April 2020 - Volume 16, Number 2

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Raman Spectroscopy in Earth and Planetary Sciences

Jill D. Pasteris and Olivier Beyssac Guest Editors

Table of Contents

Overview

The application of Raman (microprobe) spectroscopy in the geosciences has rapidly broadened and deepened over the past 40 years. This has been sparked by both improvements in technology and recognition of the quantitative, as well as qualitative, capabilities of the technique.  Raman spectroscopy claims relative ease of use; is typically nondestructive at the (sub-)micrometer scale; has the ability to analyze solids, liquids, and gases; can differentiate polymorphs; and can enlarge the available spectral databases for minerals especially.  Petrologists, geologists, mineralogists, geochemists, and geobiologists can create Raman maps/images based on selected spectral features, which simultaneously capture chemical–structural and microtextural information.  In a single sample, one may investigate quantitatively the PT path history during metamorphism, determine the composition and internal pressure of mixed volatiles in micrometer-size fluid inclusions, study the strain pattern or radiation damage in minerals, and/or target possible biosignatures.

  • Welcome to Raman Spectroscopy: Successes, Challenges, and Pitfalls 
  • Microscale Chemistry: Raman Analysis of Fluid and Melt Inclusions
  • Applications of Raman Spectroscopy in Mineralogy and Geochemistry 
  • Applications of Raman Spectroscopy in Metamorphic Petrology and Tectonics 
  • Geoscience Meets Biology: Raman Spectroscopy in Geobiology and Biomineralization
  • New Trends in Raman Spectroscopy: From High-Resolution Geochemistry to Planetary Exploration
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2020 Topics

Thematic Articles

Welcome to Raman Spectroscopy: Successes, Challenges, and Pitfalls

By and

Geoscientists quickly recognized the broad applicability of Raman microprobe spectroscopy to the Earth and planetary sciences, especially after commercially built microprobe instruments became available in the early 1980s. Raman spectra are sensitive to even minor (chemical or structural) perturbations within chemical bonds in (even amorphous) solids, liquids, and gases and can, thus, help identify, characterize, and differentiate between individual minerals, fluid inclusions, glasses, carbonaceous materials, solid solution phases, strain in minerals, and dissolved species in multi-component solutions. The articles in this issue explore how Raman spectroscopy has deepened and broadened our understanding of geological and extraterrestrial materials and processes.

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Microscale Chemistry: Raman Analysis of Fluid and Melt Inclusions

By and

Raman spectroscopy is a commonly applied nondestructive analytical technique for characterizing fluid and melt inclusions. The exceptional spatial resolution (~1 µm) and excellent spectral resolution (≤1 cm−1) permits the characterization of micrometer-scale phases and allows quantitative analyses based on Raman spectral features. Data provided by Raman analysis of fluid and melt inclusions has significantly advanced our understanding of complex geologic processes, including preeruptive volatile contents of magmas, the nature of fluids in the deep crust and upper mantle, the generation and evolution of methane-bearing fluids in unconventional hydrocarbon reservoirs. Anticipated future advances include the development of Raman mass spectroscopy and the use of Raman to monitor reaction progress in synthetic and natural fluid inclusion microreactors.

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Applications of Raman Spectroscopy in Mineralogy and Geochemistry

By and

The application of Raman spectroscopy for the identification and characterization of minerals and related materials has increased appreciably during recent years. Raman spectroscopy has proven to be a most valuable and versatile analytical tool. Successful applications cover virtually all the mineralogical sub-disciplines, and have become more numerous in geochemistry. We present a general summary of present applications, illustrated by selected examples. In addition, we briefly point out several aspects of spectral acquisition, data reduction, and interpretation of Raman results that are important for the application of Raman spectroscopy as a reliable analytical tool.

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Applications of Raman Spectroscopy in Metamorphic Petrology and Tectonics

By , and

Raman spectroscopy is widely applied in metamorphic petrology and offers many opportunities for geological and tectonic research. Minimal sample preparation preserves sample integrity and microtextural information, while use with confocal microscopes allows spatial resolution down to the micrometer level. Raman spectroscopy clearly distinguishes mineral polymorphs, providing crucial constraints on metamorphic conditions, particularly ultrahigh-pressure conditions. Raman spectroscopy can also be used to monitor the structure of carbonaceous material in metamorphic rocks. Changes in structure are temperature-sensitive, so Raman spectroscopy of carbonaceous material is widely used for thermometry. Raman spectroscopy can also detect and quantify strain in micro-inclusions, offering new barometers that can be applied to understand metamorphic and tectonic processes without any assumptions about chemical equilibrium.

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Geoscience Meets Biology: Raman Spectroscopy in Geobiology and Biomineralization

By , and

Raman spectroscopy is widely applied in metamorphic petrology and offers many opportunities for geological and tectonic research. Minimal sample preparation preserves sample integrity and microtextural information, while use with confocal microscopes allows spatial resolution down to the micrometer level. Raman spectroscopy clearly distinguishes mineral polymorphs, providing crucial constraints on metamorphic conditions, particularly ultrahigh-pressure conditions. Raman spectroscopy can also be used to monitor the structure of carbonaceous material in metamorphic rocks. Changes in structure are temperature-sensitive, so Raman spectroscopy of carbonaceous material is widely used for thermometry. Raman spectroscopy can also detect and quantify strain in micro-inclusions, offering new barometers that can be applied to understand metamorphic and tectonic processes without any assumptions about chemical equilibrium.

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New Trends in Raman Spectroscopy: From High-Resolution Geochemistry to Planetary Exploration

By

This article reviews nonconventional Raman spectroscopy techniques and discusses present and future applications of these techniques in the Earth and planetary sciences. Time-resolved spectroscopy opens new ways to limit or exploit luminescence effects, whereas techniques based on coherent anti-Stokes Raman scattering (CARS) or surface-enhanced Raman spectroscopy (SERS) allow the Raman signal to be considerably enhanced even down to very high spatial resolutions. In addition, compact portable Raman spectrometers are now routinely used out of the laboratory and are even integrated to two rovers going to Mars in the near future.

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