Regional structures provide the main control on deposit distribution. Orogenic gold deposits, or gold deposits in metamorphic rocks, are the spatially and. Dr richard goldfarb is a world expert on orogenic gold deposits. Critical elements in carlin, epithermal, and orogenic gold. Histograms of fluidinclusion data from gold deposits, jamestown subdistrict 142 120. Nov 11, 2017 these deposits may be associated with magmatic intrusions like the previous deposits, but in this case, the intrusion is only a heat engine of fluid circulations. Alternative balanced solutions are available commercially under different brand names and composition may vary by preparation. Fluid inclusions provide valuable information on the pressure, temperature and fluid composition ptx of the environment of formation, hence understanding ptx properties of the fluid. First is magnetic surveys can be very useful exploration tools, when looking for bends and structures that the potential host greenstoneorogenic shear hosted gold deposits and mineralization. Fluid origin and structural enhancement during mineralization.
Advancing mineral exploration models for orogenic gold. Gold deposits of typically relatively low grade, which formed directly from fluid exsolution during granitoid emplacement within metamorphic rocks, are now also clearly recognized i. Most quartz veins in the shear zone, with and without gold mineralization, were boudinaged during progressive shear deformation with. Geochronological and stable isotope evidence for widespread orogenic gold mineralization from a deepseated fluid source at ca 2. These deposits form in response to major orogenic events caused by accretion or changes in subduction direction or dip. The term mesothermal veins is really a sack term, referring simply to the depth formation.
The paper presents analysis of the distribution of the principal parameters of mineralizing fluids depending on the age of the mineralization. Common or evolving fluid and metal sources through. A proposed classification in the context of their crustal distribution and relationship to other gold deposit types. Orogenic definition of orogenic by the free dictionary. Orogenictype coppergoldarsenicbismuth mineralization. A solid understanding of the composition of different types of fluids is essential to understanding the physiologic effects following administration and the appropriate clinical application. Gold deposits encyclopedia of life support systems. Geology, geochemistry, and genesis of orogenic goldantimony. Fluid inclusions provide valuable information on the pressure, temperature and fluid. Salier, brock and groves, david and mcnaughton, neal and fletcher, ian. Gold that is 24k is also called fine gold and is greater than 99. Distribution of orogenic gold deposits in relation to fault zones and gravity gradients. Schematic geologic map of boulder county gold district showing location of the most productive gold deposits 9 118.
Coupled hosr isotope composition of tourmaline and quartz documented. Many of these trace elements are commonly referred to as critical or nearcritical elements or metals and have been locally recovered. Orogenic gold deposits bohlke, 1982 dominantly form in metamorphic rocks in the mid to shallow crust 515 km depth, at or above the brittleductile transition, in compressional settings that facilitate transfer of hot gold bearing fluids from deeper levels goldfarb et al. Unique about the flatschach district is the lowertemperature overprint of copper arsenides domeykite and koutekite and. Diversity of gold deposits, geodynamics and conditions of. Gold mineralization is characterized by highgrade hydraulic breccias b and c ores that overprint an earlier tectonic breccia a ore. Some parameters of the fluids their salinity and pressure at orogenic gold. Vein, stockwork and disseminated gold deposits are very common within orogenic belts, providing a large percentage of total historical world and australian gold production. One evolving fluid sulfur isotopes vary but overlap 10. The source of the ore fluid and hence of the gold in orogenic lode gold deposits remains unreso lved. Moz resource formed during the late metamorphic uplift of a metasedimentary schist belt in southern new zealand.
Geological survey, box 25046, ms 964, denver federal center, denver, co 802250046, usa b state key laboratory of geological processes and mineral resources, school of earth sciences and resources, china university of geosciences, beijing 83, china. Scientific underpinings of orogenic gold presentation. The suite of elements depleted in mid to highgrade otago and alpine schists is almost identical to those enriched in the orogenic gold deposits in otago. The source of the ore fluid and hence of the gold in orogenic lode gold deposits remains unresolved. Pdf new constraints on fluid sources in orogenic gold deposits. Insights from the otago and alpine schists, new zealand article in economic geology 1018. Latekinematic timing of orogenic gold deposits and. In doing so, it will provide a more holistic view of gold deposit genesis. Orogenic gold deposits occur in many metamorphic belts, and metamorphism was typically accompanied by at least some magmatism groves et al.
The smartville block, also called the smartville ophiolite, smartville complex, or smartville intrusive complex, is a geologic terrane formed in the ocean from a volcanic island arc that was accreted onto the north american plate during the late jurassic 160150 million years ago. Archean orogenic lode gold deposits geoscienceworld books. Ore fluids are typically characterized by significant concentrations of. These deposits may be associated with magmatic intrusions like the previous deposits, but in this case, the intrusion is only a heat engine of fluid circulations. Physicochemical parameters and geochemical features of ore. Gold precipitation by phase separation and fluidrock reactions in narrow pt. Mesothermal and greenstone gold deposits aka orogenic. Orogenictype coppergoldarsenicbismuth mineralization at.
This 5day workshop is made up of a series of oneday courses taught by leading. Deposits can range from single small quartz veins to large and commonly highgrade, faultshear controlled systems containing in excess of 25 million ounces of gold. Various theories of ore genesis explain how the various types of mineral deposits. We invite contributions on all aspects of geochemistry applied to these intriguing deposits. Geochronological and stable isotope evidence for widespread. Noble gases fingerprint a metasedimentary fluid source in the. Indeed, both chloride and hydrocarbonate containing co 2 and ch 4 fluids were found in variable proportions up to the dominance of either the oxidized or the reduced. Hydrothermal alteration, ore fluid characteristics and. Mesothermal gold deposits form half way up through the rise of the melt from the deep crust to the surface usually at a depth of less than 10 km but greater than 1 km. On the source of orogenic gold geology geoscienceworld. The collision created sufficient crustal heating to drive mineralladen water up through numerous fissures.
Orogenic gold deposits are a widespread coherent group of epigenetic ore deposits that are sited in accretionary or collisional orogens. It is also reasonable to suggest that the ability of fluid at orogenic gold deposits to carry gold only insignificantly depends on the chemical composition of this fluid. With increased prominence, the orogenic gold model has often been cited as the status quo and is challenged by new findings, such as a strong local association with a particular igneous or sedimentary rock type or the identification of anomalous fluid characteristics at an individual deposit, that are presented in terms of their potential to overturn the standard model. Application of fluid inclusions in geological thermometry. Unique about the flatschach district is the lowertemperature. Pdf orogenic gold deposits of all ages, from paleoarchean to tertiary, show consistency. Orogenicmesothermalgreenstone gold deposits exploration. Apr 23, 2016 the worldclass macraes orogenic gold deposit. Val dor orogenic gold deposits formed by mixing of two fluids. How the various types of mineral deposits form within the earths crust. There is an ambient fluid carrying the carbon likely as methane. Fluid chemistry of orogenic lode gold deposits and implications for. How to explore or go prospecting for a orogenicmesothermalgreenstone gold deposit is described herein starting with what exploration tool can be used. Most quartz veins in the shear zone, with and without gold mineralization, were boudinaged during progressive shear deformation.
In contrast, information on element concentrations in low to moderate salinity i. Orogenic gold deposits are gold lodes within and associated with metamorphic belts 1,7,8,9. Application of fluid inclusions in geological thermometry andras fall abstract many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. This knowledge is used herein to develop a targeting model for orogenic gold deposits in the framework of a mineral systems approach cf. Orogenic gold deposits are the product of complex largescale processes which include the production of metalrich fluids, the transport of these metalrich fluids through the earths crust, and the.
This project represents an ambitious interdisciplinary effort to link geochemistry with crustalscale fluid migration, aiming specifically to improve mineral exploration success for orogenic gold deposits. Nature and source of the oreforming fluids associated with orogenic. Jun 20, 2010 the jinshan orogenic gold deposit is a worldclass deposit hosted by a ductile shear zone caused by a transpressional terrane collision during neoproterozoic time. Orogenic type copper gold arsenic bismuth mineralization at flatschach eastern alps, austria johann g. Orogenic gold deposits, also called mesothermal gold deposits are of great economic importance as they represent about 30% of world gold production. Your gold is really an alloy, or mixture of metals. Nature and source of the oreforming fluids associated. In both types of orogen, hydrated marine sedimentary and volcanic rocks have been added to continental margins during tens to some 100. This fluid composition consistency favors an ore fluid produced from a single source area and rules out mixing of fluids from multiple sources as significant in orogenic gold formation. Timing, nature and characteristics of orogenic gold deposits. Histograms of fluid inclusion data from gold deposits, jamestown subdistrict 142 120.
Seg workshop on ree resources, iocg systems, and gold. Noble gases fingerprint a metasedimentary fluid source in. Similarities in ore fluid compositions and controls on gold deposition are evident, despite regional variations in host rock composition and metamorphic grades. Methane is derived from heating any carbon source rock. Using orogenic gold deposits as an example, geostatistical techniques are. The otago and alpine schists of the south island of new zealand form a young epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar lowsalinity ore fluids and thermal conditions of metal transport and deposition. Carlin, epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar lowsalinity ore fluids and thermal conditions of metal transport and deposition. The process of mountain formation, especially by a folding and faulting of the earths crust. Nov 10, 20 dr richard goldfarb is a world expert on orogenic gold deposits. This fluid composition consistency favors an ore fluid produced from a single. Pdf fluid chemistry of orogenic gold lode deposits and.
However iv fluid bags are often labelled as glucose so only this term should be used. Ore bodies at the deposit include laminated quartz veins and disseminated pyritebearing mylonite. The leaching is most likely to have been caused by metamorphic fluid produced by dehydration reactions at the greenschistamphibolite boundary. Seg workshop on ree resources, iocg systems, and gold deposits in carlintype, epithermal, and orogenic environments june 1822, 2012 course description who should attend. Gold deposits can still be seen today forming in some active geothermal areas. Mineralising fluids, metals and metalloids were derived from within the metasedimentary host. The jinshan orogenic gold deposit is a worldclass deposit hosted by a ductile shear zone caused by a transpressional terrane collision during neoproterozoic time. Oreforming processes of the daqiao epizonal orogenic gold. Apart from low salinity h 2 oco 2 composition, other natural evidence in favor of the metamorphic source model comes from the remarkable similarity in h 2 s contents in fluid inclusions from orogenic gold deposits 0. Uniform ore fluid compositions in orogenic gold deposits of dharwar craton. Therefore, the regional data provide strong evidence for the involvement of sedimentary components in gold mineralisation, but are consistent with deeper. Estimated compositions of gold bearing hydrothermal fluids with respect to fluid oxidation state ah2 and sulfide content ah. The daqiao gold deposit is hosted in organicrich triassic pumpellyiteactinolite facies metamorphosed turbidites in the west qinling orogen, central china. Epigenetic gold deposits in metamorphic terranes include those of the precambrian shields approx 23,00025,000 t au, particularly the late archean greenstone belts and paleoproterozoic fold belts, and of the late neoproterozoic and younger cordilleranstyle orogens approx 22,000 t lode and 15,500 t placer au, mainly along the margins of gondwana, laurentia, and the more recent circum.
Geology, fluid inclusion, and isotope constraints on ore. Orogenic gold deposits bohlke, 1982 dominantly form in metamorphic rocks in the mid to shallow crust 515 km depth, at or above the brittleductile transition, in compressional settings that facilitate transfer of hot goldbearing fluids from deeper levels goldfarb et al. Our production chemistry testing includes the following areas. Orogenic fluid analysis laboratory offers a full suite of testing for optimizing your well performance and minimizing the operating expenditure. Mesothermal and greenstone gold deposits aka orogenic geology. Sources of metals and fluids in orogenic gold deposits.
Ores were formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens. Helium and argon extracted from fluid inclusions in sulphide mineral grains three crush extractions from one sample have crustal. In the above orogens, isotopegeochronological estimates suggest that the ore deposits were formed late in the orogenic history or even after orogeny had demonstrably ended 3,4,10,11. Orogenic article about orogenic by the free dictionary. Distribution of orogenic gold deposits in relation to fault. The role of saline fluids basemetal and gold mineralization at the cobalt hill prospect northeast of the sudbury igneous complex, ontario. The co n sensus that the ore fluid of orogenic deposits of all ages and settings is a low. Timing, nature and characteristics of orogenic gold deposits in the broken river province, ne queensland, australia i. Orogenic gold deposits of all ages, from paleoarchean to te rtiary, show consistency in chemical composition. He explains how orogenic gold formed during plate tectonic collisions and especially during continental growth. Distribution, character and genesis of gold deposits in. This 5day workshop is made up of a series of oneday courses taught by leading researchers in the fields of rare earth and precious metals. Lowsulfide quartz gold deposit model by lawrence j.
Minerals free fulltext physicochemical parameters and. A 4d geological model of the gto has previously been developed and constrained by integrated surface mapping, structural analysis, geochemistry and geophysical data detailed in joly et al. They are the products of aqueouscarbonic fluids, with typically 520 mol% co 2, although unmixing during extreme pressure fluctuation can lead to entrapment of much more co 2rich fluid inclusions in some cases. Highgrade gold ore from the harvard mine, jamestown, california, a wide quartzgold vein in californias mother lode. Geology, geochemistry, and genesis of orogenic gold.
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