Pdf mesothermal gold deposits

Mesothermal deposits form at intermediate depths, temperatures, and pressures. Gold mineralisation stage fluids range from magmatic to dominantly magmatic with variable amounts of external or unexchanged waters, probably introduced into the hydrothermal system during cooling. Apr 19, 2020 also described are the different ways that gold deposits form including placer deposits, mesothermal deposits, banded iron formation deposits, epithermal gold silver deposits, intrusion related brecciahosted deposits, and byproduct gold. The first is epithermal gold deposits associated with magmatic rocks, the second is epithermal gold deposits associated with sedimentary rocks carlintype and the third is epithermal gold. Potter a research school of earth sciences, the australian. Geological survey reston, va 20192 deposits in this class have been widely described and given many names. Mcqueen crc leme, australian national university, canberra, act 0200 and school of rehs, university of canberra, act 2601. Temperatures may range from 200 to 300 celsius during the formation of such deposits. Typically, epithermal deposits are younger than their enclosing or host rocks. Nov 10, 20 dr richard goldfarb is a world expert on orogenic gold deposits. Although, the mineralization at sabodala has drawn the attention of some workers sylla and ngom 11, gueye et al. Though scarce, gold is concentrated by geologic processes to form commercial deposits of two principal types. Characteristically, these faulthosted vein deposits exhibit a mixed brittleductile style of deformation discrete shears and vein fractures as well as a schistose shearzone fabric developed under greenschist facies metamorphic conditions. This quest has been driven by academic and industry needs to understand the apparently irregular pattern of distribution of orogenic lode gold deposits and the complexity of the processes controlling concentrations.

Quartz and carbonate minerals such as calcite caco 3, ankerite cafeco 3 2, siderite feco 3, dolomite camgco 3 2, and rhodocrosite mnco 3 occur in mesothermal depos. Jul 12, 20 epithermal gold deposits are among the richest gold deposits in the world with some bonanza grade ore shoots containing more than gt gold, or in other words, a kilogram of gold for every tonne of rock mined. Sixteen common types of bedrock gold deposits are distinguished from one another and their main geological attributes are. Harraz department of geology, faculty of science, tanta university, tanta, egypt. Many mesothermal gold quartz deposits are localized along highangle reverse or reverseoblique shear zones within greenstone belt terrains. Detailed examples from around the world are given for each type of gold deposit. They are localised along or adjacent to major structural crustal breaks or suture zones, related to terrane collisional boundaries. Epithermal gold for explorationists paper 200201, april 2002 5 mineralogical differences used to categorise the styles of low sulphidation epithermal gold deposit styles corbett and leach, 1998.

Comments on genesis although still regarded as controversial, intrusion related gold deposits irgd. Formation of oreshoots in mesothermal goldquartz vein. Within the host volcanosedimentary sequences at the province scale, worldclass orogenic gold deposits are most commonly located in. 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. Phillips, 20, continues largely because it is difficult to reliably identify the source of gold. The term mesothermal veins is really a sack term, referring simply to the depth formation. A rational geological classification of the commonly recognized lode gold deposits is feasible if it is based on the geological settings of the deposits, host rocks, nature of mineralization and geoche mical signature. Mesothermal lode gold deposit central belt peninsular malaysia. Mesothermal, in this context, may be inaccurate in that the deposit may have formed under a number of temperature and pressure. Pdf mesothermal gold veins and metamorphic devolatilization. Highangle reverse faults, fluidpressure cycling, and. These products are companions to the openfile report 4896. Gold deposits of canada, a database comprising referenced and detailed geological, geographical and economical information on 128 gold deposits, and to the openfile report 4894. One of the largest undeveloped gold projects in the world.

Jiang, department of geology, the university of newcastle, callaghan, new south. The deposit is typical of lode gold deposits in an archean setting, although other terms have been used. Lowsulfide quartz gold deposit model by lawrence j. What controls gold distribution in archean terranes. Mackenzie geology department university of otago po box 56 dunedin 9054, new zealand dave. He explains how orogenic gold formed during plate tectonic collisions and especially during continental growth. Gold is relatively scarce in the earth, but it occurs in many different kinds of rocks and in many different geological environments. Debate on the genesis of socalled orogenic gold deposits 75% of gold recovered through history. Mesothermal and greenstone lode gold deposits part 4 worldethq. Mesothermal lode gold deposit central belt peninsular malaysia 317 table 1 gives the malaysia s production of raw gold between 2006 and 2009, indicated over 90% of gold production is originated from pahang penjom gold mine since 1996, avocet mining plc, and recently from selinsing gold mine monument mining limited, and. Pdf comparison between orogenic or mesothermal gold. Mesothermal gold mother lode type homestake type lowsulfide quartz gold goldonly deposits quartzcarbonate lode gold.

The largescale migration of fluids through the continental crust has been well documented, but there is no consensus regarding the timing. Smith2 abstract mines in the oatman mineralized district, near oatman in northwestern arizona, have produced more than 1. The lodes are hosted in mafic and ultramafic volcanic rocks, banded iron. Part 4 of andrew jacksons informative series on ore deposits for those interested in economic geology. Hydrothermal alteration styles in ancient and modern orogenic.

Compared to epithermal deposits, mesothermal deposits have higher as, w, and auag values, higher co 2 content in fluid inclusions, and. Nn2002, fluid inclusions in the mesothermal gold deposit at atud mine, eastern desert, egypt. Dual origins of lode gold deposits in the canadian cordillera. Epithermal deposits typically form above the level of porphyry cuau deposits figure 4. Comparison of decrepitation, microthermometric and. On the source of orogenic gold geology geoscienceworld. Both of the latter designations may be criticized as too general. Primary gold deposits in portugal mesothermal or epithermal. Remaining inground gold resources in the province are estimated at 280 million ounces. Hydrothermal alteration styles in ancient and modern orogenic gold deposits, new zealand d. Deformational and metamorphic processes in the formation of. Box 28503, addis ababa, ethiopia 2department of geological sciences, university of vienna, althanstrasse 14, a1090 vienna, austria received december 31, 2003. Evidence of midoligocene hydrothermal activity in the northwestern alps.

Gold has historically been a key strategic commodity, and the study of gold deposit formation has long been investigated. The four deposits have a total identified mineral resource of. Rapid dewatering of the crust deduced from ages of. Like the gold deposits in nevada and colorado, epithermal mineralization in the canadian cordillera. Ore deposits 101 part 4 mesothermal and greenstone lode gold. Geochemistry, alteration, and genesis of gold mineralization in the okote area, southern ethiopia debele j. Origin and evolution of the um egat and dungash orogenic gold.

Mesothermal vein gold deposits investing news network june 2nd, 2016 mesothermal veins are known for their large size and continuation to depth, and therefore, are a major source of the world. Mesothermal deposits green lode gold deposits consists of gold bearing quartz lodes found in late archean and mesozoics greenstone belts. New approach of structural setting of gold deposits in. Mesothermal and greenstone gold deposits aka orogenic. Mesothermal and greenstone gold deposits aka orogenic geology. Epithermal gold deposits part ii geology and gold deposits of the oatman district, northwestern arizona by ed dewitt, jon p. Unfortunately, the tonnage of ore in epithermal veins is typically small compared with other types of lower grade gold deposits.

Gold in british columbia kerr sulphurets mitchell ksm owned and operated by seabridge gold inc. Although the term mesothermal gold quartz vein deposits implies formation at intermediate depths, recent models of the origin of these deposits vary as to the fluid source cf. Gns science, private bag 1930, dunedin 9054, new zealand. Epithermal gold and silver in newfoundland and labrador.

Geochemistry, alteration, and genesis of gold mineralization. Ker rich, 1989, such that magmatic, metamor phic, and meteoric fluids are all suggested as possibilities for quartz and metal transport. Gold deposits and gold districts of canada, a postersize map of canada showing the location and size of. Zoned alteration haloes are a feature of lode and vein gold. The resulting goldbearing quartz veins are emplaced over a unique depth range for hydrothermal ore deposits, with gold deposition from 1520 km to the near surface environment. The largescale migration of fluids through the continental crust has been well documented, but there is no consensus regarding the timing of fluid migration relative to orogenic episodes, or.