The Angouran deposit (19.3 Mt at 23.4% Zn and 4% Pb) is the second-largest Zn-Pb deposit in Iran. The deposit is hosted in a Neoproterozoic−Cambrian marble-schist sequence within a breccia pipe in a domal structure, with sulfide mineralization under low-temperature hydrothermal conditions (<200 ºC). The features of the ore-hosting breccias are similar to known halokinetic diapir breccias in the world but evaporite minerals are subtle. The common types of breccia clasts in the Angouran breccia pipe include a matrix-supported angular clast (float breccia) with highly variable sizes and orientations and exotic volcanic clasts. The volcanic clasts were derived from the underlying Miocene volcanic rocks, evidenced by the consistent petrography and zircon U-Pb ages dated at 20−19 Ma. Abundant smithsonite pseudomorphs after anhydrite and anhydrite inclusions within sphalerite and pre-ore marcasite in the breccia matrix indicate that the breccia pipe contains abundant anhydrite prior to the Zn-Pb mineralization. The enrichment of evaporite is also supported by the occurrence of considerable double-terminated quartz crystals that contain spherical and tabular carbonate inclusions and anomalously high Li, Na, and K concentrations, relatively high B concentration, and high δ18O values (up to 28.3‰). These observations suggest the Angouran deposit formed in a former halokinetic diapir breccia pipe. The halokinetic diapirism was possibly triggered by thrust loading of the marble-schist sequence over the Miocene evaporite beds during the Arabia-Eurasia continental collision. Halokinetic structures elsewhere in the Angouran region warrant this consideration. Most of the evaporite minerals in the breccia pipe were dissolved and replaced before and/or during subsequent Zn-Pb sulfide and smithsonite mineralization events. This study provides a good example for the identification of vanished evaporites, halokinetic structure, and associated Mississippi Valley-type mineralization.

The Paleoproterozoic Mârmorilik Formation in the Karrat basin of West Greenland hosts the Black Angel Zn–Pb deposit. Chlorine-rich scapolite, zones with vuggy porosity and quartz nodules in the ore-bearing marble are herein interpreted to represent metamorphosed, vanished, and replaced evaporites, respectively. Mineralization is closely associated with anhydrite with δ 34 S values (5.2–12.6‰) broadly comparable to published values for Paleoproterozoic seawater sulfate. Considering the fundamental attributes of the mineralization and host sequence, a Mississippi Valley-type (MVT) model is the most obvious explanation for mineralization. Overlying the ore-bearing sequence are organic-rich semipelites and massive calcitic marbles, which may have served as seals for hydrocarbon or reduced sulfur and acted as chemical traps for deposition of the sulfidic ore. The Mârmorilik Formation contained an interlayered sulfate-rich evaporite-carbonate sequence, a common setting for MVT deposits in the late Neoproterozoic and Phanerozoic, but unique among the few known MVT deposits in the Paleoproterozoic. This ca. 1915 Ma evaporite-carbonate platform is younger than sulfate evaporites deposited during and immediately after the ca. 2220–2060 Ma Lomagundi carbon isotope excursion and records a significant seawater sulfate level during a time interval when it was assumed that it had been too low to form extensive evaporite deposits. Therefore, MVT and clastic-dominated (CD) Zn–Pb deposits in the geological record might progressively fill the apparent gap in marine sulfate evaporites and provide unique insights into Proterozoic seawater sulfate level. Considering the sequence of tectonic events that affected the Karrat basin, the mineralization took place between Nagssugtoqidian collision (< 1860 Ma) and Rinkian metamorphism (ca. 1830 Ma).

The Bougrine Zn-Pb sulfide deposit (5.5 Mt @ 12 % Zn + 2.5 % Pb) in the Eastern Maghreb salt diapir province of Tunisia is located at the northeastern end of the Lorbeus-Bougrine diapir. The several-km large diapir is composed of Triassic evaporite that intruded about 10 km-thick Jurassic and Cretaceous marine sedimentary rocks during the Cretaceous and Tertiary. Mineralization occurs in breccia zones at the contact with the Triassic diapir and in the peridiapiric Cretaceous strata. Most of the ore is stratabound (F2 orebody) with microsphalerite disseminations in organic-rich laminated black limestone of the Cenomanian-Turonian Bahloul Formation, where sphalerite occurs as infill of Globigerina shells, as massive replacement of Globigerina-rich layers, as banded colloform sphalerite and in voids as euhedral, coarse-grained crystals together with skeletal galena and minor marcasite. Abundant degraded oil seepages in the orebodies and their host rocks testify to the existence of a (former) hydrocarbon reservoir.The various sphalerite generations have highly variable Mn and Fe contents; Cd has an average content of 445 ppm; As and Hg contents are in the 200 ppm range; Tl content is about 40 ppm; Ga content is about 10 ppm; and In content is consistently <1 ppm. Fluid inclusions in celestite, coarse-grained late-stage sphalerite and calcite indicate moderate fluid salinities (16 +/- 2 wt% NaCl eq.) and moderate temperatures (85 to 146 degrees C). The empirical trace-element sphalerite geothermometer gives 184 +/- 38 degrees C for the main-stage microsphalerite and the banded colloform sphalerite which have no measurable fluid inclusions.A wide range of delta C-13 (-13.6 to 5.6 parts per thousand) and delta O-18 (-19.8 to 33 parts per thousand) values is observed in ore-stage and post-ore calcite. Ore-stage calcite commonly has negative delta C-13 values reflecting involvement of carbon from organic matter; its delta O-18 composition with an average of 22.6 +/- 2 parts per thousand (19.7 to 26.0 parts per thousand) may be explained by a moderate-temperature hydrothermal fluid. There is no systematic delta S-34 variation between and across the different styles of mineralization. The range of delta S-34 of 6-19 parts per thousand with a mean of 13 parts per thousand is close to the delta S-34 value of local and regional Triassic marine sulfate (delta S-34 = 16 parts per thousand). Thermochemical reduction of Triassic sulfate, likely mediated by hydrocarbons, is the most probable source for sulfur in the ores. Lead isotope data on galena are within a narrow field of upper crustal signature (Pb-206/Pb-204 = 18.71-18.77; Pb-207/Pb-204 = 15.66-15.70; Pb-208/Pb-206 = 38.81-38.97) indicating a homogeneous ore fluid.The major characteristics of the Bougrine ore deposit are typical of Mississippi Valley type Pb-Zn deposits and indicate large-scale fluid circulation likely related to stacking and uplift in the northern Tunisian Nappes Zone during the Miocene. Both the hydraulic load of meteoric water and over-pressured basinal and basement fluids during compressional movements favored southward fluid migration along basement discontinuities and most permeable strata in the Mesozoic-Cenozoic sedimentary pile. Low-pressure domains around salt diapirs in a rifting environment allowed focused upward fluid flow, and the hydrocarbon reservoir of the Bahloul Formation then provided the geochemical trap for efficient base metal deposition.

This study evaluates the effect of organic matter impurities on pyrite Re-Os dating, using the giant Jinding sediment-hosted Zn-Pb deposit in China as an example. The Jinding deposit is hosted in a Paleocene evaporite dome that was a hydrocarbon reservoir before mineralization. Pyrite in Jinding formed in two stages: pre-ore (py1) and syn-ore (py2). Two types of py1 are recognized, organic matter-free and organic matter-bearing. The organic matter-free py1 contains homogeneously distributed low concentrations of Re (<2.5 ppb) that yields an isochron age of 51 ± 1 Ma (mean square of weighted deviates [MSWD] = 3.2). This date is interpreted to be the age of py1 formation. The organic matter-bearing py1 contains organic matter inclusions trapped during py1 growth and synchronous with bacterial reduction of sulfate. Elemental mapping with laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) shows that the organic matter inclusions have Re signals 1 to 4 orders of magnitude higher than those of pyrite, revealing that organic matter is the major host for Re. Such pyrite separates contain 37 to 1,145 ppb Re. The Re-Os data of organic matter-bearing py1 yield an isochron age of 72.9 ± 0.5 Ma (MSWD = 0.2). This age is older than the actual py1 formation age of 51 ± 1 Ma but overlaps with previously dated bitumen Re-Os isochron age of 68 ± 5 Ma at Jinding, indicating that organic matter inclusions can significantly influence the Re-Os dates of pyrite and likely other sulfides. This study demonstrates that in order to date sulfides formed in organic-rich environments using the Re-Os method, it is necessary to determine the distribution of Re in samples using detailed petrography and LA-ICP-MS trace element mapping plus spot analysis.

The Xitieshan Pb-Zn deposit in the North Qaidam orogenic belt, contains a geologic resource of 64 million tons grading 4.86 percent Zn and 4.16 percent Pb. The mineralized zones are hosted by the Tanjianshan Group, a metamorphosed succession of volcanic-sedimentary rocks in a Middle to Late Ordovician back-arc basin. Lower greenschist to middle amphibolite facies metamorphism and deformation of the original Xitieshan Pb-Zn ores and host rocks resulted in zones hosted in marble and schist. Sulfides in the marble consist of pyrite, sphalerite, galena, and marcasite with accessory chalcopyrite with undeformed textures that reflect the original carbonate replacement mineralization. Pyrrhotite, pyrite, sphalerite, and galena are the major sulfides in the schist-hosted ores, which occur as laminated sulfide layers that pinch, swell, and conform to the foliation of the schist. The schist-hosted mineralization occurs as a remobilized paragenetic assemblage that reflects the recrystallization and physical migration of the original sulfides across the brittle-ductile boundaries of these minerals during dynamic metamorphism. The sulfur isotopic compositions of ore-stage sulfides cluster around values of -1 parts per thousand to +5 parts per thousand, consistent with sulfur derived from leaching volcanic rocks in the host sequence, or magmatic-related fluids. Carbon, oxygen, and strontium isotope patterns of the altered marble (delta C-13 = -3.8 to -1.5 parts per thousand, delta O-18 = 8.7 to 12.2 parts per thousand, and Sr-87/Sr-86 = 0.713092 to 0.713503) indicate extensive isotopic exchange with hydrothermal fluids. Gangue minerals, including ankerite and siderite, intergrown with sulfides at Xitieshan have C, O, and Sr isotopic compositions (delta C-13 = -1 to +1.7 parts per thousand, delta O-18 = 2.3 to 7.8 parts per thousand, and Sr-87/Sr-86 = 0.715707 to 0.722918) and textures indicative of replacement reactions between an originally marine carbonate rock and magmatic-related hydrothermal fluids. Considering the Xitieshan ore fluids replaced carbonate in a volcanoclastic sequence together with the similarities of host rocks, mineralogy, alterations, and sulfur isotope composition, the most likely genetic model for the deposit is an intrusion-related carbonate replacement deposit that underwent subsequent metamorphism and deformation.

The Shalipayco Zn–Pb deposit, in central Peru, is composed of several stratabound orebodies, the largest of which are the Resurgidora and Intermedios, contained in carbonate rocks of the Upper Triassic Chambará Formation, Pucará group. Petrography suggests that a single ore-forming episode formed sphalerite and galena within vugs, open spaces, and fractures. Three-dimensional (3D) geological modeling has allowed division of the Chambará Formation into four members (Chambará I, II, III, and IV) that better define lithological controls on sulfide formation. Diagenetic replacement of evaporite minerals with the organic matter (OM) presence likely generated secondary porosity and H2S accumulation by bacterial sulfate reduction (BSR), providing ground preparation for the later Zn–Pb mineralizing event. The least-altered host rocks have C–O isotope compositions of 1.8 ± 0.1‰ (VPDB) and 29.9 ± 2.1‰ (VSMOW), respectively, within the Triassic marine carbonate ranges. Early dolomite contains lighter C–O composition (1.1 ± 0.9 and 23.8 ± 2.9‰, respectively) consistent with OM decomposition during burial diagenesis. Post-mineralization calcite has still lighter C–O composition (− 5.1 and 13.3‰, respectively), suggesting meteoric water that had migrated through organic-rich strata. The strontium isotopes of Mitu group basalts (0.709654–0.719669) indicate it as a possible, but not the unique source of strontium and probably of other metals. Highly negative sulfide sulfur isotope values (− 23.3 to − 6.2‰ (VCDT)) indicate a major component of the ore sulfur derived ultimately from BSR. However, multiple lines of evidence suggest that preexisting H2S underwent thermochemical redox cycling prior to ore formation. The influx of hot metalliferous brines to dolomitized zones containing trapped H2S is the preferred model for ore deposition at Shalipayco.

Abstract Sediment-hosted Zn-Pb and Cu deposits in China include Mississippi Valley-type (MVT) deposits, clastic-dominated (CD) deposits (also historically called sedimentary-exhalative [SEDEX] deposits by some workers), sandstone-hosted (SSH) Zn-Pb deposits, a few large magmatic-related carbonate-replacement deposits (CRD), and volcanic-hosted massive sulfide (VHMS) deposits that have been mistakenly classified as nonmagmatic-related MVT or CD deposits. There are also areas of China that contain important sediment-hosted copper (SHC) deposits. China is exceptionally endowed with MVT deposits with three of the five largest MVT deposits in the world (Huoshaoyun, Jinding, and Changba-Lijiagou). In contrast, China has one CD deposit (Dongshengmiao) in the top 30 CD deposits in the world. The few SHC deposits are small relative to world-class examples. The largest SHC deposits are located in the Yangtze and the North China cratons and hosted in Proterozoic rocks with indications of massive halokinetic features like those observed in the African copper belt. The MVT ores are most abundant in the Yangtze block, Qinling orogen, and the central and eastern Himalayan-Tibetean orogen. There are many other carbonate-hosted deposits in the North China craton and the Cathaysia block that have been widely classified as MVT or sedimentary-exhalative deposits. These are better classified as CRD or skarn deposits based on their proximity to intrusions, alteration assemblages, trace and minor element signatures, and, in some deposits, the presence of skarns minerals. Numerous sediment-hosted Zn-Pb deposits in China have been traditionally classified as SEDEX or syngenetic deposits based on laminated ore textures and stratiform ores that we interpret to reflect deformation and selective replacement processes rather than synsedimentary ore processes. Only two of these sediment-hosted deposits can be unequivocally classified as CD deposits: Dongshengmiao and Tanyaokou in the Langshan area of the North China craton. They are hosted in a siliciclastic-dominated sequence of a Proterozoic passive margin. The location and genesis of many MVT and SHC deposits in China are directly controlled by evaporites and evaporite facies. Evaporite and evaporite facies had an extremely important role in determining the location of the MVT deposits. The second largest sediment-hosted Zn-Pb deposit in China and fifth largest in Asia, Jinding in the Himalayan-Tibetan orogenic belt, is hosted in a hydrocarbon-reduced sulfur reservoir that formed because of salt diapirism. Other large sediment-hosted Zn-Pb MVT deposits in China that are interpreted to be controlled by structures produced by evaporite diapirism are Daliangzi and Tianbaoshan in the western Yangtze block. The largest Zn-Pb deposit in China is the newly discovered oxidized Huoshaoyun Zn-Pb MVT deposit, also in the Himalayan-Tibetan orogenic belt that is hosted in an evaporite-bearing sequence. The third largest Zn-Pb resource in China is at the Changba-Lijiagou deposit and, together with numerous smaller deposits, define a belt of metaevaporites in a carbonate platform sequence of the northern Yangtze platform. Other evaporite-related MVT ores include the Huize deposits that are hosted in a former Carboniferous evaporite-bearing hydrocarbon reservoir and the extensive Sinian dolostone-hosted Zn-Pb deposits that reflect evaporite dissolution breccias in the Yangtze block. The Tarim craton in northwestern China contains the only significant SSH deposit at Uragen. The ore zone lies in the footwall of an evaporative unit that may have served as a hydrocarbon and reduced sulfur trap. Furthermore, the most significant SHC deposits are hosted in Proterozoic rocks in the North China craton and the Yangtze block that contain extensive halokinetic breccias and structures.

The Florida Canyon evaporite-related Zn-Pb sulfide deposit, in northern Peru, is one of the largest Mississippi Valley-type deposits in South America. Triassic carbonate and former evaporite-bearing rocks of the Pucará Group host the orebodies that constitute two different styles: (1) predominantly stratabound ore associated with hydrocarbon-rich porous dolostones and evaporite dissolution breccias and (2) high-grade ore associated with evaporite breccias representing diapiric injections along faults. A dome structure that controls the location of the ore deposit was defined by drill hole spatial data; the dome likely resulted from halokinetic processes during Andean deformation. NNE-trending, steeply dipping secondary faults linked to major northwest structures appear to control the distribution of ore grades in the deposit. Mineralization postdated hydrocarbon migration and accumulation. Strontium, carbon, and oxygen data isotope signatures allow distinction between pre- and synmineralization carbonate stages. The sulfur isotope composition of sulfides in the deposit suggests they precipitated as the result of mixing of a metal-rich fluid with resident hydrogen sulfide in the dome. Local thermochemical sulfate reduction may have contributed to the reduced sulfur budget during mineralization.

Many discoveries of large deposits in the United States, including the Carlin, Mountain Pass, Henderson, Red Dog, and Eagle deposits, were based in part on U.S. Geological Survey (USGS) geologic, geochemical, or geophysical data. The Mineral Resources Program contributes to exploration success by (1) providing geologic, geochemical, and geophysical data; (2) developing mineral deposit models that target permissive areas; and (3) developing techniques that are used by industry in exploration. Basic geoscience data, particularly USGS geological maps, form the foundation for mineral exploration. Development and refinement of deposit models impact how exploration is focused. Two models that significantly changed based on USGS research include orogenic gold and sediment-hosted Pb-Zn. The new data from these models have changed exploration strategies. Indirect contributions by the USGS include development of techniques, such as the initiation of fluid inclusion research in the 1950s, and the development of geochemical and geophysical techniques that play a major role in exploration programs. The USGS also has contributed directly to exploration through collaborative studies with industry in well-known districts in the United States.

Some sediment-hosted base metal deposits, specifically, the clastic-dominated Zn-Pb deposits, carbonate-hosted Mississippi Valley-type (MVT) deposits, sedimentary rock-hosted stratiform copper deposits, and carbonate-hosted polymetallic ("Kipushi-type") deposits, are or have been important sources of critical elements including Co, Ga, Ge, PGEs, and Re. Cobalt is noted in only a few clastic-dominated and MVT deposits, whereas sedimentary rock-hosted stratiform copper deposits are major producers. Gallium occurs in sphalerite from clastic-dominated and MVT deposits. Little is reported of germanium in clastic-dominated deposits; it is more commonly noted in MVT deposits (up to 4,900 ppm within sphalerite) and has been produced from carbonate-hosted polymetallic deposits (Kipushi, Tsumeb). Indium is known to be elevated in sphalerite and zinc concentrates from some MVT and clastic-dominated deposits, produced from Rammelsberg and reported from Sullivan, Red Dog, Tri-State, Viburnum Trend, Lisheen, San Vincente, and Shalipayco. Platinum and palladium have been produced from sedimentary rock-hosted stratiform copper deposits in the Polish Kupferschiefer. Sedimentary rock-hosted stratiform copper deposits in the Chu-Sarysu basin are known to have produced rhenium. Although trace element concentrations in these types of sediment-hosted ores are poorly characterized in general, available data suggest that there may be economically important concentrations of critical elements yet to be recognized.

The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian–Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ∼110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the evaporation of seawater to halite saturation and requires a dilution of more than two times by meteoric water. The higher K/Na values in fluid inclusions from barite suggest that the brines interacted with K-rich rocks in the basement or siliciclastic sediments in the basin. Carbonate gangue minerals (ankerite and calcite) have δ 13 C and δ 18 O values that are close to the carbonate host rock and indicate fluid equilibrium between carbonate host rocks and hydrothermal brines. The δ 34 S values for sphalerite and galena fall within a narrow range (1 to 10 ‰) with a bulk value of 7.5 ‰, indicating a homogeneous source of sulfur. The δ 34 S values of barite are also relatively homogeneous (22 ‰), with 6 ‰ higher than the δ 34 S of local and regional Triassic evaporites (15 ‰). The latter are believed to be the source of sulfate. Temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of Triassic sulfate via hydrocarbons produced probably from Late Cretaceous source rocks. The 87 Sr/ 86 Sr ratio in the Bou Jaber barite (0.709821 to 0.711408) together with the lead isotope values of Bou Jaber galena ( 206 Pb/ 204 Pb = 18.699 to 18.737; 207 Pb/ 204 Pb = 15.635 to 15.708 and 208 Pb/ 204 Pb = 38.321 to 38.947) show that metals were extracted from homogeneous crustal source(s). The tectonic setting of the Bou Jaber ore deposit, the carbonate nature of the host rocks, the epigenetic style of the mineralization and the mineral associations, together with sulfur and oxygen isotope data and fluid inclusion data show that the Bou Jaber lead-zinc mineralization has the major characteristics of a salt diapir-related Mississippi Valley-type (MVT) deposit with superimposed events of fluorite and of barite deposition. Field relations are consistent with mineral deposition during the Eocene–Miocene Alpine orogeny from multiple hydrothermal events: (1) Zn-Pb sulfides formed by mixing of two fluids: one fluid metal-rich but reduced sulfur-poor and a second fluid reduced sulfur-rich; (2) barite precipitation involved the influx of a meteoric water component that mixed with a barium-rich fluid; and (3) fluorite precipitated from a highly saline fluid with higher temperatures.

The Jinding Zn–Pb sediment-hosted deposit in western Yunnan, China, is the fourth largest Zn deposit in Asia. Based on field observations of the ore textures, breccias, and the sandstone host rocks, the ores formed in a dome that was created by the diapiric migration of evaporites in the Lanping Basin during Paleogene deformation and thrust loading. Most of the ore occurs in sandstones that are interpreted to be a former evaporite glacier containing a mélange of extruded diapiric material, including breccias, fluidized sand, and evaporites that mixed with sediment from a fluvial sandstone system. A pre-ore hydrocarbon and reduced sulfur reservoir formed in the evaporite glacier that became the chemical sink for Zn and Pb in a crustal-derived metalliferous fluid. In stark contrast to previous models, the Jinding deposit does not define a unique class of ore deposits; rather, it should be classified as MVT sub-type hosted in a diapiric environment. Given that Jinding is a world-class ore body, this new interpretation elevates the exploration potential for Zn–Pb deposit in other diapir regions in the world.

The formation of base metal sulfide deposits requires not only a source of metals but also reduced sulfur. If incoming sulfur is present in ore fluids as sulfate, then a source of electrons is needed to drive the reduction of sulfate to sulfide. The oxidation of organic matter can release electrons that provide the reducing capacity, whether it be in low- or high-temperature settings that are conducive to biological or thermochemical sulfate reduction (BSR or TSR). The amounts of organic matter reacted and sulfide minerals formed can be estimated by mass balance calculations. In this study, an integrated mass balance expression is formulated that takes into account the sulfide mineral content and organic carbon content and H/C ratios of mineralised and non-mineralised rocks. Model calculations based on carbon, sulfur and redox budget balances suggest that the extent of oxidation of the organic matter present at the Here’s Your Chance (HYC) Pb–Zn deposit is insufficient for reduction of the required quantity of sulfate. The results imply that externally derived reducing capacity and/or reduced sulfur is required to form the metal resource. Possible sources include hydrocarbon-rich fluids from deeper parts of the sedimentary sequence or formation of sulfide and organic matter as products of BSR during sedimentation/early diagenesis. However, the observed oxidation of organic matter associated with the deposit suggests that at least some reducing capacity is locally derived. Therefore, our calculations are consistent with genetic models for HYC that have multiple sources of redox budget for sulfate reduction.

Acta Geologica Sinica - English EditionVolume 88, Issue s2 p. 174-175 Meeting Abstracts Evaporites and Mississippi Valley-Type Zn-Pb-Ag Deposits: An Evolving Perspective David LEACH, Corresponding Author David LEACH Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037 China Centre for Exploration Targeting, University of Western Australia, Perth 6009Corresponding author. E-mail: dleach5100@gmail.comSearch for more papers by this author David LEACH, Corresponding Author David LEACH Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037 China Centre for Exploration Targeting, University of Western Australia, Perth 6009Corresponding author. E-mail: dleach5100@gmail.comSearch for more papers by this author First published: 29 December 2014 https://doi.org/10.1111/1755-6724.12369_15Citations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume88, Issues2Special Issue: Meeting Abstracts: The 14th Quadrennial International Association on the Genesis of Ore Deposits Symposium. August 19–22, 2014, Kunming, ChinaDecember 2014Pages 174-175 RelatedInformation

Banded iron formations (BIF) are the protolith to most of the world's largest iron ore deposits. Previous hypogene genetic models for Paleoproterozoic "Lake Superior" BIF-hosted deposits invoke upwards, down-temperature flow of basinal brines via complex silica and carbonate precipitation/dissolution processes. Such models are challenged by the necessary SiO2 removal. Thermodynamic and mass balance constraints are used to refine conceptual models of the formation of BIF-hosted iron ore. These constraints, plus existing isotope and halogen ratio evidence, are consistent with removal of silica by down- or up-directed infiltration of high-pH hypersaline brines, with or without a contribution from basinal brines. The proposed link to surface environments suggest that Paleoproterozoic BIF-ore upgrade may provide a record of a critical time in the evolution of the Earth's biosphere and hydrosphere.

President Enders, members and guests: Thank you for being here this evening and my great appreciation to Rich Goldfarb for his usual unusual colorful and entertaining citation. I am greatly humbled to be included among the past recipients of the SEG Penrose Medal. I do not have the words to adequately convey my enormous appreciation to SEG for this great honor. I find it remarkable that a kid from rural South-side Virginia, born into a working class family—none of whom even thought of attending a university—would be so fortunate to be standing before you tonight. It is customary for recipients of the Penrose Medal to reflect upon one’s past accomplishments and the exceptional people who collectively produced the science that underlies the consideration for the Penrose Medal. I will of course do this, but my journey to this award is about a few very special people who gave beyond the expected to help and encourage me along my journey. There were some dedicated teachers and professors who gave me confidence in myself and planted the seeds of scientific curiosity and the joy of discovery. And most importantly, I have been truly blessed with an exceptional family: my children and grandchildren who missed me at some important times in their lives, some birthdays and soccer games and visits by the tooth fairy. However, my wife, Susan, really deserves the medal more than anyone. While I was working long hours at the office and traveling to see “the rocks,” she was at home being an exceptional mother, grandmother, and the live-in “handyman” whose job description also included changing the beeping smoke alarm batteries in the middle of the night—which seem to have an uncanny sense of when I am away. My mother was a hard-working southern lady who instilled in me an …

The Mississippi Valley-type deposits of the Touissit-Boii Beker district are hosted by a 25 in diick sequence of diagenetically and hydrothermally dolomitized carbonate plat fOrm rocks of Attlenian-Bajocian age. fide mineralization consists principally of galena and sphaleritc and occurs its open-space fillings of voids and moderate 10 massive replacement of the medium- to coarse-grained host dolostone. Five types of dolomite have been distinguished, two of winch (D-1, and D-2) are of replacement origin, whereas HD1, HD2, HD3 occm-ring tts Open-space filling itre of hydrothermal tffili tt on I till ore controls include strtitigrtiphy and lithology, carbonate (iissolution, paleogeography, faults or faulted rocks, and availability of organic matter.Fluid inclusion data, along with Na-C1-Br leachatc, indicate that the ore-lOrtning fluids correspond to evolved NaCl-CaCl2-KCl-MgCl2 basin-derived hot (100 degrees +/- 20 degrees C) saline brines (>20 wt % NaCl equiv) that acquired their higli salinities and Ca/Na ratios through evaporation of seawater, tun' subse(pielit dolomitization and fluid-rock interactions. Stable isotope data fOr replacement :cud hydrothermal dolomites are tightly clustered and overlapping, with 6180 imd. 613 degrees C values from 20.5 to 21.2 and 0.2 to 0.7 parts per thousand, respectively. Similarly, sulfides yield 634S values between 11.2 and 1.9%0, W1 IC reati those corresponding to the nearby Triassic g)7psum chister yield around 14%o. Altogether, these isotopic compositions are consistent with a hasinal-type Ilind with reduced sulfur very likely being derived through thermochemical reduction of dissolved sulfate, resulting ni metal precipitation, and carbon of mainly marine Aalenian-Bajocian carbonate origin with a minor biogenic component.Sr-87/Sr-86 values of replacement dolostone arc similar to those of ore-related hydrothermal dolomites, ranging from 0.70746 to 0.70833 and from 0.70769 to 0,70828, respectively, and are different from those of the Viscan rhvodacite (0.71849-0.72167). Lead isotope ratios (Pb-206/Pb-204) = 18.319-18.390, (PbPh)-Pb-207-Ph-204 = 15.620-15.680; Pb = 38.4,52-38.650) of sulfides are consistent with Ph being derived from the Visean rhyoditeite and associated volcaniclastic rocks. The intimate link between faults and mineralization suggests the strong possibility of brine ling regitnial-scale fttults tind N \\I-SW -trending local-settleow dung faults. The data suggest that MVT mineralization was emplaced during the late Neogene-Quaternary (i.e., ca. 15-1) Ma), possibly as a result of subsurface gravity-driven fluid flow in response to the collision between the African and Eurasian plates.

The Wallace 1° x 2° quadrangle folio includes a series of mineral resource appraisal maps prepared under the Conterminous United States Mineral Resource Assessment Program (CUSMAP). Also included in this folio are a variety of maps that present geochemical, geological, and geophysical data that were used to arrive at the mineral resource appraisal for the quadrangle. The geochemical maps, compiled from data collected by the U.S. Geological Survey in the Wallace quadrangle from 1978 through 1981, show the distribution and abundance of related elements and delineate areas with anomalous concentrations. The geochemical survey consisted of the collection and analysis of 1,229 samples of stream sediment and 1,080 samples of nonmagnetic heavy-mineral concentrates. A complete tabulation of the geochemical data used in the Wallace CUSMAP study is available on computer tape from the National Technical Information Service (McDanal and others, 1982). The data are also available, together with various statistical estimates, in U.S. Geological Survey OpenFile Report 82-494 (Leach and others, 1982). Maps showing the distribution and abundance of many of the· data are shown in many U.S. Geological Survey reports (Leach and Goldfarb, 1986; Leach and others, 1983 a, b, c, d, e, f; Leach and Hopkins, 1986 a and b; Leach and Domenico, 1985 and 1986).