Linking thermodynamic modelling, Lu–Hf geochronology and trace elements in garnet: new P–T–t paths from the Sevier hinterland

Abstract

Major element, trace element and Lu-Hf geochronological data from amphibolite facies pelitic schist in the Raft River and Albion Mountains of northwest Utah and southern Idaho indicate that garnet grew during increasing pressure, interpreted to be the result of tectonic burial and crustal thickening during Sevier orogenesis. Garnet growth was interrupted by hiatuses interpreted from discontinuities in major element zonation. Pressure-temperature paths were determined from the pre-hiatus portions of the garnet chemical zoning profiles and indicate an increase of~2 kbar and~50°C in the western Raft River Mountains. Garnet Lu-Hf dates of 150 AE 1 Ma in the western Raft River Mountains and 138.7 AE 0.7 Ma and 132 AE 5 Ma in the southern Albion Mountains indicate the timing of garnet growth. Lutetium garnet zoning profiles indicate that the Lu-Hf ages are biased towards the posthiatus or outer pre-hiatus segments, indicating that the determined ages likely post-date the recorded P-T path history or date the tail end of the paths. Crustal thickening associated with Sevier orogenesis in the western Raft River Mountains thus began slightly before 150 AE 1 Ma, in the Late Jurassic. This study shows that integrating P-T paths determined from garnet growth zoning with Lu-Hf garnet geochronology and in situ garnet trace element analyses is an effective approach for interpreting and dating deformation events in orogenic belts.

Fault Slip and Exhumation History of the Willard Thrust Sheet, Sevier Fold‐Thrust Belt, Utah: Relations to Wedge Propagation, Hinterland Uplift, and Foreland Basin Sedimentation

“…Summary of temporal relations between thrust slip in the Sevier belt, foreland sedimentation, hinterland deformation, and arc magmatism. Available geochronologic and thermochronometric data (Naeser et al, 1983;Burtner & Nigrini, 1994;Wells et al, 2008Wells et al, , 2015Cruz-Uribe et al, 2015; this study) record overall west to east propagation of the thrusts and protracted uplift of the Wasatch anticlinorium in the Sevier belt. Relative deformation rates given by colors; lighter to darker blues indicate slower to faster shortening rates, and orange hues indicate extension.…”

“…The timing for onset of thrusting in the Sevier belt (herein taken as the region marked by thin-skinned thrusting of passive margin to platform strata, as compared to the hinterland region marked by middle to lower crustal metamorphism and thickening) has been widely debated and likely varied regionally along the length of the orogenic system (Armstrong & Oriel, 1965;DeCelles, 2004;Fuentes et al, 2009;Giallorenzo et al, 2018;Heller et al, 1986;Heller & Paola, 1989) At the latitude of the northern Utah, shortening occurred within the hinterland during the later Jurassic (Allmendinger & Jordan, 1984;Cruz-Uribe et al, 2015), while erosion occurred across the future Sevier belt and the Morrison Formation was deposited farther east ( Figure 17). The orogenic wedge front then propagated eastward onto the Willard thrust of the western Sevier belt.…”

Late Jurassic flare‐up of the Coast Mountains arc system, NW Canada, and dynamic linkages across the northern Cordilleran orogen

“…A west‐to‐east transect across the western United States (~38°N) spans the Franciscan Complex (accretionary wedge), Great Valley Group (forearc), Sierra Nevada batholith (continental arc), “Nevadaplano” Plateau (hinterland metamorphic belt), and Sevier thrust belt and adjacent basins (retroarc thrust belt and foreland basin system). A dynamic linkage between these Cordilleran elements is recorded by Late Jurassic deformation, metamorphism, and high‐volume magmatism (apparent intrusive rates of ~300 km 2 /Myr) in the Sierra Nevada arc system [ Wolf and Saleeby , ; Dunne and Walker , ; Wakabayashi and Dumitru , ; DeCelles et al ., ; Cao et al ., ; Saleeby and Dunne , ] that occurred during or after retroarc shortening and Barrovian metamorphism in the Luning‐Fencemaker and proto‐Sevier thrust belts to the east [ Schweickert and Lahren , ; Wyld et al ., ; DeCelles , ; Hoisch et al ., ; Cruz‐Uribe et al ., ].…”

Metamorphic record of collision and collapse in the Ediacaran‐Cambrian Araçuaí orogen, SE‐Brazil: Insights from P–T pseudosections and monazite dating

“…The data set was compiled for Theriak‐Domino by D. Tinkham. The analyses were investigated in the MnO‐NaO‐CaO‐K 2 O‐FeO‐MgO‐Al 2 O 3 ‐SiO 2 ‐H 2 O (MnNCKFMASH) system, which adequately describes the composition of the studied metapelites, provides results similar to naturally developed mineral assemblages, and covers most of the spectrum of pelitic compositions in greenschist and amphibolite facies series (Cruz‐Uribe, Hoisch, Wells, Vervoort, & Mazdab, ; Johnson, Brown, & Solar, ; Mahar et al., ; Tinkham, Zuluaga, & Stowell, ). Ti and Fe 3+ are not included in this model, and the biotite model assumes that the hydroxyl site is full.…”

“…Nonetheless, as garnet preserved growth zoning (profiles in Figure ), we use isopleths of spessartine ( X Sps ), almandine ( X Alm ) and/or grossular ( X Grs ) to constrain P–T field conditions and P–T evolution according to the procedures adopted by Cruz‐Uribe et al. (), Palin, Searle, Waters, Horstwood, and Parrish () and Staples, Gibson, Berman, Ryan, and Colpron (). Sample 146 is the only one that does not contain garnet.…”