Enigmatic alluvial sapphires from the Orosmayo Region, Jujuy Province, Northwest Argentina: Insights into their origin from in situ oxygen isotopes

Ian T. Graham, Stephen J. Harris, Laure Martin, Angela Lay, Eduardo Zappettini

Research output: Contribution to journalArticle

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Abstract

This study sought to investigate in situ oxygen isotopes (δ18O) within alluvial colorless-white to blue sapphires from the Orosmayo region, Jujuy Province, NW Argentina, in order to provide additional constraints on their origin and most likely primary geological environment. Analyses were conducted using the in situ SIMS oxygen isotope technique on the same grains that were analyzed for their mineral inclusions and major and trace element geochemistry using EMPA and LA-ICP-MS methods in our previous study. Results show a significant range in δ18O across the suite, from +4.1% to +11.2%. Additionally, akin to their trace element chemistry, there is significant variation in δ18O within individual grains, reaching a maximum of 1.6%. Both the previous analyses and δ18O results from this study suggest that these sapphires crystallized within the lower crust regime, involving a complex interplay of mantle-derived lamprophyres and carbonatites with crustal felsic rocks and both mantle- and crustal-derived metasomatic fluids. This study reinforces the importance of the in situ analysis of gem corundums, due to potential significant variation in major and trace element chemistry and ratios and even oxygen isotope ratios within discrete zones in individual grains.

Original languageEnglish
Article number390
JournalMinerals
Volume9
Issue number7
DOIs
Publication statusPublished - 27 Jun 2019

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sapphire
Trace elements
Sapphire
Isotopes
oxygen isotope
trace element
Oxygen
Gems
mantle
oxygen isotope ratio
Geochemistry
felsic rock
Secondary ion mass spectrometry
lower crust
Minerals
geochemistry
Rocks
Fluids
fluid
mineral

Cite this

@article{f2e880f66c5543a781c8197ab136ad17,
title = "Enigmatic alluvial sapphires from the Orosmayo Region, Jujuy Province, Northwest Argentina: Insights into their origin from in situ oxygen isotopes",
abstract = "This study sought to investigate in situ oxygen isotopes (δ18O) within alluvial colorless-white to blue sapphires from the Orosmayo region, Jujuy Province, NW Argentina, in order to provide additional constraints on their origin and most likely primary geological environment. Analyses were conducted using the in situ SIMS oxygen isotope technique on the same grains that were analyzed for their mineral inclusions and major and trace element geochemistry using EMPA and LA-ICP-MS methods in our previous study. Results show a significant range in δ18O across the suite, from +4.1{\%} to +11.2{\%}. Additionally, akin to their trace element chemistry, there is significant variation in δ18O within individual grains, reaching a maximum of 1.6{\%}. Both the previous analyses and δ18O results from this study suggest that these sapphires crystallized within the lower crust regime, involving a complex interplay of mantle-derived lamprophyres and carbonatites with crustal felsic rocks and both mantle- and crustal-derived metasomatic fluids. This study reinforces the importance of the in situ analysis of gem corundums, due to potential significant variation in major and trace element chemistry and ratios and even oxygen isotope ratios within discrete zones in individual grains.",
keywords = "Carbonatite, Corundum, In situ oxygen isotopes, Lamprophyre, Orosmayo argentina, Sapphires, Secondary ion mass spectrometry (SIMS)",
author = "Graham, {Ian T.} and Harris, {Stephen J.} and Laure Martin and Angela Lay and Eduardo Zappettini",
year = "2019",
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journal = "Minerals",
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Enigmatic alluvial sapphires from the Orosmayo Region, Jujuy Province, Northwest Argentina : Insights into their origin from in situ oxygen isotopes. / Graham, Ian T.; Harris, Stephen J.; Martin, Laure; Lay, Angela; Zappettini, Eduardo.

In: Minerals, Vol. 9, No. 7, 390, 27.06.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Enigmatic alluvial sapphires from the Orosmayo Region, Jujuy Province, Northwest Argentina

T2 - Insights into their origin from in situ oxygen isotopes

AU - Graham, Ian T.

AU - Harris, Stephen J.

AU - Martin, Laure

AU - Lay, Angela

AU - Zappettini, Eduardo

PY - 2019/6/27

Y1 - 2019/6/27

N2 - This study sought to investigate in situ oxygen isotopes (δ18O) within alluvial colorless-white to blue sapphires from the Orosmayo region, Jujuy Province, NW Argentina, in order to provide additional constraints on their origin and most likely primary geological environment. Analyses were conducted using the in situ SIMS oxygen isotope technique on the same grains that were analyzed for their mineral inclusions and major and trace element geochemistry using EMPA and LA-ICP-MS methods in our previous study. Results show a significant range in δ18O across the suite, from +4.1% to +11.2%. Additionally, akin to their trace element chemistry, there is significant variation in δ18O within individual grains, reaching a maximum of 1.6%. Both the previous analyses and δ18O results from this study suggest that these sapphires crystallized within the lower crust regime, involving a complex interplay of mantle-derived lamprophyres and carbonatites with crustal felsic rocks and both mantle- and crustal-derived metasomatic fluids. This study reinforces the importance of the in situ analysis of gem corundums, due to potential significant variation in major and trace element chemistry and ratios and even oxygen isotope ratios within discrete zones in individual grains.

AB - This study sought to investigate in situ oxygen isotopes (δ18O) within alluvial colorless-white to blue sapphires from the Orosmayo region, Jujuy Province, NW Argentina, in order to provide additional constraints on their origin and most likely primary geological environment. Analyses were conducted using the in situ SIMS oxygen isotope technique on the same grains that were analyzed for their mineral inclusions and major and trace element geochemistry using EMPA and LA-ICP-MS methods in our previous study. Results show a significant range in δ18O across the suite, from +4.1% to +11.2%. Additionally, akin to their trace element chemistry, there is significant variation in δ18O within individual grains, reaching a maximum of 1.6%. Both the previous analyses and δ18O results from this study suggest that these sapphires crystallized within the lower crust regime, involving a complex interplay of mantle-derived lamprophyres and carbonatites with crustal felsic rocks and both mantle- and crustal-derived metasomatic fluids. This study reinforces the importance of the in situ analysis of gem corundums, due to potential significant variation in major and trace element chemistry and ratios and even oxygen isotope ratios within discrete zones in individual grains.

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