Nov 10, 20 dr richard goldfarb is a world expert on orogenic gold deposits. 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. Orogenic gold deposits can form over a variety of depths, from as. White mica 40ar39ar geochronology from goldrich quartz veins by aldo izaguirre,1,2 michael j. Timing, nature and characteristics of orogenic gold. Most genetic hypotheses for orogenic gold deposits that involve nearsurface or. Short course on orogenic gold in africa and worldwide. Orogenic gold deposits of all ages, from paleoarchean to tertiary, show consistency in chemical composition. Timing, nature and characteristics of orogenic gold deposits. One of the critical learning points you should walk away with from this talk. Fluid inclusions of orogenic gold deposits in the zhongchuan. The origin and hydrothermal mobilization of carbonaceous.
Models and exploration methods for major gold deposit types. Orogenic gold deposits are one of the worlds main groups of gold deposits that provide a source of gold 1, etc. Critical elements in carlin, epithermal, and orogenic gold. Goldfarbb, liang zhangb aorebusters pty ltd, gwelup 6018, western australia, australia b state key laboratory of geological processes and mineral resources, china university of geosciences, beijing 83. The focus of the mining operation is a model, which is often based on incomplete or flawed data.
Controls on the distribution of invisible and visible gold. Gold deposits free download as powerpoint presentation. The main objective of this report is to present the sample locations, 40ar39ar experimental methodology, and ar39ar isotopic data tables 14. Such deposits are thus the largest, single genetic. The gold resources of mauritania presently include two important deposits and a series of poorly studied prospects. Well greenstones shears hosted gold deposits are an important source of gold and there are lots of juniors out looking for them. Richard goldfarb, kunfeng qiu china univeristy of geosciences, beijing, china, email. This workshop on orogenic gold will be held at the university of cape town from february 2 to 3, 2019, the weekend prior to the mining indaba meeting. Orogenic, or the socalled mesothermal, gold deposits are a distinctive class of mineral deposit e. Exploration targeting for orogenic gold deposits in the granitestanami orogen. Author links open overlay panel alireza almasi a mahyar yousefi b emmanuel john m. There are six worldclass settings for magmatichydrothermal gold deposits. Orogenic gold mineralization in the qolqoleh deposit. Prospectivity analysis of orogenic gold deposits in saqezsardasht goldfield, zagros orogen, iran.
Pdf orogenic gold deposits are the main source of gold for humanity. Orogenicmesothermalgreenstone gold deposits exploration. An orebody is commonly a poorly understood geological entity, and the resource model is generated from samples taken from this orebody. Gold occurs in a wide range of deposit types and settings, but this paper is concerned with deposits in which gold forms the main economic commodity or a coproduct. Orogenic gold deposit model vein, stockwork and disseminated gold deposits are very common within orogenic belts, providing a large percentage of total historical world and australian gold production.
Gold is mostly invisible in solid solution or in the sulfide lattice, with minor visible gold associated with stibnite and in quartzcalcite veins. Orogenic gold deposits of china society of economic. Contrasting geochemistry of orogenic gold deposits in yukon. Mineral system analysis, targeting model and prospectivity analysis. Orogenic gold deposits account for an estimated 75% of the gold extracted by humans phillips 20, including the tonnage of witwatersrand, the worlds largest district. Pdf parameters for the formation of orogenic gold deposits.
Gacmac 2016 whitehorse field trip guide book, 82 p. The ores are widely recognized in both phanerozoic mobile belts and older cratonic blocks. Within the mining industry, all phases of the operation are dependent on the resource model. Macraes orogenic gold deposit new zealand origin and. On the source of orogenic gold geology geoscienceworld. Ores were formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens. The socalled mesothermal gold deposits are associated with regionally metamorphosed terranes of all ages. It also documents the key features of this spectacular deposit for a wide range of professionals in the resource geology community. This book describes the nature and origin of the macraes gold deposit. These deposits formed from the archaean to phanerozoic at crustal depths of more than 4 km. Orogenic gold deposits driving interest in canadian gold. The key parameters accounting for their formation remain under discussion. Orogeny, or mountain formation, is the result of intense upward.
Orogenic deposits are the source of much of the worlds gold. The objectives of this paper are to provide an update on gold deposit models, and what new approaches and techniques can now be used to find gold deposits. Physicochemical parameters and geochemical features of ore. The process of mountain formation, especially by a folding and faulting of the earths crust. Orogenictype coppergoldarsenicbismuth mineralization at. Orogenic gold deposits are the main source of gold for humanity. The macraes mine is the only modern mine in otago, and is therefore the only deposit to provide a window into the deeper parts of a mineralised system below the. Termed the tapajosparima orogenic belt by santos 1999, this goldrich crustal block is the probable product of compressional tectonism along part of the craton margin between about 2. Trace element composition of scheelite in orogenic gold deposits. Here is a look at the components that make up orogenic deposits. Hydrothermal alteration styles in ancient and modern orogenic. Typical correlation for orogenic gold deposits worldwide.
Consistent geological characteristics include deformed and variably metamorphosed. Trace element composition of scheelite in orogenic gold. Australian geologist daintree, studying the layers of gold, wrote into 1866. As all of the deposits studied in this thesis are classified as archaean orogenic gold deposits, the specific conclusions may only be pertinent to this style of mineralisation. When compared to other orogenic gold provinces goldfarb et al. Jurassic mineralization in the ytt occurred during convergent orogenesis and stacking of previously. The laramide caborca orogenic gold belt of northwestern sonora, mexico. Pdf invisible gold paragenesis and geochemistry in. Orogenic definition of orogenic by the free dictionary. Mineral potential tracts for orogenic, carlinlike, and. A proposed classification in the context of their crustal distribution and relationship to other gold deposit types, authordavid i. Six orogenic gold deposits constitute the yangshan gold belt in the west qinling orogen. Timing, nature and characteristics of orogenic gold deposits in the broken river province, ne queensland, australia i.
A holistic model for the origin of orogenic gold deposits and its. Phillips and powell either as the erosion of primary gold deposits or from hydrothermal accumulation. Based on available resource data, hodgson 1993 estimated that the 28 deposits. Such low levels of as is rare in most orogenic gold deposits. Archean orogenic lode gold deposits are the result of large, complex mineralizing systems that have developed within many archean terrains.
Camps show a characteristic variation in size hodgson, 1993 with most of the production coming from worldclass 100 t au and a few giant 500 t au deposits. Parameters for the formation of orogenic gold deposits. Common or evolving fluid and metal sources through time. Dr richard goldfarb is a world expert on orogenic gold deposits. Gold deposits can still be seen today forming in some active geothermal areas. 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. Both belts host orogenic gold deposits of mainly jurassic to early cretaceous age. The laramide caborca orogenic gold belt of northwestern. This field trip visits the most significant mineral deposits in northern southeast alaska and begins and ends with regional transects in the interior. This worldclass gold deposit has been a spectacular geological and economic success story, as.
Many of these trace elements are commonly referred to as critical or nearcritical elements or metals and have been locally. The origin and hydrothermal mobilization of carbonaceous matter associated with paleoproterozoic orogenictype gold deposits of west africa. Input data for the present study are existing gold deposits, mapped and interpreted faults, and multiscale. The term mesothermal veins is really a sack term, referring simply to the depth formation. The term orogenic gold deposit was defined by groves et al. Orogenic lodegold deposits were emplaced at about 1. Mineralizing systems are defined to include all geologic factors that control the generation and preservation of mineral deposits and emphasize the processes responsible for deposit formation at a variety of scales. Hydrothermal gold mineralization at the hira buddini gold mine, india. 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. Volcanogenic massive sulphide and orogenic gold deposits in northern southeast alaska. The relationship of the auag telluride event to orogenesis is not clear from these samples.
Prospectivity analysis of orogenic gold deposits in saqez. Orogenic gold deposits are associated with regionally metamorphosed terranes of middle archaeantertiary age goldfarb et al. Aspects of resource geology in archaean orogenic gold deposits. These deposits form in response to major orogenic events caused by accretion or changes in subduction direction or dip. Hydrothermal gold deposits epithermal, carlintype, and orogenic have accounted for 75% of lode gold production. Mesothermal and greenstone gold deposits aka orogenic. In contrast to typical orogenic gold deposits displaying textures indicating brittleductile deformation and recrystallization, those of grass valley only display minor brittle fracturing of quartz and pyrite. Distribution of orogenic gold deposits in relation to. Mesothermal and greenstone gold deposits aka orogenic geology. They are the products of aqueouscarbonic fluids, with typically 520mol\% co2, although unmixing during extreme pressure fluctuation can lead to entrapment of much more co2rich fluid inclusions in some cases. Even within this single style of mineralisation, different resource evaluation approaches are needed for each orebody. A scaleintegrated exploration model for orogenic gold deposits.
The twoday course will focus on the geology of and exploration for orogenic gold deposits, the. The idea that gold concentrations are derived from host rock as the source of gold in deposits in central victoria, is not new. Implications for exploration of worldclass and giant deposits david i. Distribution of orogenic gold deposits in relation to fault. For orogenic gold deposits at deeper crustal levels, oreforming fluids are commonly focused along. Pdf exploration targeting for orogenic gold deposits in. He explains how orogenic gold formed during plate tectonic collisions and especially during continental growth.
Knoxrobinson a, juhani ojala c, stephen gardoll a, grace y. The country rocks hosting the deposits are predominantly of devonian age with low. Jurassic mineralization in the ytt occurred during convergent. Orogenic gold deposits account for an estimated 75 percent of the gold extracted by humans, including the tonnage of witwatersrand, the worlds largest district such deposits are thus the. Detailed textural and traceelement analysis of sulfides in terms of a newlyerected paragenetic sequence for these deposits, together with previously. Carlintype gold deposits in nevada, usa, although characterized by aqueouscarbonic. 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. That then is a quick summary of greenstone orogenic shear hosted gold deposits. Prospectivity analysis of orogenic gold deposits in saqezsardasht goldfield demonstrated, however, that the ssz has a nwse trend, considering the spatial distribution pattern of known gold deposits in the study area, a nesw trend can be recognized for the mineralization events. Depositscale structural controls on orogenic gold deposits. Orogenic gold, or gold deposits in metamorphic rocks, and associated placer deposits, comprise. Latekinematic timing of orogenic gold deposits and.
Focus paper structural geometry of orogenic gold deposits. Supergene gold mobility in orogenic gold deposits, otago schist, new zealand 5 ore, and a substantially greater proportion of that nearsurface gold was free particles fig. The producing guelb moghrein deposit occurs along a shear zone in. 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. For these systems, the initial premise is that the structural or deformationrelated controls on dilation.
A proposed classification in the context of their crustal distribution and relationship to other gold deposit types. Archean orogenic lode gold deposits tend to occur in clusters within mining camps, defined as areas of about 100 km 2. Potential for new gold deposit discoveries in the palaeozoic miogeosynclinal sedimentary sequences of the tasman geosyncline on both sides of the tasman a province known for its orogenic style turbidite. Although these deposits form in distinctly different geologic settings and by. Conceptbased orogenic gold exploration requires a scaleintegrated approach using a robust mineral system model. Ores were formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and. 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. Detailed material for this globally important deposit type will be provided on tectonic and structural controls. Gold deposits encyclopedia of life support systems. Hydrothermal alteration styles in ancient and modern orogenic gold deposits, new zealand. Orogenic gold deposits, or gold deposits in metamorphic rocks, are the spatially and temporally most widespread gold deposit type, defining important exploration targets in precambrian shields and in phanerozoic orogen ic belts.
Glennie lake mapping and general comments on orogenic gold in. Scheelite from 25 representative orogenic gold deposits from various geological settings was investigated by epma electron probe microanalyzer and laicpms laser ablationinductively coupled plasmamass spectrometer to establish discriminant geochemical features to constrain indicator mineral surveys for gold exploration. Ftb2 volcanogenic massive sulphide and orogenic gold. Predictive targeting in australian orogenicgold systems. The late timing of orogenic gold deposits within the structural evolution of the host orogen implies that. Contrasting geochemistry of orogenic gold deposits in. Deposits can range from single small quartz veins to large and commonly highgrade, faultshear controlled systems containing in excess of. The inherent variation caused by geological complexity. Over the last century this class of gold deposit has been known by many different names like mesothermal gold deposits, metamorphic gold, goldonly, lode gold, shearzone hosted, structurally controlled and a host of other names including greenstonehosted and turbidite hosted deposits. I had long ago come to the conclusion, that most, if not all, the gold in the. Vein, stockwork and disseminated gold deposits are very common within orogenic belts, providing a large percentage of total historical world and australian gold production.