposit has in part a premetamorphic origin. Subsequent modification during syn- to post-D 2 retrogression resulted in reworking and possible zone refining of the deposit via localized remobilization of sulfides. It is likely that exotic components were introduced during the retrograde stage by regional metasomatic fluids.

U-Pb dating of minerals in alteration halos of Superior Province massive sulfide deposits: syngenesis versus metamorphism

U-Pb geochronology of igneous zircon from rhyolitic host rocks to the Archean Kidd Creek, Geco and Winston Lake massive sulfide deposits, in the Superior Province of Ontario, shows that volcanism, which accompanied mineralization, occupied a narrow time span (2717±2 Ma, 2720±2 Ma and 2723±2 Ma, respectively). Precise ages of hydrothermal monazite, allanite and rutile from alteration zones surrounding the above deposits indicate that these minerals crystallized 40–70 million years after volcanism. Monazite from Kidd Creek mine is 2659±3 Ma old, in agreement with spatially associated 2664±25 Ma old rutile. Monazite from a biotite schist at Geoco mine gives a similar age of 2661±1 Ma. However, monazite from a sericite schist, which hosts the ore at Geco mine, is 2675±2 Ma old. Abraded large monazite grains from three units in the Winston Lake deposit are coeval with biotite crystallization and record an age of 2677±2 Ma, approximately the same as monazite in the sericite schist at Geco. Data points from allanite fractions from both the Winston Lake and Geco deposits fall on a Pb-Pb isochron that gives an age of 2672±5 Ma. Rutile from Winston Lake gives a younger age of 2651±6/-2 Ma and may date retrograde alteration of biotite to chlorite. The ca. 2676 Ma age of monazite from Winston Lake and in the sericite schist at Geco mine probably dates a regional metamorphic event that affected most of the southern Superior Province. The ca. 2660 Ma old monazite in the biotite schist at Geco mine and in the chlorite-sericite alteration at Kidd Creek may date later K-metasomatism caused by metamorphically derived fluids that were focussed along old fault structures. Such fluids were also responsible for local sulfide remobilization. Monazite and rutile are spatially associated with chlorite and sericite alterations at Kidd Creek. Their young ages indicate that these originally syngenetic mineral assemblages may have been significantly affected by regional metamorphism. Formation of monazite at all three deposits studied was a result of significant REE remobilization during metamorphism. The discrete character of syn-metamorphic hydrothermal activity in different units of the same deposit, as well as its synchroneity among different, widely separated deposits, requires a mechanism for episodic injection of heat and fluid into the crust on a regional scale. These activities are broadly coeval with, and probably related to, plutonism within adjacent metasedimentary subprovinces and middle to lower crustal metamorphism in the Superior Province.

Geology of the Bousquet 2 Mine; an example of a deformed, gold-bearing, polymetallic sulfide deposit

The Bousquet 2 mine is a deformed pyritic polymetallic Archean gold deposit located within a zone of intense ductile-brittle deformation composed of highly sheared and altered metamorphic tectonites of contrasting rheological properties. The ore occurs in a metamorphosed zone of aluminous alteration and is composed of foliation-parallel massive and semimassive pyritic lenses overprinted by late en echelon extensional veinlets containing Au-Ag-Cu mineralization.Structural and textural analyses show that the gold-bearing sulfide bodies and enclosing host rocks contain discrete tectono-metamorphic features resulting from two principal episodes of metamorphism, M 1 and M 2 . The earlier prograde event, M 1 , and coeval regional deformation, D 1 , were accompanied by overall ductile deformation of sulfides and by recrystallization and remobilization of the mineralization parallel to foliation. M 1 caused development of a pervasive east-west-trending metamorphic layering of the pyritic mineralization, transposition and elongation of the pyritic bodies parallel to mineral stretching L 1 lineations, meter-scale folding of sulfides, sulfide brecciation, coarsening and annealing recrystallization of pyrite, and ductile remobilization of incompetent sulfides and gold into interstices and triple-point junctions of juxtaposed pyrite grains. Extensive differential remobilization of ductile sulfides (mainly sphalerite, pyrrhotite, galena, chalcopyrite, chalcocite, and bornite) and gold took place during M 1 and gave rise to planar zones enriched in Au-Ag-Cu mineralization along the interfaces of pyritic lenses and their adjacent silicate rocks.M 2 metamorphism is chronologically related to a late brittle incremental stage of the progressive deformation and is characterized by high fluid influx, pervasive retrogression of peak metamorphic minerals, and remobilization of sulfides and gold into transgressive structures. The retrograde mineralization displays a wide range of small-scale structures resulting from fluid-assisted remobilization of ductile sulfides, including piercement and injection structures, as well as foliation-oblique extensional veinlets. Metamorphic remobilization of ore constituents took place mainly at ore-wall rock interfaces. Fe-, Pb-Zn-, and Au-Ag-Cu- bearing extensional veinlets generally occur in foliation-parallel protores of similar mineralogical composition and are interpreted as having resulted from in situ metamorphic remobilization.Gold and copper show a corelationship throughout the deposit; the highest gold and copper values occur within extensional veins overprinting previously Au-Cu-enriched planar zones. Mineralogical zoning in the sulfide masses is structurally controlled and can be related directly to abundant Au-Cu-bearing veinlets that represent mineralized segments of a systematic joint system.Structural and textural evidence suggests that gold mineralization with its present textural relations formed during M 1 and M 2 , but that a large proportion of the structurally controlled vein mineralization resulted from in situ remobilization rather than from additions from an external source.