Silicate Liquid Immiscibility in Layered Intrusions

Abstract

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:

Silicate liquid immiscibility in impact melts

“…The thermodynamics of phase separation are detailed elsewhere (e.g., James ; Wood and Hess ; Hess ; Shelby ; Veksler and Charlier ). Briefly, melt unmixing is governed by the melt’s Gibbs free energy of mixing, Δ G m , which is given bywhere Δ H m is the enthalpy of mixing, T is the temperature, and Δ S m is the entropy of mixing.…”

“…Binodal and spinodal in a schematic binary system A–B, modified after Veksler and Charlier (). a) Gibbs free energy of mixing Δ G m versus composition X curves for temperatures above ( T 1 ; curve 3), at ( T c ; curve 2), and below ( T 2 ; curve 1) the consolute temperature of the system.…”

“…, ; Charlier et al. , ; Charlier and Grove ; Veksler and Charlier ). In conclusion, to this day there is disagreement as to the importance of silicate liquid immiscibility for magmatic evolution.…”

Immiscible iron- and silica-rich liquids in the Upper Zone of the Bushveld Complex

“…Philpotts, 1982;Charlier et al, 2013) and in plutonic environments (e.g. Jakobsen et al, 2005;Namur et al, 2012;Kamenetsky et al, 2013;Veksler and Charlier, 2015). In the case of the Bushveld Complex, South Africa (Fig.…”

Stable and metastable silicate liquid immiscibility in ferrobasalts

“…The formation of immiscible silica-rich and iron-rich melts during cooling of ferrobasalts has been recognized experimentally and in plutonic and volcanic rocks (Philpotts 1982;Charlier and Grove 2012;Veksler and Charlier 2015). However, unmixing of immiscible melts under equilibrium conditions (binodal above the liquidus) or as a metastable process (binodal below the liquidus) has long been discussed.…”