Intrusive origin for Upper Group (UG1, UG2) stratiform chromitite seams in the Dwars River area, Bushveld Complex, South Africa

Voordouw, R.J.; Gutzmer, Jens; Beukes, Nicolas J.

doi:10.1007/s00710-009-0072-3

Cited by 114 publications

(17 citation statements)

References 63 publications

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“…The two underlying thin chromitite seams bifurcate from a single layer at the right hand side of the photo along strike ( Fig. 2.1f; Voordouw et al 2009;Lee 1981). Many chromitite seams preserve sedimentary-like features, such as graded bedding, braiding and slump structures, and can contain angular xenoliths of the surrounding cumulate rocks ( Fig.…”

Section: Formation Of Chromitite Layersmentioning

confidence: 96%

“…Many chromitite seams preserve sedimentary-like features, such as graded bedding, braiding and slump structures, and can contain angular xenoliths of the surrounding cumulate rocks ( Fig. 2.12; Voordouw et al 2009). Despite modification due to subsolidus recrystallization, textural analysis reveals that chromite sometimes formed as an early cumulus phase, and in other cases occurs in the interstices of cumulus olivine (the latter often altered to serpentine), pyroxene or plagioclase.…”

Section: Formation Of Chromitite Layersmentioning

confidence: 99%

“…In particular, the length-scales and mechanisms of chromite transport and remobilization prior to solidification remain debated (in-situ settling, with or without subsequent thickening, or long distance transport of chromite-laden slurries; e.g. Voordouw et al 2009;Naldrett et al 2012). All these suggest that chromitite formation needs not be restricted to a single mechanism; it is conceivable, and even likely, that a range of different processes are conducive to forming chromitite.…”

Section: Formation Of Chromitite Layersmentioning

confidence: 99%

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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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Section: Formation Of Chromitite Layersmentioning

confidence: 96%

Section: Formation Of Chromitite Layersmentioning

confidence: 99%

Section: Formation Of Chromitite Layersmentioning

confidence: 99%

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Igneous Layering in Basaltic Magma Chambers

et al. 2015

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“…Layered mafic intrusions and their stratiform Fe-Ti oxide and chromitite layers are very significant for understanding the chemical processes and physical mechanisms of magmatic evolution in a large, sheet-like magma chamber [e.g., Wager and Brown, 1967;Irvine and Sharpe, 1986;and references therein]. It is widely accepted that the formation of chromitite layers in layered intrusions is associated with fractional crystallization or magma mixing [Irvine, 1977;Eales, 2000;Mondal and Mathez, 2007;Voordouw et al, 2009;Naldrett et al, 2012]. However, although the Fe-Ti oxide layers in layered intrusions are commonly interpreted as accumulations of Fe-Ti oxides in late magmatic fractionation stages [Wager and Brown, 1967;Klemm et al, 1985], some researchers have argued that they are associated with a Fe-rich immiscible liquid segregated from mafic magma [Bateman, 1951;Reynolds, 1985;von Gruenewaldt, 1993;Zhou et al, 2005]; magma addition and/or mixing [Harney et al, 1990]; change in oxygen content [Klemm et al, 1985]; or change in pressure [Cawthorn and McCarthy, 1980].…”

Section: Introductionmentioning

confidence: 99%

Formation of thick stratiform Fe‐Ti oxide layers in layered intrusion and frequent replenishment of fractionated mafic magma: Evidence from the Panzhihua intrusion, SW China

Song

et al. 2013

Geochem Geophys Geosyst

132

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The Panzhihua intrusion is one of the largest layered intrusions that hosts huge stratiform Fe‐Ti oxide layers in the central part of the Emeishan large igneous province, SW China. Up to 60 m thick stratiform massive Fe‐Ti oxide layers containing ~85 modal% of magnetite and ilmenite and overlying magnetite gabbro compose cyclic units of the Lower Zone of the intrusion. The cyclic units of the Middle Zone consist of magnetite gabbro and overlying gabbro. In these cyclic units, contents of Fe2O3(t), TiO2 and Cr and Fe3+/Ti4+ ratio of the rocks decrease upward, Cr content of magnetite and forsterite percentage of olivine decrease as well. The Upper Zone consists of apatite gabbro characterized by enrichment of incompatible elements (e.g., 12–18 ppm La, 20–28 ppm Y) and increasing of Fe3+/Ti4+ ratio (from 1.3 to 2.3) upward. These features indicate that the Panzhihua intrusion was repeatedly recharged by more primitive magma and evolved magmas had been extracted. Calculations using MELTS indicate that extensive fractionation of olivine and clinopyroxene in deep level resulted in increasing Fe and Ti contents in the magma. When these Fe‐Ti‐enriched magmas were emplaced along the base of the Panzhihua intrusion, Fe‐Ti oxides became an early crystallization phase, leading to a residual magma of lower density. We propose that the unusually thick stratiform Fe‐Ti oxide layers resulted from coupling of gravity settling and sorting of the crystallized Fe‐Ti oxides from Fe‐Ti‐enriched magmas and frequent magma replenishment along the floor of the magma chamber.

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“…Figures 8 to 10 show the micrographs of chromitite before and after heat treatment at different temperatures. Voordouw, Gutzmer, and Beukes (2009) reported the average modal mineral abundance for the UG1 and UG2 seams (Table I). Schouwstra, Kinloch, and Lee (2000) stated that UG2 consists predominantly of chromite (60 to 90 vol.%), with lesser silicate minerals (5 to 30% pyroxene and 1 to 10% plagioclase), while other minerals are present in minor concentrations.…”

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confidence: 99%