Petrogenetic relations among titanium‐rich minerals in an anatectic high‐<i>P</i> mafic granulite

Benowitz, Jeffrey A.; Kelly, E. D.

doi:10.1111/jmg.12252

Cited by 29 publications

(6 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Distributions of edge‐to‐edge matching COR may be tested as petrogenetic and tectonic indicators in a wide variety of igneous and high‐ P / T metamorphic rocks containing exsolved LAMs in garnet. Precipitates in garnet in UHT rocks (e.g., Das et al, 2013; Liu et al, 2010; Shinevar et al, 2021), high‐pressure granulites (e.g., Keller & Ague, 2018; Marsh & Kelly, 2017), eclogites (e.g., Aulbach, 2020; Ye et al, 2000), UHP rocks (e.g., Axler & Ague, 2015; Mposkos & Kostopoulos, 2001), mantle xenoliths (e.g., Alifirova et al, 2015; Haggerty & Sautter, 1990; Sakamaki et al, 2016) and crustal xenoliths (e.g., Ducea et al, 2020; Farmer et al, 2005) together offer an extensive network of diverse formation environments in which to test hypotheses of factors affecting edge‐to‐edge matching COR formation. If some edge‐to‐edge matching COR form only, for example, during exsolution at high temperatures, or in highly strained samples, such indicators would prove valuable additions to the analytical techniques used to interrogate extreme metamorphism and processes in the deep lithosphere and asthenosphere.…”

Section: Discussionmentioning

confidence: 99%

Predicting and explaining crystallographic orientation relationships of exsolved precipitates in garnet using the edge‐to‐edge matching model

Keller

Ague

2022

Journal Metamorphic Geology

View full text Add to dashboard Cite

Relative alignments of mineral exsolutions and their host crystals can be described by crystallographic orientation relationships (COR). Exsolved phases in garnet from high-grade metamorphic rocks and igneous rocks may have COR, but the complexity of COR distributions has thus far restricted their use to identifying exsolved phases. Classification of COR also remains mineral-specific, leaving doubt as to what information COR preserve. To test how COR may be standardized, we calculated mismatch of low-index crystallographic planes (d-value ratios) and crystallographic directions (rows of atoms) between precipitates and garnet and defined search criteria for structural alignments likely to be energetically favourable. We analysed published electron backscatter diffraction (EBSD) data for apatite, rutile, ilmenite, corundum, and quartz precipitates in garnet (n tot = 1,296) for the presence of these alignments. Our method predicts between 88% and 98% of observed alignments across the studied minerals and requires only calculations using unit cell parameters. We further show that each exsolved mineral forms COR predicted by the edgeto-edge matching model which was developed to describe unambiguous exsolution textures in alloys. Edge-to-edge matching aligns atoms at the hostprecipitate interface by parallelism or near-parallelism of crystallographic planes of similar spacing and parallelism of crystallographic directions (rows of atoms) of similar length on the edges of those planes. Edge-to-edge matches likely facilitate coherent to semi-coherent interfaces by lowering surface free energy and strain energy, stabilizing precipitates. These matches are defined by criteria applicable to all minerals, making them an ideal tool for classifying, discovering and interpreting COR of diverse precipitates in garnet. This approach may also predict COR in other geological mineral pairs (e.g., exsolved feldspars). We find that edge-to-edge matching may explain the stability of the needle-shaped morphologies commonly observed for exsolution textures in garnet. Edge-to-edge matching COR distributions can be tested as proxies of the state of the host rock at the time of exsolution to evaluate factors such as temperature, cooling rate, degree of undercooling, and/or strain. Patterns of edge-to-edge matching COR may be paired with

show abstract

Section: Discussionmentioning

confidence: 99%

Predicting and explaining crystallographic orientation relationships of exsolved precipitates in garnet using the edge‐to‐edge matching model

Keller

Ague

2022

Journal Metamorphic Geology

View full text Add to dashboard Cite

show abstract

“…The reactant phase is not preserved within the symplectite. Symplectitic intergrowth of ilmenite + clinopyroxene is not commonly reported; however, titanite replaced by ilmenite + clinopyroxene has been described from retrogressed eclogites and HP granulites elsewhere (Carswell et al, 1996;O'Brien and Rötzler, 2003;Faryad et al, 2006;Marsh and Kelly, 2017). The zoning is characterized by a slight rimward increase in Mn and Fe and a decrease in Mg.…”

Section: Precursor Of Ilmenite + Clinopyroxene Symplectitementioning

confidence: 99%

“…The intergrowths are further assumed to have formed by allochemical reactions between titanite and adjacent garnets. Anatectic HP mafic granulites from the Grenville Province, Ontario, contain large titanite grains mantled by finegrained ilmenite + clinopyroxene symplectite (Marsh and Kelly, 2017). Formation of the symplectite is related to decompression at high temperature (ca.…”

Section: Precursor Of Ilmenite + Clinopyroxene Symplectitementioning

confidence: 99%

Symplectite and kelyphite formation during decompression of mafic granulite from Gjelsvikfjella, central Dronning Maud Land, Antarctica

Elvevold,

Jacobs,

Pedersen

et al. 2023

Eur. J. Mineral.

View full text Add to dashboard Cite

Abstract. Central Dronning Maud Land (cDML) is part of the late Mesoproterozoic Maud Belt in East Antarctica, which was metamorphosed and deformed during the Ediacaran–Cambrian Gondwana assembly. Here we study high-pressure (HP) mafic rocks in Gjelsvikfjella, cDML, which occur as lenses and pods transposed in highly strained, upper amphibolite-facies gneisses. We present a P–T–t history for the HP rocks based on mineral assemblages, reaction textures and new U–Pb zircon data. Relics that indicate an early HP granulite-facies stage have been identified in anhydrous garnet–clinopyroxene rocks. The peak-pressure assemblage was plagioclase-free and contained garnet, titanite, clinopyroxene and quartz. The HP assemblage has been extensively overprinted by lower-pressure phases and exhibits a variety of symplectite and corona textures that record the post-peak-pressure evolution of the rocks. Decompression and heating in the granulite-facies field resulted in the replacement of titanite by ilmenite–clinopyroxene symplectite, formation of clinopyroxene–plagioclase intergrowths and resorption of garnet by plagioclase–clinopyroxene kelyphite. Formation of late orthopyroxene in symplectites and kelyphites demonstrates that the P–T evolution entered the medium-pressure granulite-facies field. The peak metamorphic stage was followed by retrograde cooling into the amphibolite facies. In situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating of zircons indicate Mesoproterozoic protolith ages (1150–1000 Ma) and Ediacaran–Cambrian metamorphic reworking at ca. 568 and ca. 514 Ma. The HP granulites were formed and exhumed during a clockwise P–T evolution related to continental collision during Gondwana amalgamation, followed by post-collisional extension and orogenic collapse.

show abstract

“…(Matthews & Goldsmith, 1984); (iii) clinopyroxene + ilmenite intergrowths after titanite, e.g. (Faryad et al, 2006(Faryad et al, , 2010Marsh & Kelly, 2017;Marsh & Smye, 2017;O'Brien & Rötzler, 2003), and (iv) orthopyroxene + plagioclase after garnet, e.g. (O'Brien & Rötzler, 2003).…”

Section: Pressure-temperature-time Evolutionmentioning

confidence: 99%

Rare allanite in granulitised eclogites constrains timing of eclogite to granulite facies transition in the Bhutan Himalaya

Wood¹,

Warren²,

Argles³

et al. 2024

Preprint

View full text Add to dashboard Cite

During continental collision, crustal rocks are buried, deformed, transformed and exhumed. The rates, timescales and tectonic implications of these processes are determined by linking geochemical, geochronological and microstructural data from metamorphic rock-forming and accessory minerals. Exposures of lower orogenic crust provide important insights into orogenic evolution, but are rare in young continental collision belts such as the Himalaya. In NW Bhutan, eastern Himalaya, a high-grade metamorphic terrane provides a rare glimpse into the evolution and exhumation of the deep eastern Himalayan crust and a detailed case study for deciphering the rates and timescales of deep-crustal processes in orogenic settings. We have collected U-Pb isotope and trace element data from allanite, zircon and garnet from metabasite boudins exposed in the Masang Kang valley in NW Bhutan. Our observations and data suggest that allanite cores record growth under eclogite facies conditions (>17 kbar ~650°C) at ca. 19 Ma, zircon inner rims and garnet cores record growth during decompression under eclogite facies conditions at ca 17-15.5. Ma, and symplectitic allanite rims, garnet rims and zircon outer rims record growth under granulite facies conditions at ~9-6 kbar; >750°C at ca. 15-14.5 Ma. Allanite is generally considered unstable under granulite-facies conditions and we think that this is the first recorded example of such preservation, likely facilitated by rapid exhumation. Our new observations and petrochronological data show that the transition from eclogite to granulite facies conditions occurred within 4-5 Ma in the Eastern Himalaya. Our data indicate that the exhumation of lower crustal rocks across the Himalaya was diachronous and may have been facilitated by different tectonic mechanisms.

show abstract

Petrogenetic relations among titanium‐rich minerals in an anatectic high‐P mafic granulite

Cited by 29 publications

References 62 publications

Predicting and explaining crystallographic orientation relationships of exsolved precipitates in garnet using the edge‐to‐edge matching model

Predicting and explaining crystallographic orientation relationships of exsolved precipitates in garnet using the edge‐to‐edge matching model

Symplectite and kelyphite formation during decompression of mafic granulite from Gjelsvikfjella, central Dronning Maud Land, Antarctica

Rare allanite in granulitised eclogites constrains timing of eclogite to granulite facies transition in the Bhutan Himalaya

Contact Info

Product

Resources

About