Application of titanium-in-quartz geothermometry to magmatic quartz in evolved rocks from the Bushveld Complex, South Africa

Buthelezi, Mbongiseni; Ashwal, Lewis D.; Horváth, Péter

doi:10.25131/gssajg.120.2.241

Cited by 2 publications

(1 citation statement)

References 27 publications

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“…These high temperatures are instead much more likely to be associated with Bushveld magmatism. One study from the Northern Limb of the Bushveld Complex suggests a mean solidus temperature for the cumulate rocks of 732 ± 31 • C [105]. Thus, deformation during compaction at temperatures close to the solidus is the most likely cause of the observed features.…”

Section: Textural Modification Through Compactionmentioning

confidence: 97%

The Merensky Cyclic Unit, Bushveld Complex, South Africa: Reality or Myth?

2018

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The Merensky Unit, Bushveld Complex, is commonly described using genetic terms such as "cyclic unit", typically without careful consideration of the connotations. We suggest that this contributes to the debate on processes forming the unit. This study integrates an extensive field study with detailed petrographic and textural analyses of the Merensky Unit to determine whether it is a "cyclic unit" sensu stricto. The study indicates that the bulk of the platinum-bearing chromitite-feldspathic orthopyroxenite developed through heterogeneous nucleation and in situ growth during multiple replenishment events. The overlying leuconorite developed above a gradational boundary, reflecting mixing following replenishment by a relatively more evolved magma. The bulk of this unit also formed in situ. The uppermost poikilitic anorthosite formed above a distinct boundary through a subsequent injection of a plagioclase-saturated magma, which crystallised in situ. Processes of gravitational settling and local remobilisation of crystals cannot be discounted from contributing to the development of the unit. The final textures throughout the unit developed through pervasive textural equilibration, with extensive fluid-mediated textural equilibration forming the megacrystic feldspathic orthopyroxenite. The evidence for at least five replenishment events indicates that the Merensky Unit is not a cyclic unit; therefore, the genetic term, "Merensky Cyclic Unit", is misleading and its use should be carefully considered in future work.

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Section: Textural Modification Through Compactionmentioning

confidence: 97%

The Merensky Cyclic Unit, Bushveld Complex, South Africa: Reality or Myth?

2018

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Texture and Trace Element Geochemistry of Quartz: A Review

et al. 2022

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Quartz is one of the most abundant minerals. Used in a variety of materials, it preserves geological history and reflects alteration conditions. Data were collected (>2400 data points) from more than 40 ore deposits to understand its internal texture and geochemistry. Cathodoluminescence imaging is a technique for examining the internal texture of quartz that may reveal information about the crystal’s origin and evolution. The dominant trace elements in quartz lattice are Al, P, Li, Ti, Ge, K, and Na. These, combined with internal texture, can distinguish quartz from different origins and can differentiate between different types of ore deposits, as each type of ore deposit has its own unique CL characteristics. Therefore, Al did not correlate with cathodoluminescence (CL) in epithermal Au-Sb-Hg, Carlin-type Au, epithermal Ag, or shale-hosted Zn deposits. Epithermal base metal and porphyry-Cu-type deposits were intermediate, and Mississippi-Valley-type, epithermal Au-Ag, and porphyry Cu-Mo deposits were characterized for Al correlation with CL. Furthermore, Gigerwald, Rohdenhaus, and Westland deposits had Li/Al ratios less than one, suggesting that H (as hydroxyl substituting for oxygen) completed the charge. However, trace elements (i.e., Ge, Sb, Ti, and Al), sector zoning, and resorption surfaces were vital parameters to differentiate between magmatic and hydrothermal quartz. Additionally, titanium and aluminum were the most important trace elements. Their values could be used to differentiate between different quartz types. Among them, hydrothermal and pegmatitic quartz were characterized by lower temperatures and Ti concentrations. Rhyolitic quartz was characterized by the lowest Al, the highest temperatures, and lower Al/Ti ratios. Aluminum, Li, and H were most important in hydrothermal and metamorphic quartz, but magmatic quartz was generally enriched with Ti.

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Application of titanium-in-quartz geothermometry to magmatic quartz in evolved rocks from the Bushveld Complex, South Africa

Cited by 2 publications

References 27 publications

The Merensky Cyclic Unit, Bushveld Complex, South Africa: Reality or Myth?

The Merensky Cyclic Unit, Bushveld Complex, South Africa: Reality or Myth?

Texture and Trace Element Geochemistry of Quartz: A Review

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