Epithermal gold deposits part ii geology and gold deposits of the oatman district, northwestern arizona by ed dewitt, jon p. Epithermal veins tend not to have great vertical continuity, but many are exceedingly rich and deserving of the term bonanza. Unfortunately, the tonnage of ore in epithermal veins is typically small compared with other types of lower grade gold deposits. Portions of the host rock may either dissolve and be transported away or else react chemically with the circulating volatile fluids or the newly formed. Abstract epithermal gold deposits mehmet duyan supervisor. Hedenquist 2 bhp minerals international exploration, 229 shepherds bush road, london w6 7an, u. Recognising sinters in epithermal gold deposits surficial deposits of siliceous sinter are a com mon feature of presentday hot springs in areas of active volcanism, but they are rarely recognised in older, eroded volcanic ter ranes because of their low preservation poten. 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. The high and low sulphidation epithermal deposits associated with blue coloured belts are late mesozoic and cenozoic in age generally deposits located in the middle of plates grey coloured belts or metallogenic provinces are associated with paleozoic age ca. Gold remobilisation and formation of high grade ore shoots driven. Classification vs modeling each ore deposit is unique like a persons finger print this uniqueness arises out of.
They are the most numerous of all classes of deposit. Since the 1980s gold has started to gain popularity among mining. Porphyry and most epithermal deposits are hosted within magmatic arcs related to compressional subduction settings, while only some epithermal. In the group of arc low sulphidation gold deposits the term epithermal is only incorporated in the epithermal quartz gold silver deposits, which occur at highest crustal levels most removed from inferred intrusion source rocks, while the adulariasericite epithermal gold silver deposits are described above as rift low sulphidation. Smith2 abstract mines in the oatman mineralized district, near oatman in northwestern arizona, have produced more than 1. Dilational and contractional jogs along faultsshear zones. They contain economic concentrations from a precious metal such as gold and silver, and in some cases base metals such as copper, lead, iron ore and. Ore deposit is a natural concentration of one or more minerals within the host rock. Compared to epithermal deposits, mesothermal deposits have higher as, w, and auag values, higher co 2 content in fluid inclusions, and. Robust geochronological studies suggest that mesozoic epithermal gold mineralization is represented by the southeastern china fold belt scfb zhong et al. Multistage evolution of goldbearing hydrothermal quartz.
Map showing location of sedimenthosted gold deposits in the great basin province. Magmatic vapor contraction and the transport of gold from the porphyry environment to epithermal ore deposits. Epithermal gold silver and porphyry copper gold exploration short course manual greg corbett incomplete draft as at february 2018. Chemical mobility of gold in the porphyryepithermal. Gold tends to be concentrated in the vapor phase of fluids at high temperatures and pressures. Pdf geophysical exploration for epithermal gold deposits. Characteristics and origin of sedimenthosted disseminated gold deposits.
Lack of contact with retrograde, h 2 srich magmaticmeteoric waters may be a prerequisite for the preservation of early aurich porphyrystyle mineralization and may also explain the observed association between gold and hypogene iron oxide alteration in many porphyry deposits. Epithermal gold deposits styles characteristics an. Hydrothermal mineral deposits are those in which hot water serves as a concentrating, transporting, and depositing agent. Composition and origin of fluids associated with lode gold deposits. Epithermal gold deposits have size, geometry, and grade variations that can be broadly organized around some genetic classes and, therefore, influence the exploration approach or philosophy. Although the pongkor district has been the subject of several geological studies, the arc evolution in relation to gold mineralisation is less well understood. Other articles where epithermal deposit is discussed. A fascinating group and characteristic of epithermal gold deposits is that you can virtually see them forming today, simply by visiting hot springs.
Original paper epithermal gold mineralization in costa. Diagnostic features of epithermal gold deposits geological, mineralogical, and geochemical features of epithermal au deposits are listed for each of three deposit subtypes in table 2. Over twentytwo epithermal gold deposits have been currently explored, possessing a total resource of ca. Like the gold deposits in nevada and colorado, epithermal mineralization in the canadian cordillera. For best results viewing and printing pdf documents, it is recommended that you download the documents to your computer and open them with adobe reader. Celina and the mokrskoeast deposits figure 1, are hosted by volcanic rocks of. Among the numerous classifications that followed, one group of deposits clearly showed a common set of. Mineral deposit mineral deposit hydrothermal solution. Hydrothermal fluids forming epithermal gold deposits are ausaturated in most cases, whereas deposits of carlintype are auundersaturated. Dual origins of lode gold deposits in the canadian cordillera. Pdf mineral spectra associated with gold deposits researchgate. Models and exploration methods for major gold deposit types robert, f. Although they are a product of the same igneous system, low sulfidation epithermals gold deposits are very different from high sulfidation. This district hosts the largest gold vein deposits in java, indonesia.
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. These systems are formed within a vertical continuum from shallow epithermal environments to the upper portions of porphyry cuau deposits. Hydrothermal gold deposits epithermal, carlintype, and orogenic have accounted for 75% of lode gold production. Whether or not there is a direct temporal link betxveen oreforming. Characteristics of high sulphidation epithermal gold. Pdf gold deposits in greece are spatially associated with backarcarc. Pdf epithermal gold deposits of the southwest pacific. Distinctive features typically present include key alteration mineral assemblages low sulphidation. Characteristics of high sulphidation epithermal gold deposits of the miopliocene age volcanic belt, chile and argentina 2018. Representative examples are described of the following. Exploration for epithermal gold deposits gold in 2000. Models and exploration methods for major gold deposit types. Low sulfidation deposits on the other hand from a geothermal system in which the magmatic fluid is cooled and diluted by groundwater and the ph is neutralized at depth.
The pongkor epithermal gold mineralisation district is located approximately 80 km southwest of jakarta. Geophysical exploration for epithermal gold deposits. 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. However, sometimes the preexisting rock wall which contains the vein undergoes alteration. Pdf high sulphidation gold deposits a retrospective. Tantalizingly, in a number of hot springs, transitory redorange precipitates occur which are found to be ore grade in gold and silver and which carry a suite of elements as, sb, hg, tl now recognized as characteristic of epithermal gold deposits weissberg, 1969. Pdf compilation of the different alteration types associated with gold deposits. Vein deposits of this nature are a type of hydrothermal deposit because the mineral species which compose the veins were precipitated by hot waters. This photo is pamukkale, low sulfidation hot springs in turkey, with a beautiful white centre terraces. Two of three main ore bodies of the mokrsko gold deposit, the. Of these, the deposits in southern china are remarkably similar to nevada carlintype deposits and are interpreted to have formed where metamorphic fluids reacted with. High sulphidation epithermal gold deposits form in geothermal systems where hot acidic hydrothermal fluid directly from the intrusion, remains undiluted by ground water.
Epithermal deposits are responsible for 8% gold frimmel, 2008, 17% silver singer, 1995, and a certain amount of base metals production globally, being the important source of precious metals for mexico, the united states, canada, chile, peru, papua new guinea, and japan. Hyndman1 openfile report 01501 2001 prepared in cooperation with the usda forest service, pacific northwest region, okanogan. Hydrothermal deposits are never formed from pure water, because pure water is a poor solvent of most ore minerals. Epithermal gold mineralization in cretaceous volcanic belt. Although these deposits form in distinctly different geologic settings and by. Part or all of this report is presented in portable document format pdf. Epithermal gold and silver in newfoundland and labrador. Pdf epithermal gold deposits styles characteristics an. Epithermal gold deposits have size, geometry, oretype, and grade variations that can be broadly organized around some genetic classes and, therefore, influence the exploration approach or philosophy. Epithermal deposits typically form above the level of porphyry cuau deposits figure 4.
These have provided additional points of view and expanded the nomenclature surrounding the problem of gold deposit classification. High sulphidation gold systems are a unique and increasingly important type of mineral deposit. The auas and ausb associations are common in gold deposit. Assessment method for epithermal gold deposits in northeast washington state using weightsofevidence gis modeling by d. Like those with yellowstone in wyoming or rotorua in new zealand. Sedimenthosted gold deposits of the worlddatabase and grade. Gold mineralization occurs in the form of epithermal veins and. Magmatic vapor contraction and the transport of gold from. These three fluid inclusion populations point to three contrasting sources. Controls to low sulphidation epithermal auag mineralisation. In low sulfidation the main control for gold deposition, is fluid boiling caused by a drop in the confining pressures the.
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