The role of ground melting in the genesis of komatiite-associated nickel sulfide deposits at Kambalda and Widgiemooltha, Western Australia

Kevin Mark Frost

Research output: ThesisDoctoral Thesis

9 Downloads (Pure)

Abstract

[Truncated] Komatiite-associated nickel sulfide deposits are the world's premier source of sulfide nickel from Archaean greenstone belts. These deposits comprise two main associations in Western Australia: i) low-grade disseminated nickel sulfide mineralization in thick komatiitic-dunite bodies, and ii) high-grade disseminated/matrix/massive nickel sulfides at the base of multiple-flow komatiite sequences. Kambalda is the type-example of the latter association, and these deposits, together with similar deposits at Widgiemooltha, are best suited for study of the genesis of their nickel sulfide ores.
The timing of sulfur saturation which resulted in the segregation of sulfide-oxide rich melts, that subsequently settled and accumulated at the base of the mineralized komatiite flows forming the nickel sulfide ores, is one of the more controversial aspects of ore genesis at Kambalda. Further controversy arises from the difficulty indiscriminating between mantle and sedimentary sources of sulfur in the sulfide ores.
Previous studies at Kambalda have emphasized the volcanic features of these deposits. The mineralized komatiite sequence is overlain and underlain by pillow basalts, and sulfidic and carbonaceous sedimentary rocks occur at regular intervals in the volcanic succession, particularly in the lowermost komatiite member, indicating a deep marine volcanic setting. The komatiites display characteristic flow-top breccias, polygonal jointing, and a wide variety of spinifex, crescumulate, and equant cumulate textures, consistent with their emplacement as lava flows. The nickel sulfide mineralization is restricted to the lowermost komatiite flows, which are the thickest and most magnesian komatiites of the entire komatiite sequence. In addition, nickel ores are confined to discrete volcanic environments which are characterized by thick, highly magnesian, cumulate-dominant flows, partially confined to highly elongate depressions in the underlying basalt sequence. The laterally-contiguous, barren, flanking-ore environments comprise several thinner, less-magnesian komatiite flows overlying relatively planar basalt substrates. Ore environments are n o w generally accepted as lava channels in which there was substantial turbulent flow of highly magnesian komatiite partly localised in primary topographic depressions (lava-channel fades). The relationships between ore environments and the barren flanking-ore environments are complex and indicate time stratigraphic discontinuities in the lava pile. The flanking-ore flows probably accumulated in lava levee areas (sheet-flow fades) by the repeated spillage of komatiite from the channel during periodic lava emplacement.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • The University of Western Australia
DOIs
Publication statusUnpublished - 1992

Fingerprint

komatiite
nickel
melting
sulfide
lava
basalt
cumulate
emplacement
sulfur
ore
mineralization
volcanic feature
sheet flow
dunite
levee
greenstone belt
turbulent flow
lava flow
sedimentary rock
Archean

Bibliographical note

This thesis has been made available in the UWA Profiles and Research Repository as part of a UWA Library project to digitise and make available theses completed before 2003. If you are the author of this thesis and would like it removed from the UWA Profiles and Research Repository, please contact digitaltheses-lib@uwa.edu.au

Cite this

@phdthesis{eb000539ccf8484792a8c394990ae87a,
title = "The role of ground melting in the genesis of komatiite-associated nickel sulfide deposits at Kambalda and Widgiemooltha, Western Australia",
abstract = "[Truncated] Komatiite-associated nickel sulfide deposits are the world's premier source of sulfide nickel from Archaean greenstone belts. These deposits comprise two main associations in Western Australia: i) low-grade disseminated nickel sulfide mineralization in thick komatiitic-dunite bodies, and ii) high-grade disseminated/matrix/massive nickel sulfides at the base of multiple-flow komatiite sequences. Kambalda is the type-example of the latter association, and these deposits, together with similar deposits at Widgiemooltha, are best suited for study of the genesis of their nickel sulfide ores. The timing of sulfur saturation which resulted in the segregation of sulfide-oxide rich melts, that subsequently settled and accumulated at the base of the mineralized komatiite flows forming the nickel sulfide ores, is one of the more controversial aspects of ore genesis at Kambalda. Further controversy arises from the difficulty indiscriminating between mantle and sedimentary sources of sulfur in the sulfide ores. Previous studies at Kambalda have emphasized the volcanic features of these deposits. The mineralized komatiite sequence is overlain and underlain by pillow basalts, and sulfidic and carbonaceous sedimentary rocks occur at regular intervals in the volcanic succession, particularly in the lowermost komatiite member, indicating a deep marine volcanic setting. The komatiites display characteristic flow-top breccias, polygonal jointing, and a wide variety of spinifex, crescumulate, and equant cumulate textures, consistent with their emplacement as lava flows. The nickel sulfide mineralization is restricted to the lowermost komatiite flows, which are the thickest and most magnesian komatiites of the entire komatiite sequence. In addition, nickel ores are confined to discrete volcanic environments which are characterized by thick, highly magnesian, cumulate-dominant flows, partially confined to highly elongate depressions in the underlying basalt sequence. The laterally-contiguous, barren, flanking-ore environments comprise several thinner, less-magnesian komatiite flows overlying relatively planar basalt substrates. Ore environments are n o w generally accepted as lava channels in which there was substantial turbulent flow of highly magnesian komatiite partly localised in primary topographic depressions (lava-channel fades). The relationships between ore environments and the barren flanking-ore environments are complex and indicate time stratigraphic discontinuities in the lava pile. The flanking-ore flows probably accumulated in lava levee areas (sheet-flow fades) by the repeated spillage of komatiite from the channel during periodic lava emplacement.",
author = "Frost, {Kevin Mark}",
note = "This thesis has been made available in the UWA Profiles and Research Repository as part of a UWA Library project to digitise and make available theses completed before 2003. If you are the author of this thesis and would like it removed from the UWA Profiles and Research Repository, please contact digitaltheses-lib@uwa.edu.au",
year = "1992",
doi = "10.26182/5c6a2075a4bc1",
language = "English",
school = "The University of Western Australia",

}

TY - THES

T1 - The role of ground melting in the genesis of komatiite-associated nickel sulfide deposits at Kambalda and Widgiemooltha, Western Australia

AU - Frost, Kevin Mark

N1 - This thesis has been made available in the UWA Profiles and Research Repository as part of a UWA Library project to digitise and make available theses completed before 2003. If you are the author of this thesis and would like it removed from the UWA Profiles and Research Repository, please contact digitaltheses-lib@uwa.edu.au

PY - 1992

Y1 - 1992

N2 - [Truncated] Komatiite-associated nickel sulfide deposits are the world's premier source of sulfide nickel from Archaean greenstone belts. These deposits comprise two main associations in Western Australia: i) low-grade disseminated nickel sulfide mineralization in thick komatiitic-dunite bodies, and ii) high-grade disseminated/matrix/massive nickel sulfides at the base of multiple-flow komatiite sequences. Kambalda is the type-example of the latter association, and these deposits, together with similar deposits at Widgiemooltha, are best suited for study of the genesis of their nickel sulfide ores. The timing of sulfur saturation which resulted in the segregation of sulfide-oxide rich melts, that subsequently settled and accumulated at the base of the mineralized komatiite flows forming the nickel sulfide ores, is one of the more controversial aspects of ore genesis at Kambalda. Further controversy arises from the difficulty indiscriminating between mantle and sedimentary sources of sulfur in the sulfide ores. Previous studies at Kambalda have emphasized the volcanic features of these deposits. The mineralized komatiite sequence is overlain and underlain by pillow basalts, and sulfidic and carbonaceous sedimentary rocks occur at regular intervals in the volcanic succession, particularly in the lowermost komatiite member, indicating a deep marine volcanic setting. The komatiites display characteristic flow-top breccias, polygonal jointing, and a wide variety of spinifex, crescumulate, and equant cumulate textures, consistent with their emplacement as lava flows. The nickel sulfide mineralization is restricted to the lowermost komatiite flows, which are the thickest and most magnesian komatiites of the entire komatiite sequence. In addition, nickel ores are confined to discrete volcanic environments which are characterized by thick, highly magnesian, cumulate-dominant flows, partially confined to highly elongate depressions in the underlying basalt sequence. The laterally-contiguous, barren, flanking-ore environments comprise several thinner, less-magnesian komatiite flows overlying relatively planar basalt substrates. Ore environments are n o w generally accepted as lava channels in which there was substantial turbulent flow of highly magnesian komatiite partly localised in primary topographic depressions (lava-channel fades). The relationships between ore environments and the barren flanking-ore environments are complex and indicate time stratigraphic discontinuities in the lava pile. The flanking-ore flows probably accumulated in lava levee areas (sheet-flow fades) by the repeated spillage of komatiite from the channel during periodic lava emplacement.

AB - [Truncated] Komatiite-associated nickel sulfide deposits are the world's premier source of sulfide nickel from Archaean greenstone belts. These deposits comprise two main associations in Western Australia: i) low-grade disseminated nickel sulfide mineralization in thick komatiitic-dunite bodies, and ii) high-grade disseminated/matrix/massive nickel sulfides at the base of multiple-flow komatiite sequences. Kambalda is the type-example of the latter association, and these deposits, together with similar deposits at Widgiemooltha, are best suited for study of the genesis of their nickel sulfide ores. The timing of sulfur saturation which resulted in the segregation of sulfide-oxide rich melts, that subsequently settled and accumulated at the base of the mineralized komatiite flows forming the nickel sulfide ores, is one of the more controversial aspects of ore genesis at Kambalda. Further controversy arises from the difficulty indiscriminating between mantle and sedimentary sources of sulfur in the sulfide ores. Previous studies at Kambalda have emphasized the volcanic features of these deposits. The mineralized komatiite sequence is overlain and underlain by pillow basalts, and sulfidic and carbonaceous sedimentary rocks occur at regular intervals in the volcanic succession, particularly in the lowermost komatiite member, indicating a deep marine volcanic setting. The komatiites display characteristic flow-top breccias, polygonal jointing, and a wide variety of spinifex, crescumulate, and equant cumulate textures, consistent with their emplacement as lava flows. The nickel sulfide mineralization is restricted to the lowermost komatiite flows, which are the thickest and most magnesian komatiites of the entire komatiite sequence. In addition, nickel ores are confined to discrete volcanic environments which are characterized by thick, highly magnesian, cumulate-dominant flows, partially confined to highly elongate depressions in the underlying basalt sequence. The laterally-contiguous, barren, flanking-ore environments comprise several thinner, less-magnesian komatiite flows overlying relatively planar basalt substrates. Ore environments are n o w generally accepted as lava channels in which there was substantial turbulent flow of highly magnesian komatiite partly localised in primary topographic depressions (lava-channel fades). The relationships between ore environments and the barren flanking-ore environments are complex and indicate time stratigraphic discontinuities in the lava pile. The flanking-ore flows probably accumulated in lava levee areas (sheet-flow fades) by the repeated spillage of komatiite from the channel during periodic lava emplacement.

U2 - 10.26182/5c6a2075a4bc1

DO - 10.26182/5c6a2075a4bc1

M3 - Doctoral Thesis

ER -