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Near-infrared equipment for high-precision microthermometry measurements using the infrared microscopy technique

English title Near-infrared equipment for high-precision microthermometry measurements using the infrared microscopy technique
Applicant Moritz Robert
Number 133781
Funding scheme R'EQUIP
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Other disciplines of Earth Sciences
Start/End 01.12.2010 - 30.11.2011
Approved amount 51'800.00
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All Disciplines (2)

Discipline
Other disciplines of Earth Sciences
Geochemistry

Keywords (6)

Fluid inclusions; Microthermometry; Infra-red light microscopy; Opaque minerals; Ore deposits; near-infrared microthermometry

Lay Summary (English)

Lead
Lay summary
Fluid inclusion salinities and homogenization temperatures obtained by microthermometry of fluid inclusions trapped in minerals are fundamental pieces of information providing constraints about the source and the pathways of fluids, and about different processes occurring during the evolution of crustal fluids, such as boiling and fluid-mixing. Accurate microthermometric fluid inclusion data are a prerequisite for such interpretations and for modelling fluid processes and evolution in the Earth's crust.Metallic ore minerals are commonly opaque to visible light. Therefore, most fluid inclusion studies in ore deposits are typically restricted to the study of transparent gangue minerals, such as quartz and calcite. This assumes that ore and gangue minerals were deposited concurrently from the same fluid, under the same physico-chemical conditions. Justification for this assumption is often based on the close spatial association of the gangue and ore minerals or textural evidence that they are cogenetic. However, textural evidence for contemporaneous deposition of ore and gangue minerals is often ambiguous and misleading. Therefore, infrared fluid inclusion microthermometry has been used in recent years to collect directly data from fluid inclusions trapped in opaque minerals.However, recent studies have shown that during infrared microthermometry of opaque minerals, temperature of phase changes were a function of infrared light source intensity. It was demonstrated that high infrared light source intensity, necessary for optimum visual control during microthermometric data acquisition, resulted in dramatic overestimates of fluid inclusion salinities.The objective of the project of this grant application is to implement a technique of time-integrated, controlled reduction of infrared light intensity interacting with the analysed samples, using a Universal fast shutter developed recently, to eliminate or significantly reduce the light intensity effect (infrared heating) on salinity acquisition by microthermometry, and on homogenization temperature measurements of fluid inclusions trapped in opaque minerals, but at the same time keep a sufficient high-quality, bright image follow the phase transitions in the inclusions.Our ultimate goal is to develop and provide a technique, which will allow the Geoscience community to obtain routine, systematic microthermometric fluid inclusion data from opaque minerals with a high degree a confidence, which are necessary for high quality ore deposit modelling and fulfilling the prerequisite for accurate quantification of LA-ICP-MS analyses of fluid inclusions.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
22nd V.M.Goldschmidt Conference 2012 12.12.2011 Montreal, Canada
Swiss Geoscience Meeting 2011 11.11.2011 Zurich


Associated projects

Number Title Start Funding scheme
128324 Metallogeny of the Lesser Caucasus (Georgia, Armenia and Azerbaijan) 01.12.2009 SCOPES
51596 R'EQUIP: Acquisition of an Infrared Microscope System for Fluid Inclusion in "Opaque" Minerals 01.10.1997 R'EQUIP
108026 Fluids and Ore-forming processes in the continental Crust 01.04.2005 Project funding
138130 Episodic Mesozoic to Tertiary ore-forming events along the Lesser Caucasus and adjoining tectonic provinces 01.11.2011 Project funding
113510 Diversity of gold deposits in the Tethyan belt of southeastern Europe: markers of discrete tectonic and/or magmatic events 01.10.2006 Project funding
121510 Contrasting Cretaceous-Tertiary gold and copper ore formation along the Tethyan arc (Serbia-Bulgaria-Greece-Georgia-Armenia) 01.11.2008 Project funding
101853 Diversity of gold deposits in the Tethyan belt of southeastern Europe: markers of discrete tectonic and/or magmatic events 01.10.2003 Project funding
125258 Fluids and ore forming processes in the continental crust (cont) 01.04.2009 Project funding
116614 Fluids and Ore-forming processes in the continental Crust (cont) 01.04.2007 Project funding
155928 Episodic Mesozoic to Tertiary ore-forming events in successive geodynamic settings in an accretionary orogenic belt: the case of the Tethys orogenic belt 01.11.2014 Project funding
147076 Chemistry and P-T of fluids trapped in co-genetic opaque ore and transparent gangue minerals: What are the real ore-precipitating fluids? 01.04.2013 Project funding

Abstract

Fluid inclusion salinities and homogenization temperatures obtained by microthermometry of fluid inclusions trapped in minerals are fundamental pieces of information providing constraints about the source and the pathways of fluids, and about different processes occurring during the evolution of crustal fluids, such as boiling and fluid-mixing. Accurate microthermometric fluid inclusion data are a prerequisite for such interpretations and for modelling fluid processes and evolution in the Earth’s crust.Metallic ore minerals are commonly opaque to visible light. Therefore, most fluid inclusion studies in ore deposits are typically restricted to the study of transparent gangue minerals, such as quartz and calcite. This assumes that ore and gangue minerals were deposited concurrently from the same fluid, under the same physico-chemical conditions. Justification for this assumption is often based on the close spatial association of the gangue and ore minerals or textural evidence that they are cogenetic. However, textural evidence for contemporaneous deposition of ore and gangue minerals is often ambiguous and misleading. Therefore, infrared fluid inclusion microthermometry has been used in recent years to collect directly data from fluid inclusions trapped in opaque minerals.However, recent studies have shown that during infrared microthermometry of opaque minerals, temperature of phase changes were a function of infrared light source intensity. It was demonstrated that high infrared light source intensity, necessary for optimum visual control during microthermometric data acquisition, resulted in dramatic overestimates of fluid inclusion salinities.The objective of the project of this grant application is to implement a technique of time-integrated, controlled reduction of infrared light intensity interacting with the analysed samples, using a Universal fast shutter developed recently, to eliminate or significantly reduce the light intensity effect (infrared heating) on salinity acquisition by microthermometry, and on homogenization temperature measurements of fluid inclusions trapped in opaque minerals, but at the same time keep a sufficient high-quality, bright image follow the phase transitions in the inclusions.Our ultimate goal is to develop and provide a technique, which will allow the Geoscience community to obtain routine, systematic microthermometric fluid inclusion data from opaque minerals with a high degree a confidence, which are necessary for high quality ore deposit modelling and fulfilling the prerequisite for accurate quantification of LA-ICP-MS analyses of fluid inclusions.
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