A review of the sediment-hosted, disseminated precious metal deposits of Nevada : geological setting, classification, genesis and exploration
- Authors: Ash, Philip John
- Date: 1986
- Subjects: Ore deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4906 , http://hdl.handle.net/10962/d1001566
- Description: Carlin-type, fine-grained, "invisible" or Disseminated Replacement Type gold-silver deposits are all different names for a major new type of ore deposit that is currently being extensively developed in the Western United States. This type of deposit is now being found elsewhere. Thus a descriptive empirical model that emphasizes the geological and geochemical environment of formation is needed to assist the mining industry in the search for similar deposits. These deposits are typically formed in carbonaceous, silty dolomites and Iimestones or mineralization calcareous siltstones rocks and is exceedingly fine-grained is disseminated in the and claystones. host sedimentary Gold-silver , ore. Primary alteration usually less than one micron in size in unoxidized types include decalcification, argillitization, silicification resulting in the and pyritization. Silicification is commonly intense formation of jasperoid bodies which may be the host to higher grade ore. Supergene alteration is dominated by oxidation resulting in the formation of numerous oxides and sulphates and the release of gold from its association with sulphides and organic carbon. elements are As, Ba, Hg, Sb, and TI. Commonly associated trace Available geological, geochemical, fluid inclusion and stable-isotope studies lead to the conclusion that a circulating hydrothermal system is the important factor necessary for gold-silver concentration and deposition. A direct genetic or only casual relation between are deposition and discrete igneous formations remains unclear. However, it is considered that volcanism provided the source of heat necessary for the generation of a circulating hydrothermal system. High angle faults and fold structures facilitate transport and are of prime importance in directing are fluids to favourable host lithologies. The host rocks, overwhelmingly carbonate - rich, include those whose original and/or altered compositions and resulting permeability provide favourable sites for the precipitation of disseminated gold. The processes specialized. resulting Any th ick in the formation of these deposits are section of carbonate rocks has the potential not to produce Disseminated Replacement Type deposits wherever underlying igneous activity has developed a hydrothermal system
- Full Text:
- Date Issued: 1986
- Authors: Ash, Philip John
- Date: 1986
- Subjects: Ore deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4906 , http://hdl.handle.net/10962/d1001566
- Description: Carlin-type, fine-grained, "invisible" or Disseminated Replacement Type gold-silver deposits are all different names for a major new type of ore deposit that is currently being extensively developed in the Western United States. This type of deposit is now being found elsewhere. Thus a descriptive empirical model that emphasizes the geological and geochemical environment of formation is needed to assist the mining industry in the search for similar deposits. These deposits are typically formed in carbonaceous, silty dolomites and Iimestones or mineralization calcareous siltstones rocks and is exceedingly fine-grained is disseminated in the and claystones. host sedimentary Gold-silver , ore. Primary alteration usually less than one micron in size in unoxidized types include decalcification, argillitization, silicification resulting in the and pyritization. Silicification is commonly intense formation of jasperoid bodies which may be the host to higher grade ore. Supergene alteration is dominated by oxidation resulting in the formation of numerous oxides and sulphates and the release of gold from its association with sulphides and organic carbon. elements are As, Ba, Hg, Sb, and TI. Commonly associated trace Available geological, geochemical, fluid inclusion and stable-isotope studies lead to the conclusion that a circulating hydrothermal system is the important factor necessary for gold-silver concentration and deposition. A direct genetic or only casual relation between are deposition and discrete igneous formations remains unclear. However, it is considered that volcanism provided the source of heat necessary for the generation of a circulating hydrothermal system. High angle faults and fold structures facilitate transport and are of prime importance in directing are fluids to favourable host lithologies. The host rocks, overwhelmingly carbonate - rich, include those whose original and/or altered compositions and resulting permeability provide favourable sites for the precipitation of disseminated gold. The processes specialized. resulting Any th ick in the formation of these deposits are section of carbonate rocks has the potential not to produce Disseminated Replacement Type deposits wherever underlying igneous activity has developed a hydrothermal system
- Full Text:
- Date Issued: 1986
Discordant bodies of postcumulis, ultramafic rock in the upper critical zone of the Bushveld complex : iron-rich ultramafic pegmatite bodies at Amandelbult and the Driekop platiniferous ultramafic pipe
- Authors: Scoon, Roger N
- Date: 1986
- Subjects: Ultrabasic rocks -- South Africa -- North-western Transvaal Pegmatites -- South Africa -- North-western Transvaal Platinum ores -- South Africa -- North-western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4930 , http://hdl.handle.net/10962/d1004912
- Description: From the abstract: In the layered sequence of the Bushveld Complex a number of distinct, but possibly genetically related groups of transgressive, postcumulus, ultramafic and mafic rock are recognised. The main part of this thesis investigates a suite of postcumulus rocks for which the name iron-rich ultramafic pegmatite is proposed. The majority of iron-rich ultramafic pegmatite bodies examined are from the upper critical zone of the layered sequence at Rustenburg Platinum Mines Amandelbult Section, in the northern sector of the western Bushveld Complex. Field relationships imply that the iron-rich ultramafic pegmatites should be considered as an integral feature of the layered sequence, even though they transgress the cumulates. Consequently, this thesis also includes a study of the cumulate sequence at Amandelbult. A second group of postcumulus, ultramafic rocks which is investigated comprises latiniferous ultramafic pipes; the Driekop pipe has been selected as a case study. This thesis is presented in four sections, namely, an introduction and verview, and studies on the Driekop pipe, the cumulate sequence at mandelbult and the iron-rich ultramafic pegmatite suite. A new classification scheme of discordant bodies of postcumulus, ultramafic rock in he Bushveld Complex is proposed (see also Viljoen & Scoon, in press). In he scheme presented here, two main varieties of postcumulus, ultramafic rock re recognised, namely, non-platiniferous magnesian dunites and iron-rich ltramafic pegmatites.
- Full Text:
- Date Issued: 1986
- Authors: Scoon, Roger N
- Date: 1986
- Subjects: Ultrabasic rocks -- South Africa -- North-western Transvaal Pegmatites -- South Africa -- North-western Transvaal Platinum ores -- South Africa -- North-western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4930 , http://hdl.handle.net/10962/d1004912
- Description: From the abstract: In the layered sequence of the Bushveld Complex a number of distinct, but possibly genetically related groups of transgressive, postcumulus, ultramafic and mafic rock are recognised. The main part of this thesis investigates a suite of postcumulus rocks for which the name iron-rich ultramafic pegmatite is proposed. The majority of iron-rich ultramafic pegmatite bodies examined are from the upper critical zone of the layered sequence at Rustenburg Platinum Mines Amandelbult Section, in the northern sector of the western Bushveld Complex. Field relationships imply that the iron-rich ultramafic pegmatites should be considered as an integral feature of the layered sequence, even though they transgress the cumulates. Consequently, this thesis also includes a study of the cumulate sequence at Amandelbult. A second group of postcumulus, ultramafic rocks which is investigated comprises latiniferous ultramafic pipes; the Driekop pipe has been selected as a case study. This thesis is presented in four sections, namely, an introduction and verview, and studies on the Driekop pipe, the cumulate sequence at mandelbult and the iron-rich ultramafic pegmatite suite. A new classification scheme of discordant bodies of postcumulus, ultramafic rock in he Bushveld Complex is proposed (see also Viljoen & Scoon, in press). In he scheme presented here, two main varieties of postcumulus, ultramafic rock re recognised, namely, non-platiniferous magnesian dunites and iron-rich ltramafic pegmatites.
- Full Text:
- Date Issued: 1986
Molybdeunum mineralization with emphasis on porphyry systems genesis and exploration
- Authors: Puig-Pichuante, R M
- Date: 1986
- Subjects: Molybdenum , Porphyry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5023 , http://hdl.handle.net/10962/d1006840
- Description: Mo became very important in the last century, because of its sophisticated properties and its use in the new technology of alloys . Porphyry systems (porphyry Cu-Mo and Mo) contribute a significant proportion (90 - 95 per cent) to the Mo world's production. This type of deposit is associated mainly with Phanerozoic orogenic belts. Above 87per cent of the world resources are in the American Circumpacific belts , both Andean and Cordilleran . Ore grade in porphyry Cu-Mo range from 0,005 to 0,04per cent Mo, whereas in porphyry Mo grades range from 0,08 to 0,75per cent Mo . These deposits are associated with a magmatism which shows an evolution from calcic in island arcs, to calc-alkaline in magmatic back arcs, with an increase of the Mo content in the same direction. Porphyry Mo deposits display several features in common with porphyry Cu deposits. hydrothermal Similarities include nature of host alteration patterns and distribution of rock intrusives, ore minerals. An interesting difference is found in the Re contents of the molybdenite mineral. This element is higher in the molybdenites of porphyry Cu, than in those of the porphyry Mo. The ore genesis process begins involves partial melting, within enriched zones of the upper mantle and magma differentation, liquid state thermogravitational diffusion, magma convection and boiling. These processes progressively concentrate Mo in the fluids, which are released at some stage, into sulphidic hydrothermal systems, under complex geologictectonic conditions involving fracturing, brecciation and hydrothermal alteration. Major concentrations of the ore mineral are always associated with potassic alteration, and with late magmatic-early hydrothermal stages (Chilean and Western North American porphyries). Geological mapping and a close understanding of alteration and mineralization patterns, and lithogeochemistry are important tools for the exploration of porphyry Mo deposits. Geochemical prospecting, using soils, vegetation and water as sampling media, and regional aeromagnetic, gravity surveys, aerial photography and remote sensing, are us.
- Full Text:
- Date Issued: 1986
- Authors: Puig-Pichuante, R M
- Date: 1986
- Subjects: Molybdenum , Porphyry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5023 , http://hdl.handle.net/10962/d1006840
- Description: Mo became very important in the last century, because of its sophisticated properties and its use in the new technology of alloys . Porphyry systems (porphyry Cu-Mo and Mo) contribute a significant proportion (90 - 95 per cent) to the Mo world's production. This type of deposit is associated mainly with Phanerozoic orogenic belts. Above 87per cent of the world resources are in the American Circumpacific belts , both Andean and Cordilleran . Ore grade in porphyry Cu-Mo range from 0,005 to 0,04per cent Mo, whereas in porphyry Mo grades range from 0,08 to 0,75per cent Mo . These deposits are associated with a magmatism which shows an evolution from calcic in island arcs, to calc-alkaline in magmatic back arcs, with an increase of the Mo content in the same direction. Porphyry Mo deposits display several features in common with porphyry Cu deposits. hydrothermal Similarities include nature of host alteration patterns and distribution of rock intrusives, ore minerals. An interesting difference is found in the Re contents of the molybdenite mineral. This element is higher in the molybdenites of porphyry Cu, than in those of the porphyry Mo. The ore genesis process begins involves partial melting, within enriched zones of the upper mantle and magma differentation, liquid state thermogravitational diffusion, magma convection and boiling. These processes progressively concentrate Mo in the fluids, which are released at some stage, into sulphidic hydrothermal systems, under complex geologictectonic conditions involving fracturing, brecciation and hydrothermal alteration. Major concentrations of the ore mineral are always associated with potassic alteration, and with late magmatic-early hydrothermal stages (Chilean and Western North American porphyries). Geological mapping and a close understanding of alteration and mineralization patterns, and lithogeochemistry are important tools for the exploration of porphyry Mo deposits. Geochemical prospecting, using soils, vegetation and water as sampling media, and regional aeromagnetic, gravity surveys, aerial photography and remote sensing, are us.
- Full Text:
- Date Issued: 1986
Vein and replacement type Sn and Sn-W mineralization in the Southern Kaoko Zone, Damara Province, South West Africa/Namibia
- Authors: Petzel, V
- Date: 1986
- Subjects: Geology, Structural -- Namibia -- Damara Mobile Belt , Geology, Structural -- Namibia -- Kaoko Belt , Veins (Geology) -- Namibia -- Damara Mobile Belt , Veins (Geology) -- Namibia -- Kaoko Belt , Mineralogy -- Namibia -- Damara Mobile Belt , Mineralogy -- Namibia -- Kaoko Belt , Geodynamics -- Namibia -- Damara Mobile Belt , Geodynamics -- Namibia -- Kaoko Belt
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5041 , http://hdl.handle.net/10962/d1007633
- Description: The ENE trending Brandberg West - Goantagab Sn-W belt is located in the Southern Kaoko Zone of the northern coastal branch of the Damara Orogen. The lithologies in this area are turbiditic and consist of three schist units separated by two marble horizons, all of which are correlated with the Swakop Group. The formations are intensely folded by at least three episodes of which the first two are coaxial and resulted in prominent, approximately N-S trending, structures. Sn and Sn-W mineralization predominantly occurs as vein and replacement type mineralization. Vein type mineralization occurs as Brandberg West, Frans Prospect, Gamigab Prospect and the Goantagab Mining Area. The vein type mineralization is accompanied by intense alteration, consisting of greisenization, sericitization, hematitization and carbonatization. Replacement-type, hematite-cassiterite mineralization, occurs in the Goantagab Mining area in the marble close to, or at the schist marble contact. Intense ferruginous alteration of the marbles in this area, is associated with veins, which terminate against, or cross cut the marble. A regional metal zonation, ranging from Sn-W mineralization with minor sulphides at Brandberg West to Sn-sulphide mineralization at Goantagab can be detected. This metal zonation is attributed to the distance of the mineral locality from the source area, with Goantagab representing a distal and Brandberg West a proximal position relative to the source area. Structural, mineralogical and geological features of the mineralization in this area suggest that processes of ore genesis may be related to anorogenic magmatism of Karoo age.
- Full Text:
- Date Issued: 1986
- Authors: Petzel, V
- Date: 1986
- Subjects: Geology, Structural -- Namibia -- Damara Mobile Belt , Geology, Structural -- Namibia -- Kaoko Belt , Veins (Geology) -- Namibia -- Damara Mobile Belt , Veins (Geology) -- Namibia -- Kaoko Belt , Mineralogy -- Namibia -- Damara Mobile Belt , Mineralogy -- Namibia -- Kaoko Belt , Geodynamics -- Namibia -- Damara Mobile Belt , Geodynamics -- Namibia -- Kaoko Belt
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5041 , http://hdl.handle.net/10962/d1007633
- Description: The ENE trending Brandberg West - Goantagab Sn-W belt is located in the Southern Kaoko Zone of the northern coastal branch of the Damara Orogen. The lithologies in this area are turbiditic and consist of three schist units separated by two marble horizons, all of which are correlated with the Swakop Group. The formations are intensely folded by at least three episodes of which the first two are coaxial and resulted in prominent, approximately N-S trending, structures. Sn and Sn-W mineralization predominantly occurs as vein and replacement type mineralization. Vein type mineralization occurs as Brandberg West, Frans Prospect, Gamigab Prospect and the Goantagab Mining Area. The vein type mineralization is accompanied by intense alteration, consisting of greisenization, sericitization, hematitization and carbonatization. Replacement-type, hematite-cassiterite mineralization, occurs in the Goantagab Mining area in the marble close to, or at the schist marble contact. Intense ferruginous alteration of the marbles in this area, is associated with veins, which terminate against, or cross cut the marble. A regional metal zonation, ranging from Sn-W mineralization with minor sulphides at Brandberg West to Sn-sulphide mineralization at Goantagab can be detected. This metal zonation is attributed to the distance of the mineral locality from the source area, with Goantagab representing a distal and Brandberg West a proximal position relative to the source area. Structural, mineralogical and geological features of the mineralization in this area suggest that processes of ore genesis may be related to anorogenic magmatism of Karoo age.
- Full Text:
- Date Issued: 1986
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