An Early Cretaceous garnet pressure–temperature path recording synconvergent burial and exhumation from the hinterland of the Sevier orogenic belt, Albion Mountains, Idaho

Kelly, E. D.; Hoisch, Thomas D.; Wells, Michael L.; Vervoort, Jeffrey D.; Beyene, Mengesha

doi:10.1007/s00410-015-1171-2

Cited by 27 publications

(28 citation statements)

References 77 publications

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“…Garnet is present in many textures and has been extensively used to decipher complex mineral growth–deformation relationships (e.g. Cutts et al, ; George & Gaidies, ; Kelly, Hoisch, Wells, Vervoort, & Beyene, ; Thigpen et al, ). Garnet commonly shows heterogeneous non‐equilibrium compositions, most commonly with a continuous chemical core–rim zonation.…”

Section: Introductionmentioning

confidence: 99%

Decoding the complex internal chemical structure of garnet porphyroblasts from the Zermatt area, Western Alps

Bucher

Weisenberger

Klemm³

et al. 2019

Journal Metamorphic Geology

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Garnet is a prototypical mineral in metamorphic rocks because it commonly preserves chemical and textural features that can be used for untangling its metamorphic development. Large garnet porphyroblasts may show extremely complex internal structures as a result of a polycyclic growth history, deformation, and modification of growth structures by intra‐ and intercrystalline diffusion. The complex internal structure of garnet porphyroblasts from garnet–phengite schists (GPS) of the Zermatt area (Western Alps) has been successfully decoded. The centimetre‐sized garnet porphyroblasts are composed of granulite facies garnet fragments overgrown by a younger generation of grossular‐rich eclogite facies garnet. The early granulite facies garnet (G‐Grt) formed from low‐P, high‐T metamorphism during a pre‐Alpine orogenic event. The late garnet (E‐Grt) is typical of high‐pressure, low‐temperature (HPLT) metamorphism and can be related to Alpine subduction of the schists. Thus, the garnet of the GPS are polycyclic (polymetamorphic). G‐Grt formation occurred at ~670 MPa and 780°C, E‐Grt formed at ~1.7 GPa and 530°C. The G‐Grt is relatively rich in Prp and poor in Grs, while E‐Grt is rich in Grs and poor in Prp. The Alm content (mol.%) of G‐Grt is 68 of E‐Grt 55. After formation of E‐Grt between and around fragmented G‐Grt at 530°C, the GPS have been further subducted and reached a maximum temperature of 580°C before exhumation started. Garnet composition profiles indicate that the initially very sharp contacts between the granulite facies fragments of G‐Grt and fracture seals of HPLT garnet (E‐Grt) have been modified by cation diffusion. The profiles suggest that Ca did not exchange at the scale of 1 µm, whereas Fe and Mg did efficiently diffuse at the derived maximum temperature of 580°C for the GPS at the scale of 7–8 µm. The Grt–Grt diffusion profiles resulted from spending c. 10 Ma at 530–580°C along the P–T–t path. The measured Grt composition profiles are consistent with diffusivities of log DMgFe = −25.8 m2/s from modelled diffusion profiles. Mg loss by diffusion from G‐Grt is compensated by Fe gain by diffusion from E‐Grt to maintain charge balance. This leads to a distinctive Fe concentration profile typical of uphill diffusion.

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Section: Introductionmentioning

confidence: 99%

Decoding the complex internal chemical structure of garnet porphyroblasts from the Zermatt area, Western Alps

Bucher

Weisenberger

Klemm³

et al. 2019

Journal Metamorphic Geology

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“…Consider that the garnet zoning models in this study are unable to record any decrease in T as, in that scenario, garnet is consumed (Figures a, , and , garnet‐in line). Thus, it is possible that the garnets with N‐shaped P‐T paths actually experienced a hiatus in growth during a decrease in T (and/or P; e.g., Kelly et al, ). In ED28 (Figure b), the Mg map shows an irregular (nonconcentric) pattern between the low concentration near the core (blue) and higher concentration in the mantle (green) that resembles the irregular rim of a partially consumed garnet.…”

Section: Discussionmentioning

confidence: 99%

“…For P‐T path modeling, bulk‐rock compositions were calculated using mineral chemistry measured in matrix phases and zoned garnets combined with estimates of phase volumes and converted to moles of elements as in Kelly et al (). Mineral modes were estimated visually from thin sections and hand samples.…”

Section: Methodsmentioning

confidence: 99%

“…The bulk compositions were used with Theriak‐Domino (de Capitani & Brown, ; de Capitani & Petrakakis, ) and the Holland and Powell () data set with updates through 2010 in the system MnO‐Na 2 O‐CaO‐K 2 O‐FeO‐MgO‐Al 2 O 3 ‐SiO 2 ‐H 2 O‐TiO 2 (MnNCKFMASHT) to generate isochemical phase diagrams representing the thermodynamic conditions at the beginning of garnet growth. Solution models are the same as in Kelly et al () and Catlos et al (). The intersection of almandine, pyrope, spessartine, and grossular concentrations (isopleths) of the apparent garnet core were used to estimate initial garnet growth conditions.…”

Section: Methodsmentioning

confidence: 99%

“…The ability to efficiently model high‐resolution changes in garnet chemical zoning offers new possibilities for acquiring precise and reliable metamorphic records from collisional tectonic locales (e.g., Catlos et al, ; Kelly et al, ; Moynihan & Pattison, , ). The Menderes Massif of western Turkey (Figure ) contains abundant garnet‐bearing metapelitic schists for which other thermobarometric techniques have produced mostly broad and uncertain constraints.…”

Section: Introductionmentioning

confidence: 99%

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Implications for Thrust‐Related Shortening Punctuated by Extension From P‐T Paths and Geochronology of Garnet‐Bearing Schists, Southern (Çine) Menderes Massif, SW Turkey

et al. 2019

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The Menderes Massif, Turkey, is a type locality for deciphering the plate tectonic response from collision‐ to extension‐driven exhumation. Conventional thermobarometry and garnet pressure‐temperature (P‐T) paths from isochemical phase diagrams were calculated across a major fault (Selimiye Shear Zone, SSZ) bounding the southern edge of the Menderes Massif. Both approaches yield similar garnet rim temperatures (from 555 to 671 °C), but estimated P differs by between 8 and 15 kbar. Three garnets north of the SSZ reveal N‐shaped P‐T paths, whereas paths from three samples south of the SSZ show a simple increase in P‐T. Monazite and zircon were dated in thin section from the same rocks using Secondary Ion Mass Spectrometry and Laser Ablation Inductively Coupled Plasma‐Mass Spectrometry, respectively. Textural relationships of monazite within garnet appears indicative of post‐garnet growth. The amount of monazite common 204Pb and 137Ba+/Th+ significantly exceeds what is observed for the monazite age standard, suggesting their ages mark fluid‐driven events, loosely constrained to Late Eocene‐Early Miocene. Some zircon ages are consistent with Cambro‐Ordovician ages reported elsewhere in the region, and other ages are Neoproterozoic and Permian‐Triassic, a period not previously recognized in this area. Despite the lack of age constraints for the duration of garnet growth, we present a thermal model to understand the meaning of the N‐shaped path. These paths are best reproduced by thermal models incorporating SSZ thrusting before and after denudation. This paper presents an example of the insight from high‐resolution P‐T paths, and an example of denudation within a prograde metamorphic event.

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Records of Himalayan Metamorphism and Contractional Tectonics in the Central Himalayas (Darondi Khola, Nepal)

Catlos

2023

Compressional Tectonics

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An Early Cretaceous garnet pressure–temperature path recording synconvergent burial and exhumation from the hinterland of the Sevier orogenic belt, Albion Mountains, Idaho

Cited by 27 publications

References 77 publications

Decoding the complex internal chemical structure of garnet porphyroblasts from the Zermatt area, Western Alps

Decoding the complex internal chemical structure of garnet porphyroblasts from the Zermatt area, Western Alps

Implications for Thrust‐Related Shortening Punctuated by Extension From P‐T Paths and Geochronology of Garnet‐Bearing Schists, Southern (Çine) Menderes Massif, SW Turkey

Records of Himalayan Metamorphism and Contractional Tectonics in the Central Himalayas (Darondi Khola, Nepal)

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