Cobalt enrichment at the Juomasuo and Hangaslampi polymetallic deposits, Kuusamo Schist Belt, Finland: a role for an orogenic gold fluid?

W. K. Witt, S. G. Hagemann, M. Roberts, A. Davies

Research output: Contribution to journalLetter

Abstract

The Juomasuo (Co-Au) and Hangaslampi (Au-Co) deposits are located in the Kuusamo Schist Belt, part of the 1.9–1.8 Ga Svecokarelian Orogenic Belt, central Finland. The deposits are hosted by metasedimentary and mafic rocks, and structurally controlled by the F2 Kayla-Konttiaho Antiform. Hydrothermal alteration is spatially zoned, from early albite through biotite and then chlorite and late muscovite alteration. Pipe-like chlorite-quartz-pyrrhotite bodies plunge parallel to the F2 fold axis and are cut by tabular quartz-muscovite-pyrite gold lodes in the S2 axial plane orientation. The chlorite alteration zone contains 10–40 vol.% pyrrhotite containing approximately 0.25 wt% Co but whole-rock Co grades are enhanced by the late-stage and heterogeneous enrichment of minor pyrite (up to 3% Co) and introduction of cobaltian pyrite and cobalt pentlandite. Cobaltite formed where muscovite replaces chlorite within metres of the gold lodes. Cobaltite and Co-enriched pyrite formed because Co and S were mobilized from pyrrhotite in relatively S-poor gold lodes by an As-rich gold ore fluid, during late-D2. Potassium, cobalt, sulfur and arsenic were transported into the mainly chlorite-rich wallrocks, via veinlets and fractures, by the now depleted gold ore fluid. Approximately 5 vol.% pyrite in the gold lodes displays extremely variable cobalt contents, which is interpreted to reflect mobility of Co during formation of the gold lodes. The origin of the gold ore fluid is enigmatic but is most plausibly an orogenic gold fluid, despite the paucity of carbonate minerals in the gold lodes.

Original languageEnglish
JournalMineralium Deposita
DOIs
Publication statusPublished - 18 Dec 2019

Fingerprint

Finland
schist
Cobalt
cobalt
Gold
Deposits
gold
deposits
Fluids
fluid
fluids
pyrites
chlorite
pyrite
pyrrhotite
muscovite
cobaltite
minerals
Ores
Quartz

Cite this

@article{73cd8501f47349f5bfd19d470090d23a,
title = "Cobalt enrichment at the Juomasuo and Hangaslampi polymetallic deposits, Kuusamo Schist Belt, Finland: a role for an orogenic gold fluid?",
abstract = "The Juomasuo (Co-Au) and Hangaslampi (Au-Co) deposits are located in the Kuusamo Schist Belt, part of the 1.9–1.8 Ga Svecokarelian Orogenic Belt, central Finland. The deposits are hosted by metasedimentary and mafic rocks, and structurally controlled by the F2 Kayla-Konttiaho Antiform. Hydrothermal alteration is spatially zoned, from early albite through biotite and then chlorite and late muscovite alteration. Pipe-like chlorite-quartz-pyrrhotite bodies plunge parallel to the F2 fold axis and are cut by tabular quartz-muscovite-pyrite gold lodes in the S2 axial plane orientation. The chlorite alteration zone contains 10–40 vol.{\%} pyrrhotite containing approximately 0.25 wt{\%} Co but whole-rock Co grades are enhanced by the late-stage and heterogeneous enrichment of minor pyrite (up to 3{\%} Co) and introduction of cobaltian pyrite and cobalt pentlandite. Cobaltite formed where muscovite replaces chlorite within metres of the gold lodes. Cobaltite and Co-enriched pyrite formed because Co and S were mobilized from pyrrhotite in relatively S-poor gold lodes by an As-rich gold ore fluid, during late-D2. Potassium, cobalt, sulfur and arsenic were transported into the mainly chlorite-rich wallrocks, via veinlets and fractures, by the now depleted gold ore fluid. Approximately 5 vol.{\%} pyrite in the gold lodes displays extremely variable cobalt contents, which is interpreted to reflect mobility of Co during formation of the gold lodes. The origin of the gold ore fluid is enigmatic but is most plausibly an orogenic gold fluid, despite the paucity of carbonate minerals in the gold lodes.",
keywords = "Cobalt, Gold deposit, Kuusamo Schist Belt, Orogenic gold",
author = "Witt, {W. K.} and Hagemann, {S. G.} and M. Roberts and A. Davies",
year = "2019",
month = "12",
day = "18",
doi = "10.1007/s00126-019-00943-y",
language = "English",
journal = "Mineralium Deposita: international journal of geology, mineralogy, and geochemistry of mineral deposits",
issn = "0026-4598",
publisher = "Springer-Verlag London Ltd.",

}

TY - JOUR

T1 - Cobalt enrichment at the Juomasuo and Hangaslampi polymetallic deposits, Kuusamo Schist Belt, Finland

T2 - a role for an orogenic gold fluid?

AU - Witt, W. K.

AU - Hagemann, S. G.

AU - Roberts, M.

AU - Davies, A.

PY - 2019/12/18

Y1 - 2019/12/18

N2 - The Juomasuo (Co-Au) and Hangaslampi (Au-Co) deposits are located in the Kuusamo Schist Belt, part of the 1.9–1.8 Ga Svecokarelian Orogenic Belt, central Finland. The deposits are hosted by metasedimentary and mafic rocks, and structurally controlled by the F2 Kayla-Konttiaho Antiform. Hydrothermal alteration is spatially zoned, from early albite through biotite and then chlorite and late muscovite alteration. Pipe-like chlorite-quartz-pyrrhotite bodies plunge parallel to the F2 fold axis and are cut by tabular quartz-muscovite-pyrite gold lodes in the S2 axial plane orientation. The chlorite alteration zone contains 10–40 vol.% pyrrhotite containing approximately 0.25 wt% Co but whole-rock Co grades are enhanced by the late-stage and heterogeneous enrichment of minor pyrite (up to 3% Co) and introduction of cobaltian pyrite and cobalt pentlandite. Cobaltite formed where muscovite replaces chlorite within metres of the gold lodes. Cobaltite and Co-enriched pyrite formed because Co and S were mobilized from pyrrhotite in relatively S-poor gold lodes by an As-rich gold ore fluid, during late-D2. Potassium, cobalt, sulfur and arsenic were transported into the mainly chlorite-rich wallrocks, via veinlets and fractures, by the now depleted gold ore fluid. Approximately 5 vol.% pyrite in the gold lodes displays extremely variable cobalt contents, which is interpreted to reflect mobility of Co during formation of the gold lodes. The origin of the gold ore fluid is enigmatic but is most plausibly an orogenic gold fluid, despite the paucity of carbonate minerals in the gold lodes.

AB - The Juomasuo (Co-Au) and Hangaslampi (Au-Co) deposits are located in the Kuusamo Schist Belt, part of the 1.9–1.8 Ga Svecokarelian Orogenic Belt, central Finland. The deposits are hosted by metasedimentary and mafic rocks, and structurally controlled by the F2 Kayla-Konttiaho Antiform. Hydrothermal alteration is spatially zoned, from early albite through biotite and then chlorite and late muscovite alteration. Pipe-like chlorite-quartz-pyrrhotite bodies plunge parallel to the F2 fold axis and are cut by tabular quartz-muscovite-pyrite gold lodes in the S2 axial plane orientation. The chlorite alteration zone contains 10–40 vol.% pyrrhotite containing approximately 0.25 wt% Co but whole-rock Co grades are enhanced by the late-stage and heterogeneous enrichment of minor pyrite (up to 3% Co) and introduction of cobaltian pyrite and cobalt pentlandite. Cobaltite formed where muscovite replaces chlorite within metres of the gold lodes. Cobaltite and Co-enriched pyrite formed because Co and S were mobilized from pyrrhotite in relatively S-poor gold lodes by an As-rich gold ore fluid, during late-D2. Potassium, cobalt, sulfur and arsenic were transported into the mainly chlorite-rich wallrocks, via veinlets and fractures, by the now depleted gold ore fluid. Approximately 5 vol.% pyrite in the gold lodes displays extremely variable cobalt contents, which is interpreted to reflect mobility of Co during formation of the gold lodes. The origin of the gold ore fluid is enigmatic but is most plausibly an orogenic gold fluid, despite the paucity of carbonate minerals in the gold lodes.

KW - Cobalt

KW - Gold deposit

KW - Kuusamo Schist Belt

KW - Orogenic gold

UR - http://www.scopus.com/inward/record.url?scp=85076912744&partnerID=8YFLogxK

U2 - 10.1007/s00126-019-00943-y

DO - 10.1007/s00126-019-00943-y

M3 - Letter

JO - Mineralium Deposita: international journal of geology, mineralogy, and geochemistry of mineral deposits

JF - Mineralium Deposita: international journal of geology, mineralogy, and geochemistry of mineral deposits

SN - 0026-4598

ER -