The factors affecting the interpretation of geochemical surveys in mineral exploration
- Authors: Fletcher, B A
- Date: 1982
- Subjects: Geochemistry , Geochemistry -- Environmental aspects , Mining geology , Minerals , Ore deposits , Geochemical prospecting
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5014 , http://hdl.handle.net/10962/d1006142
- Description: [From introduction] Exploration geochemistry is an indirect method of detecting mineral deposits by measuring the abundance and distribution of ore elements and elements closely associated with ore in natural materials at or near the earth's surface. The method relies on the assumption that a mineral deposit is reflected by unusual element abundances or distribution patterns (geochemical halos), and that these indications of mineralization can be detected by geochemical surveys involving the collection and analysis of natural materials. The interpretation of geochemical surveys in mineral exploration involves: 1) The use of geological and statistical inference, based on a knowledge of the normal behaviour and distribution of indicator elements in the exploration area, to recognize apparent geochemical anomalies in field and analytical data and to predict the type of geochemical halo reflected by the anomalies. 11) The use of geological inference, based on a knowledge of the characteristics of geochemical halos and their relationship to mineral deposits, to predict the presence and probable location of an ore body. The interpretation process is, however, complicated by the absence of a simple universal formula that relates the abundance and distribution of elements in natural materials to the presence or absence of a mineral deposit. The interpretation of a geochemical survey must, thus, be based on an empirical approach which avaluates each survey as an individual problem. The objective of this dissertation is to illustrate the factors affecting the "nuts and bolts" approach to the interpretation of geochemical surveys in mineral exploration. The discussion is aimed at providing field geologists responsible -for the planning and execution of geochemical surveys with some basic guidelines for interpreting the surveys. I hope that the contents of this dissertation will help field geologists to "look in the last place first".
- Full Text:
- Date Issued: 1982
- Authors: Fletcher, B A
- Date: 1982
- Subjects: Geochemistry , Geochemistry -- Environmental aspects , Mining geology , Minerals , Ore deposits , Geochemical prospecting
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5014 , http://hdl.handle.net/10962/d1006142
- Description: [From introduction] Exploration geochemistry is an indirect method of detecting mineral deposits by measuring the abundance and distribution of ore elements and elements closely associated with ore in natural materials at or near the earth's surface. The method relies on the assumption that a mineral deposit is reflected by unusual element abundances or distribution patterns (geochemical halos), and that these indications of mineralization can be detected by geochemical surveys involving the collection and analysis of natural materials. The interpretation of geochemical surveys in mineral exploration involves: 1) The use of geological and statistical inference, based on a knowledge of the normal behaviour and distribution of indicator elements in the exploration area, to recognize apparent geochemical anomalies in field and analytical data and to predict the type of geochemical halo reflected by the anomalies. 11) The use of geological inference, based on a knowledge of the characteristics of geochemical halos and their relationship to mineral deposits, to predict the presence and probable location of an ore body. The interpretation process is, however, complicated by the absence of a simple universal formula that relates the abundance and distribution of elements in natural materials to the presence or absence of a mineral deposit. The interpretation of a geochemical survey must, thus, be based on an empirical approach which avaluates each survey as an individual problem. The objective of this dissertation is to illustrate the factors affecting the "nuts and bolts" approach to the interpretation of geochemical surveys in mineral exploration. The discussion is aimed at providing field geologists responsible -for the planning and execution of geochemical surveys with some basic guidelines for interpreting the surveys. I hope that the contents of this dissertation will help field geologists to "look in the last place first".
- Full Text:
- Date Issued: 1982
The geology, geochemistry and silicate mineralogy of the upper criticial zone of the north-western Bushveld Complex, at Rustenburg Platinum Mines, Union Section
- Authors: De Klerk, William Johan
- Date: 1982 , 2013-03-20
- Subjects: Mineralogy -- South Africa -- North-Western Transvaal , Geochemistry -- South Africa -- North-Western Transvaal , Geology -- South Africa -- North-Western Transvaal , Platinum mines and mining -- South Africa -- North-Western Transvaal , Rustenburg Platinum Mines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5013 , http://hdl.handle.net/10962/d1006140 , Mineralogy -- South Africa -- North-Western Transvaal , Geochemistry -- South Africa -- North-Western Transvaal , Geology -- South Africa -- North-Western Transvaal , Platinum mines and mining -- South Africa -- North-Western Transvaal , Rustenburg Platinum Mines
- Description: Rustenburg Platinum Mines, Union Section, is located in the mafic phase of the north-western sector of the Bushveld Complex. This part of the Complex is characterised by transgressions of Upper zone ferrogabbros across the lower sequence of mafic rocks. These transgressions have effectively isolated a roughly triangular segment of Lower, Critical and Main zone rocks. It is in the upper part of the Critical zone that the Merensky Reef, with a strike length of 9,5 km, is found to suboutcrop below a 2-3 m black turf soil cover and it constitutes the orebody being mined at Union Section. Underground mining and development have exposed a stratigraphic succession from the Middle Group chromitites to within the lower part of the Main zone gabbros. A detailed investigation of a 100 m stratigraphic succession was undertaken in the upper part of the Critical zone, which includes the Bastard Reef, Merensky Reef, Pseudo Reef, UG 2 and UG 1 layers. Stratigraphic descriptions are presented for both a normal and potholed succession, as well as a description of pothole characteristics. The variations of Merensky Reef thickness, pothole distribution and structure of the are body are also discussed. Forty seven whole-rock major- and trace-element analyses were carried out on selected samples from both normal and potholed successions, although more emphasis was placed on the former. These samples were taken from just below the UG 1 to above the Bastard Reef. Trace elements determined included Sr, Rb, Y, Nb, Zr, Cr, Co, Ni, Cu and V. The cyclical nature of the layering is clearly defined by breaks in the trends of both the major- and trace element analyses, although some elements are strongly influenced by the modal proportions of the mai n mineral phases. Although major breaks are observed for individual elements , insignificant variation of the Mg/Mg+Fe 2 + ratio is observed throughout. New electron microprobe data are presented for the main silicate phases olivine , orthopyroxene, clinopyroxene and plagioclase , while only a limi ted number of analyses were carried out on the spine l phase. There would appear to be a reversal of the expected fractionation trend from the hanging wal l of the UG 2 to the Pseudo Marker layer. There is an upward increase of the Fo content of the olivine from F0₇₆ , ₇₋₈₁,₆ . A similar trend is observed for the orthopyroxene analyses . The Merensky unit, as a whole, exhibits a gradual decrease in the Mg end member of the Ca-poor pyroxenes from En ₇₈,₅₋₇₄ . was found to be markedly more calcic Cumulus plagioclase (An ₇₂, ₈-₈₁, ₇) than the intercumulus phase (An₅₆,₃₋₇₁, ₉) ' A further feature of the cumulus plagioclase is that strong zonation was observed with the cores of individual crystals being consistently lower in Ca relative to their margins . , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1982
- Authors: De Klerk, William Johan
- Date: 1982 , 2013-03-20
- Subjects: Mineralogy -- South Africa -- North-Western Transvaal , Geochemistry -- South Africa -- North-Western Transvaal , Geology -- South Africa -- North-Western Transvaal , Platinum mines and mining -- South Africa -- North-Western Transvaal , Rustenburg Platinum Mines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5013 , http://hdl.handle.net/10962/d1006140 , Mineralogy -- South Africa -- North-Western Transvaal , Geochemistry -- South Africa -- North-Western Transvaal , Geology -- South Africa -- North-Western Transvaal , Platinum mines and mining -- South Africa -- North-Western Transvaal , Rustenburg Platinum Mines
- Description: Rustenburg Platinum Mines, Union Section, is located in the mafic phase of the north-western sector of the Bushveld Complex. This part of the Complex is characterised by transgressions of Upper zone ferrogabbros across the lower sequence of mafic rocks. These transgressions have effectively isolated a roughly triangular segment of Lower, Critical and Main zone rocks. It is in the upper part of the Critical zone that the Merensky Reef, with a strike length of 9,5 km, is found to suboutcrop below a 2-3 m black turf soil cover and it constitutes the orebody being mined at Union Section. Underground mining and development have exposed a stratigraphic succession from the Middle Group chromitites to within the lower part of the Main zone gabbros. A detailed investigation of a 100 m stratigraphic succession was undertaken in the upper part of the Critical zone, which includes the Bastard Reef, Merensky Reef, Pseudo Reef, UG 2 and UG 1 layers. Stratigraphic descriptions are presented for both a normal and potholed succession, as well as a description of pothole characteristics. The variations of Merensky Reef thickness, pothole distribution and structure of the are body are also discussed. Forty seven whole-rock major- and trace-element analyses were carried out on selected samples from both normal and potholed successions, although more emphasis was placed on the former. These samples were taken from just below the UG 1 to above the Bastard Reef. Trace elements determined included Sr, Rb, Y, Nb, Zr, Cr, Co, Ni, Cu and V. The cyclical nature of the layering is clearly defined by breaks in the trends of both the major- and trace element analyses, although some elements are strongly influenced by the modal proportions of the mai n mineral phases. Although major breaks are observed for individual elements , insignificant variation of the Mg/Mg+Fe 2 + ratio is observed throughout. New electron microprobe data are presented for the main silicate phases olivine , orthopyroxene, clinopyroxene and plagioclase , while only a limi ted number of analyses were carried out on the spine l phase. There would appear to be a reversal of the expected fractionation trend from the hanging wal l of the UG 2 to the Pseudo Marker layer. There is an upward increase of the Fo content of the olivine from F0₇₆ , ₇₋₈₁,₆ . A similar trend is observed for the orthopyroxene analyses . The Merensky unit, as a whole, exhibits a gradual decrease in the Mg end member of the Ca-poor pyroxenes from En ₇₈,₅₋₇₄ . was found to be markedly more calcic Cumulus plagioclase (An ₇₂, ₈-₈₁, ₇) than the intercumulus phase (An₅₆,₃₋₇₁, ₉) ' A further feature of the cumulus plagioclase is that strong zonation was observed with the cores of individual crystals being consistently lower in Ca relative to their margins . , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1982
The stratigraphy and structure of the Kommadagga subgroup and contiguous rocks|
- Authors: Swart, Roger
- Date: 1982
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4919 , http://hdl.handle.net/10962/d1004378
- Description: The Lake Mentz and Kommadagga Subgroups were deposited in a marine environment and are characterised by a heterogeneous sequence of sediments, which range in grain size from clays to grits. During the first phase of deposition the Kweekvlei Shale and Floriskraal Formations were deposited in a prograding shoreline environment, whereas the succeeding Waaipoort Shale Formation is interpreted as represnting a reworked shoreline . The final phase of deposition of the Cape Supergroup was a regressive one in which the Kommadagga Subgroup was formed. The coarsening upward cycle of this subgroup represents a deltaic deposit. A significant time gap appears to exist before the deposition of the glacial-marine Dwyka Tillite Formation. Structurally, the area was subjected to deformation by buckle folding at about 250 Ma into a series of folds with southward dipping axial planes. Only one phase of deformation is recognised in the study area . A decrease in pore space, mineral overgrowths,formation of silica and calcite cements and development of autigenic minerals such as opal, stilpnomelane, analcite, prehnite, muscovite and various clay minerals are the characteristic diagenetic features of the sediments. The mineralogical evidence suggests that the maximum temperature and pressure of burial was 150 C and 4 to 5 Kbar respectively.
- Full Text:
- Date Issued: 1982
- Authors: Swart, Roger
- Date: 1982
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4919 , http://hdl.handle.net/10962/d1004378
- Description: The Lake Mentz and Kommadagga Subgroups were deposited in a marine environment and are characterised by a heterogeneous sequence of sediments, which range in grain size from clays to grits. During the first phase of deposition the Kweekvlei Shale and Floriskraal Formations were deposited in a prograding shoreline environment, whereas the succeeding Waaipoort Shale Formation is interpreted as represnting a reworked shoreline . The final phase of deposition of the Cape Supergroup was a regressive one in which the Kommadagga Subgroup was formed. The coarsening upward cycle of this subgroup represents a deltaic deposit. A significant time gap appears to exist before the deposition of the glacial-marine Dwyka Tillite Formation. Structurally, the area was subjected to deformation by buckle folding at about 250 Ma into a series of folds with southward dipping axial planes. Only one phase of deformation is recognised in the study area . A decrease in pore space, mineral overgrowths,formation of silica and calcite cements and development of autigenic minerals such as opal, stilpnomelane, analcite, prehnite, muscovite and various clay minerals are the characteristic diagenetic features of the sediments. The mineralogical evidence suggests that the maximum temperature and pressure of burial was 150 C and 4 to 5 Kbar respectively.
- Full Text:
- Date Issued: 1982
The tectonic framework of magmatism and mineralization in the western United States
- Authors: Empsall, J S
- Date: 1982 , 2013-04-03
- Subjects: Plate tectonics -- United States , Magmatism -- United States , Mineralogy -- United States
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5019 , http://hdl.handle.net/10962/d1006328 , Plate tectonics -- United States , Magmatism -- United States , Mineralogy -- United States
- Description: KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1982
- Authors: Empsall, J S
- Date: 1982 , 2013-04-03
- Subjects: Plate tectonics -- United States , Magmatism -- United States , Mineralogy -- United States
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5019 , http://hdl.handle.net/10962/d1006328 , Plate tectonics -- United States , Magmatism -- United States , Mineralogy -- United States
- Description: KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1982
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