Textural coarsening in igneous rocks

Higgins, Michael D.

doi:10.1080/00206814.2010.496177

Cited by 121 publications

(57 citation statements)

References 57 publications

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“…Some adcumulates, cumulates with only minor postcumulus material (Irvine 1987), may also have formed directly on the surface of the cumulate pile (Campbell et al 1983;Campbell 1987). Crystal ageing (Boudreau 2011) and textural coarsening (Higgins 2011;Higgins (Chap. 3, Quantitative textural analysis of rocks in layered mafic intrusions)) may also modify the final texture of a cumulate.…”

Section: Cumulates and Geochronologymentioning

confidence: 99%

Geochronology of Layered Intrusions

Scoates

Wall

2015

Springer Geology

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Layered intrusions crystallize mainly from basaltic magma to form large bodies of igneous rocks that exhibit prominent layering and they preserve stunning rock records of the processes by which magma evolves in crustal magma chambers. These intrusions contain world-class deposits of chromium, platinum group elements (PGE), and vanadium, metals that are vital to industry and society in general. Despite their scientific and practical importance, precise age constraints are lacking for many layered intrusions, and geochronological frameworks linking crystallization and cooling ages for the most part do not exist. This has resulted in critical knowledge gaps related to their origin and formation. This chapter provides an overview of dating methods (U-Th-Pb, 40 Ar/ 39 Ar) and mineral chronometers (e.g., zircon, baddeleyite, rutile, apatite, titanite) potentially present in layered intrusions that is coupled with field, textural, and petrographic criteria for targeting sample selection to allow for the successful implementation of geochronologic studies of layered mafic-ultramafic rocks of any age. As an application, we demonstrate how the thermal history of the Bushveld Complex is documented by mineral ages from samples of the PGE-rich Merensky Reef. High-precision U-Pb zircon ages, involving pretreatment of zircon by the chemical abrasion (annealing and leaching) or CA-TIMS technique, for two samples separated by > 300 km are indistinguishable from each other (2056.88 ± 0.41 Ma, Eastern Limb; 2057.04 ± 0.55 Ma, Western Limb; uncertainty reported as 2s) confirming synchronous crystallization of this horizon at near-solidus conditions across the intrusion. Rapid cooling (~ 125 °C/Ma) down to temperatures of ~ 400-450 °C is defined by U-Pb rutile ages from the same samples (2052( .96 ± 0.61 Ma, 2053.0 ± 2.7 Ma) and a regional hydrothermal event is signaled in 40 Ar/ 39 Ar biotite ages (1999 ± 10 Ma, 2002 ± 10 Ma). The geochronology of layered intrusions, where magma differentiation processes are captured in a wide range of rock textures and structures, represents an essential tool for assessing the evolution of mafic magmatism in the Earth's crust.

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Section: Cumulates and Geochronologymentioning

confidence: 99%

Geochronology of Layered Intrusions

Scoates

Wall

2015

Springer Geology

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“…It is proposed that layering developed by dissipation of crystal surface energy during equilibration (Higgins 2011), the same mechanism that is credited with creating the 'inch scale' layering at Stillwater (Boudreau 1987). It is generally thought that such a mechanism needs the temperature to be maintained close to the liquidus for a long period of time, and hence that it rarely occurs in small intrusions.…”

Section: Layering By Grain Coarsening and Changing Liquid Compositionmentioning

confidence: 99%

Igneous Layering in Basaltic Magma Chambers

et al. 2015

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PrefaceLayered intrusions have received continuous interest since the publication of the treatise on 'Layered Igneous Rocks' by Lawrence Wager and Malcolm Brown, updated in books edited by Ian Parsons in 1987 and Grant Cawthorn in 1996. The study of these fossilized magma chambers keep inspiring a number of scientists with a range of interests including petrology and igneous differentiation, geochronology, geochemistry, mineralogy, rock textures and fabric, fluid dynamics, and ore deposits. The goal of this book is to further our understanding of magma chamber processes and crystal-liquid relationship during magma cooling magma. Physical and chemical processes are now better quantified thanks to the development analytical and computing tools such as compositional mapping, 3D X-ray computed tomography, in situ analyses for trace elements and isotopes, development of new experimental facilities, and progress in instrument sensitivity.The book is subdivided into two parts. The first includes reviews and new views on chronological, textural, mineralogical, geochemical, and magnetic characteristics of layered igneous rocks. The second part reviews recent progress in the study of layered intrusions. A newcomer on the layered intrusions scene is the Panzhihua intrusion (SW China) that has been intensively studied recently. Reviews of recent findings for Sept Iles, Bushveld, Kiglapait, Ilímaussaq, and layered rocks in ophiolites are also presented. Interest in layered intrusions is also driven by their natural resources. Many intrusions host world-class ore bodies of chromium, platinum group elements (PGE), vanadium, titanium and phosphorous. Ore-forming processes and important deposits associated with layered intrusions are described and their origin is discussed.The objective of this book is to outline the most recent ideas and challenges in the study of layered igneous bodies. It has also the purpose to aid in teaching, and to encourage new studies to tackle major issues in the understanding of magma chamber processes and associated ore-forming processes.The book has benefited from detailed comments by a many reviewers, who are greatly acknowledged:

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“…Textural equilibration (relaxation) is probably one of the most important processes in igneous petrology, and its effects are increasingly recognized (Higgins 2011b). Initial growth at higher degrees of undercooling produces a texture in which crystals have a range of sizes and impinge on each other at random angles (Fig.…”

Section: Textural Equilibrationmentioning

confidence: 99%

Igneous Rock Associations 17. Advances in the Textural Quantification of Crystalline Rocks

Higgins

2015

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SUMMARYDuring the last 20 years, textural (microstructural) studies have regained their place in the pantheon of petrographic methods. This has happened by quantifying textures, so that models can be developed and tested -an approach that has proved to be so successful for chemical and isotopic studies. The combination of chemical, isotopic and textural methods, especially if applied to different crystal populations, can be a very powerful tool in the clarification of petrologic histories of rocks. Here, I will discuss some recent advances in the application of textural studies to crystalline rocks. RÉSUMÉAu cours des 20 dernières années, les études de texture (microstructure) ont retrouvé leur place au panthéon des méthodes pétrographiques. Cela a pu se produire grâce à la quantification des textures, permettant ainsi de développer et tester des modèles -une approche qui s'est avérée très béné-fique pour les études chimiques et isotopiques. La combinaison de méthodes chimiques, isotopiques et d'analyse texturale, en particulier si elles sont appliquées à des populations distinctes de cristaux, peut être un outil très puissant permettant de définir l'histoire pétrologique des roches. Dans le présent article, je vais discuter de certaines percées récentes dans l'application d'études texturales de roches cristallines.Traduit par le Traducteur INTRODUCTION Petrography started in the 19 th century with the development of the petrographic microscope ( Fig. 1; Kile 2003). Initial observations were qualitative, except for modal measurements. However, the development of quantitative chemical and isotopic analysis in the 20 th century somewhat eclipsed traditional petrographic studies and has come to dominate petrology. This is understandable: quantitative measurements do enable more rigorous testing of petrologic models. However, petrography started to regain lost ground about 25 years ago, when quantitative materials science methodology was first applied to petrologic problems (e.g. Cashman and Marsh 1988). Many of the best studies now use a combination of geochemical, isotopic and textural approaches (see review in Higgins 2006).As with all analytical methods, the scale of observation, which can also be considered as the analytical volume, is dictated by the methods used and will provide information on different aspects of the petrological evolution of the rock. For instance, a whole rock chemical analysis provides data on a large volume of material whereas microprobe analyses convey information about individual crystals or parts of crystals. In a similar way, some textural analysis methods supply information on whole crystal populations, whereas others can inform us on individual crystals.There are many definitions of rock texture (microstructure), but the simplest is the geometric arrangement of crystals or other structures in a rock. This is a 'crystal map,' in the sense that it is a simplified representation of the actual structure of a rock. Such maps are actually three dimensional, but are commonly measured or r...

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Textural coarsening in igneous rocks

Cited by 121 publications

References 57 publications

Geochronology of Layered Intrusions

Geochronology of Layered Intrusions

Igneous Layering in Basaltic Magma Chambers

Igneous Rock Associations 17. Advances in the Textural Quantification of Crystalline Rocks

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