Deciphering fluid inclusions in high-grade rocks

Year:

2014

Type of Publication:

Article

Keywords:

Fluid inclusions

Authors:

van den Kerkhof, Alfons; Kronz, Andreas; Simon, Klaus

Journal:

Geoscience Frontiers

Volume:

5

Number:

5

Pages:

683 - 695

ISSN:

1674-9871

BibTex:

@article{vandenKerkhof2014683, author = "van den Kerkhof, Alfons and Andreas Kronz and Klaus Simon", abstract = "Abstract The study of fluid inclusions in high-grade rocks is especially challenging as the host minerals have been normally subjected to deformation, recrystallization and fluid-rock interaction so that primary inclusions, formed at the peak of metamorphism are rare. The larger part of the fluid inclusions found in metamorphic minerals is typically modified during uplift. These late processes may strongly disguise the characteristics of the “original” peak metamorphic fluid. A detailed microstructural analysis of the host minerals, notably quartz, is therefore indispensable for a proper interpretation of fluid inclusions. Cathodoluminescence (CL) techniques combined with trace element analysis of quartz (EPMA, LA-ICPMS) have shown to be very helpful in deciphering the rock-fluid evolution. Whereas high-grade metamorphic quartz may have relatively high contents of trace elements like Ti and Al, low-temperature re-equilibrated quartz typically shows reduced trace element concentrations. The resulting microstructures in \{CL\} can be basically distinguished in diffusion patterns (along microfractures and grain boundaries), and secondary quartz formed by dissolution-reprecipitation. Most of these textures are formed during retrograde fluid-controlled processes between ca. 220 and 500 °C, i.e. the range of semi-brittle deformation (greenschist-facies) and can be correlated with the fluid inclusions. In this way modified and re-trapped fluids can be identified, even when there are no optical features observed under the microscope. ", doi = "http://dx.doi.org/10.1016/j.gsf.2014.03.005", issn = "1674-9871", journal = "Geoscience Frontiers ", keywords = "Fluid inclusions", note = "\{SPECIAL\} ISSUE: The role of fluids in the lower crust and upper mantle: A tribute to Jacques Touret ", number = "5", pages = "683 - 695", title = "{D}eciphering fluid inclusions in high-grade rocks ", url = "http://www.sciencedirect.com/science/article/pii/S1674987114000395", volume = "5", year = "2014", }

Note:

\{SPECIAL\} ISSUE: The role of fluids in the lower crust and upper mantle: A tribute to Jacques Touret

Abstract:

Abstract The study of fluid inclusions in high-grade rocks is especially challenging as the host minerals have been normally subjected to deformation, recrystallization and fluid-rock interaction so that primary inclusions, formed at the peak of metamorphism are rare. The larger part of the fluid inclusions found in metamorphic minerals is typically modified during uplift. These late processes may strongly disguise the characteristics of the “original” peak metamorphic fluid. A detailed microstructural analysis of the host minerals, notably quartz, is therefore indispensable for a proper interpretation of fluid inclusions. Cathodoluminescence (CL) techniques combined with trace element analysis of quartz (EPMA, LA-ICPMS) have shown to be very helpful in deciphering the rock-fluid evolution. Whereas high-grade metamorphic quartz may have relatively high contents of trace elements like Ti and Al, low-temperature re-equilibrated quartz typically shows reduced trace element concentrations. The resulting microstructures in \{CL\} can be basically distinguished in diffusion patterns (along microfractures and grain boundaries), and secondary quartz formed by dissolution-reprecipitation. Most of these textures are formed during retrograde fluid-controlled processes between ca. 220 and 500 °C, i.e. the range of semi-brittle deformation (greenschist-facies) and can be correlated with the fluid inclusions. In this way modified and re-trapped fluids can be identified, even when there are no optical features observed under the microscope.