The evolution of a Precambrian arc-related granulite facies gold deposit: Evidence from the Glenburgh deposit, Western Australia

L. K. Roche, F. J. Korhonen, S. P. Johnson, M. T D Wingate, E. A. Hancock, D. Dunkley, J. W. Zi, B. Rasmussen, J. R. Muhling, Sandra Occhipinti, M. Dunbar, J. Goldsworthy

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Gold deposits are rare in upper-amphibolite to granulite facies environments. Known examples commonly attract debate about whether they formed under these conditions or instead represent metamorphosed, metasomatic, or superimposed (retrograde) mineralization. The Glenburgh gold deposit is located in the Paleoproterozoic upper-amphibolite to granulite facies Glenburgh Terrane in the southern Gascoyne Province of Western Australia. Gold at the Glenburgh deposit is free and disseminated within quartz–biotite–garnet gneiss, amphibolite, and (post-gold) quartz–chlorite veins. No clear association with a specific host lithology has been identified and mineralization does not have a visually distinct proximal alteration assemblage. The rocks hosting the deposit represent a distinct sedimentary package that was deposited, mineralized, buried, and metamorphosed, all during arc magmatism. Features within the internal structure of gold grains, such as high-purity gold veinlets, incoherent twinning, and low silver content, suggest the gold has been through post-depositional processes such as metamorphism and deformation. Abundant sulfide minerals are interpreted to have formed by sulfidation of the host rock contemporaneously with gold mineralization, and the presence of rounded sulfide inclusions within garnet porphyroblasts illustrates the presence of a sulfide phase prior to peak metamorphism. Geochronology of zircon and monazite constrains the timing of mineralization to be younger than c. 2035 Ma—the maximum depositional age of the metasedimentary host rocks—but older than c. 1991 Ma—the peak of M1 metamorphism during the Glenburgh Orogeny; these events were synchronous with arc magmatism. Rocks at the Glenburgh deposit were likely deposited in a fore-arc or accretionary wedge, a favourable setting for porphyry Cu–Mo–Au, epithermal Au, polymetallic (Sn, W) skarn, and orogenic Au mineralization. Phase equilibria modelling of a pelitic migmatite constrains peak P–T conditions to be 865–885 °C, 6.8–7.6 kbar, consistent with elevated thermal gradients within the arc, followed by conductive cooling of arc magmas. Partial melting during peak M1 metamorphism possible caused gold remobilization. The lack of an alteration assemblage further suggests that the alteration assemblage and mineralization were recrystallized during deformation and metamorphism. However, increases in Ca and K abundance and magnetic susceptibility decreases toward mineralization, suggesting that they may constitute ore vectors.

Original languageEnglish
Pages (from-to)63-85
Number of pages23
JournalPrecambrian Research
Volume290
DOIs
Publication statusPublished - 1 Mar 2017

Fingerprint

Gold deposits
granulite facies
Gold
Precambrian
gold
mineralization
metamorphism
amphibolite
Rocks
Sulfides
sulfide
Geochronology
magmatism
Sulfide minerals
Lithology
Twinning
Garnets
Magnetic susceptibility
Silver
Phase equilibria

Cite this

Roche, L. K. ; Korhonen, F. J. ; Johnson, S. P. ; Wingate, M. T D ; Hancock, E. A. ; Dunkley, D. ; Zi, J. W. ; Rasmussen, B. ; Muhling, J. R. ; Occhipinti, Sandra ; Dunbar, M. ; Goldsworthy, J. / The evolution of a Precambrian arc-related granulite facies gold deposit : Evidence from the Glenburgh deposit, Western Australia. In: Precambrian Research. 2017 ; Vol. 290. pp. 63-85.
@article{12de0801a95e40c6b4d057d781524d09,
title = "The evolution of a Precambrian arc-related granulite facies gold deposit: Evidence from the Glenburgh deposit, Western Australia",
abstract = "Gold deposits are rare in upper-amphibolite to granulite facies environments. Known examples commonly attract debate about whether they formed under these conditions or instead represent metamorphosed, metasomatic, or superimposed (retrograde) mineralization. The Glenburgh gold deposit is located in the Paleoproterozoic upper-amphibolite to granulite facies Glenburgh Terrane in the southern Gascoyne Province of Western Australia. Gold at the Glenburgh deposit is free and disseminated within quartz–biotite–garnet gneiss, amphibolite, and (post-gold) quartz–chlorite veins. No clear association with a specific host lithology has been identified and mineralization does not have a visually distinct proximal alteration assemblage. The rocks hosting the deposit represent a distinct sedimentary package that was deposited, mineralized, buried, and metamorphosed, all during arc magmatism. Features within the internal structure of gold grains, such as high-purity gold veinlets, incoherent twinning, and low silver content, suggest the gold has been through post-depositional processes such as metamorphism and deformation. Abundant sulfide minerals are interpreted to have formed by sulfidation of the host rock contemporaneously with gold mineralization, and the presence of rounded sulfide inclusions within garnet porphyroblasts illustrates the presence of a sulfide phase prior to peak metamorphism. Geochronology of zircon and monazite constrains the timing of mineralization to be younger than c. 2035 Ma—the maximum depositional age of the metasedimentary host rocks—but older than c. 1991 Ma—the peak of M1 metamorphism during the Glenburgh Orogeny; these events were synchronous with arc magmatism. Rocks at the Glenburgh deposit were likely deposited in a fore-arc or accretionary wedge, a favourable setting for porphyry Cu–Mo–Au, epithermal Au, polymetallic (Sn, W) skarn, and orogenic Au mineralization. Phase equilibria modelling of a pelitic migmatite constrains peak P–T conditions to be 865–885 °C, 6.8–7.6 kbar, consistent with elevated thermal gradients within the arc, followed by conductive cooling of arc magmas. Partial melting during peak M1 metamorphism possible caused gold remobilization. The lack of an alteration assemblage further suggests that the alteration assemblage and mineralization were recrystallized during deformation and metamorphism. However, increases in Ca and K abundance and magnetic susceptibility decreases toward mineralization, suggesting that they may constitute ore vectors.",
author = "Roche, {L. K.} and Korhonen, {F. J.} and Johnson, {S. P.} and Wingate, {M. T D} and Hancock, {E. A.} and D. Dunkley and Zi, {J. W.} and B. Rasmussen and Muhling, {J. R.} and Sandra Occhipinti and M. Dunbar and J. Goldsworthy",
year = "2017",
month = "3",
day = "1",
doi = "10.1016/j.precamres.2016.12.007",
language = "English",
volume = "290",
pages = "63--85",
journal = "Precambrian Research",
issn = "0301-9268",
publisher = "Pergamon",

}

The evolution of a Precambrian arc-related granulite facies gold deposit : Evidence from the Glenburgh deposit, Western Australia. / Roche, L. K.; Korhonen, F. J.; Johnson, S. P.; Wingate, M. T D; Hancock, E. A.; Dunkley, D.; Zi, J. W.; Rasmussen, B.; Muhling, J. R.; Occhipinti, Sandra; Dunbar, M.; Goldsworthy, J.

In: Precambrian Research, Vol. 290, 01.03.2017, p. 63-85.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The evolution of a Precambrian arc-related granulite facies gold deposit

T2 - Evidence from the Glenburgh deposit, Western Australia

AU - Roche, L. K.

AU - Korhonen, F. J.

AU - Johnson, S. P.

AU - Wingate, M. T D

AU - Hancock, E. A.

AU - Dunkley, D.

AU - Zi, J. W.

AU - Rasmussen, B.

AU - Muhling, J. R.

AU - Occhipinti, Sandra

AU - Dunbar, M.

AU - Goldsworthy, J.

PY - 2017/3/1

Y1 - 2017/3/1

N2 - Gold deposits are rare in upper-amphibolite to granulite facies environments. Known examples commonly attract debate about whether they formed under these conditions or instead represent metamorphosed, metasomatic, or superimposed (retrograde) mineralization. The Glenburgh gold deposit is located in the Paleoproterozoic upper-amphibolite to granulite facies Glenburgh Terrane in the southern Gascoyne Province of Western Australia. Gold at the Glenburgh deposit is free and disseminated within quartz–biotite–garnet gneiss, amphibolite, and (post-gold) quartz–chlorite veins. No clear association with a specific host lithology has been identified and mineralization does not have a visually distinct proximal alteration assemblage. The rocks hosting the deposit represent a distinct sedimentary package that was deposited, mineralized, buried, and metamorphosed, all during arc magmatism. Features within the internal structure of gold grains, such as high-purity gold veinlets, incoherent twinning, and low silver content, suggest the gold has been through post-depositional processes such as metamorphism and deformation. Abundant sulfide minerals are interpreted to have formed by sulfidation of the host rock contemporaneously with gold mineralization, and the presence of rounded sulfide inclusions within garnet porphyroblasts illustrates the presence of a sulfide phase prior to peak metamorphism. Geochronology of zircon and monazite constrains the timing of mineralization to be younger than c. 2035 Ma—the maximum depositional age of the metasedimentary host rocks—but older than c. 1991 Ma—the peak of M1 metamorphism during the Glenburgh Orogeny; these events were synchronous with arc magmatism. Rocks at the Glenburgh deposit were likely deposited in a fore-arc or accretionary wedge, a favourable setting for porphyry Cu–Mo–Au, epithermal Au, polymetallic (Sn, W) skarn, and orogenic Au mineralization. Phase equilibria modelling of a pelitic migmatite constrains peak P–T conditions to be 865–885 °C, 6.8–7.6 kbar, consistent with elevated thermal gradients within the arc, followed by conductive cooling of arc magmas. Partial melting during peak M1 metamorphism possible caused gold remobilization. The lack of an alteration assemblage further suggests that the alteration assemblage and mineralization were recrystallized during deformation and metamorphism. However, increases in Ca and K abundance and magnetic susceptibility decreases toward mineralization, suggesting that they may constitute ore vectors.

AB - Gold deposits are rare in upper-amphibolite to granulite facies environments. Known examples commonly attract debate about whether they formed under these conditions or instead represent metamorphosed, metasomatic, or superimposed (retrograde) mineralization. The Glenburgh gold deposit is located in the Paleoproterozoic upper-amphibolite to granulite facies Glenburgh Terrane in the southern Gascoyne Province of Western Australia. Gold at the Glenburgh deposit is free and disseminated within quartz–biotite–garnet gneiss, amphibolite, and (post-gold) quartz–chlorite veins. No clear association with a specific host lithology has been identified and mineralization does not have a visually distinct proximal alteration assemblage. The rocks hosting the deposit represent a distinct sedimentary package that was deposited, mineralized, buried, and metamorphosed, all during arc magmatism. Features within the internal structure of gold grains, such as high-purity gold veinlets, incoherent twinning, and low silver content, suggest the gold has been through post-depositional processes such as metamorphism and deformation. Abundant sulfide minerals are interpreted to have formed by sulfidation of the host rock contemporaneously with gold mineralization, and the presence of rounded sulfide inclusions within garnet porphyroblasts illustrates the presence of a sulfide phase prior to peak metamorphism. Geochronology of zircon and monazite constrains the timing of mineralization to be younger than c. 2035 Ma—the maximum depositional age of the metasedimentary host rocks—but older than c. 1991 Ma—the peak of M1 metamorphism during the Glenburgh Orogeny; these events were synchronous with arc magmatism. Rocks at the Glenburgh deposit were likely deposited in a fore-arc or accretionary wedge, a favourable setting for porphyry Cu–Mo–Au, epithermal Au, polymetallic (Sn, W) skarn, and orogenic Au mineralization. Phase equilibria modelling of a pelitic migmatite constrains peak P–T conditions to be 865–885 °C, 6.8–7.6 kbar, consistent with elevated thermal gradients within the arc, followed by conductive cooling of arc magmas. Partial melting during peak M1 metamorphism possible caused gold remobilization. The lack of an alteration assemblage further suggests that the alteration assemblage and mineralization were recrystallized during deformation and metamorphism. However, increases in Ca and K abundance and magnetic susceptibility decreases toward mineralization, suggesting that they may constitute ore vectors.

UR - http://www.scopus.com/inward/record.url?scp=85009126442&partnerID=8YFLogxK

U2 - 10.1016/j.precamres.2016.12.007

DO - 10.1016/j.precamres.2016.12.007

M3 - Article

VL - 290

SP - 63

EP - 85

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

ER -