U-Th-Pb Geochronology and Lu-Hf Isotope Geochemistry of Detrital Zircons in Metasedimentary Rocks of the Southern Coast Mountains Batholith

Dafov, Michelle Nikolay; Carrera, Anahi; Gehrels, George E.; Alberts, Dan; Pereira, Mekha; Cecil, M. Robinson; Rusmore, Margaret E.; Stowell, Harold H.; Woodsworth, G. J.

doi:10.2113/2020/8854686

Cited by 5 publications

(9 citation statements)

References 53 publications

(109 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sample 14RB01 did not produce a garnet Sm‐Nd age and we are therefore unable to construct a P–T–t path for this sample. However, detrital zircon analyses by Dafov et al (2020) identified possible 170–130 and 110‐ to 87‐Ma metamorphic zircon rim populations in the Bute and Knight Inlet. Dafov et al (2020) analysed a single sample from the same metasediment pendant as 14RB01, which contained 170‐ to 130‐Ma metamorphic zircon overgrowths (Dafov et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

“…The Insular superterrane consists of the Alexander and Wrangellia terranes (Monger et al, 1982). Dafov et al (2020) summarizes information on the terranes in the southern batholith. Previous metamorphic research has focused on the central CMB (Figure 1a) near Prince Rupert, where the CMB is broadly divided into the Central Gneiss Complex (CGC) and the Western Metamorphic Belt (WMB) (Crawford et al, 1987).…”

Section: Geologic Settingmentioning

confidence: 99%

“…While we cannot entirely rule out 110-to 87-Ma metamorphism of this sample, it is possible metamorphism occurred between 170 and 130 Ma and reached 4.9-7.4 kbar and 625-685 C (Figure 5d). Because we are unable to provide age constraints for the sample in this study (14RB01) and can only reference nearby detrital zircon samples (Dafov et al, 2020), we are reluctant to definitively relate this sample to a specific age range. Regardless if metamorphism of 14RB01 coincided with 170-130 or 110-87 Ma, metamorphism of metasediments in the Bute and Knight Inets is likely older than the majority of metamorphism to the west.…”

Section: Timing Conditions and Causes Of Metamorphismmentioning

confidence: 99%

“…Plutons in this region are mostly >102 Ma (Figure 1b; Rusmore et al, 2013; Cecil et al, 2018). Metasedimentary rocks include pelites, calc‐silicates, quartzites, and metabasites (Dafov et al, 2020). Metamorphism is primarily greenschist facies, with localized lower amphibolite facies.…”

Section: Introductionmentioning

confidence: 99%

“…Metamorphism is primarily greenschist facies, with localized lower amphibolite facies. Dafov et al (2020) identified 170‐ to 130‐ and 110‐ to 87‐Ma populations of metamorphic zircon in the metasediments from multiple pendants and inferred that metamorphism was related to heating from adjacent plutons during crustal thickening. Pelitic garnet‐bearing outcrops are sparse, and only one sample contained suitable mineralogy for this study (14RB01).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

The tempo and conditions of metamorphism during magmatism, southern Coast Mountains batholith, British Columbia, Canada

Bollen

Stowell

Rusmore

et al. 2021

Journal Metamorphic Geology

Self Cite

View full text Add to dashboard Cite

Garnet Sm‐Nd ages and pressure–temperature–time (P–T–t) paths for pelitic and semipelitic metamorphic rocks in the Mount Waddington area constrain the relationship between metamorphism and high‐flux magmatism recently identified in the southern Coast Mountains batholith. Amphibolite facies metamorphism in this area occurred at 99–90, 80, and 72–65 Ma at varying conditions of ~3 to 8 kbar and ~450°C to 685°C, partly associated with high magmatic fluxes at 85–70 and 61–48 Ma. P–T–t paths indicate increases in pressure and temperature of 2 kbar and 120°C at c. 80 Ma and up to 3 kbar and 165°C at 72–65 Ma. Garnet growth at c. 72 and 80 Ma was synchronous with a high‐flux event at 85–70 Ma. However, c. 65‐, 90‐, and 99‐Ma garnet growth cannot be directly attributed to nearby plutons and occurred during lulls between high magmatic flux events. The simplest explanation for the observed P–T–t paths for metamorphism is a single regional‐scale event between 99 and 64 Ma, synchronous with and in response to crustal contraction. Rock textures and pressure–temperature (P–T) isochemical phase diagrams indicate that most sampled rocks reached near‐solidus conditions with little or no melting. Although partial melting of sedimentary rocks has been proposed to contribute toward high‐flux magmatism in the northern and central Coast Mountains, the timing of metamorphism and high‐flux events differs in the Waddington area, suggesting that they are unrelated. Therefore, we conclude that metamorphism and partial melting of rocks exposed at the current level of exhumation played little or no role in construction of the batholith in the Waddington–Raleigh area of the southern Coast Mountains batholith.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

Section: Timing Conditions and Causes Of Metamorphismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

The tempo and conditions of metamorphism during magmatism, southern Coast Mountains batholith, British Columbia, Canada

Bollen

Stowell

Rusmore

et al. 2021

Journal Metamorphic Geology

Self Cite

View full text Add to dashboard Cite

show abstract

Modulation of Deformation by Magmatic Tempo, Coast Mountains Batholith, British Columbia, Canada

Rusmore,

Woodsworth,

Cecil

et al. 2024

Tectonics

View full text Add to dashboard Cite

The tectonomagmatic evolution of the southern Coast Mountains batholith, British Columbia reveals the relation of magmatic tempo, deformation, and relative plate motions which inform models for growth of continental crust and convergent plate dynamics. Magmatism in the southern batholith is episodic, derived primarily from the mantle, and reflects lower‐plate dynamics (Cecil et al., 2018, https://doi.org/10.1029/2018gc007874, 2021, https://doi.org/10.1130/ges02361.1). New field, structural, geochronologic, and geobarometric results from the southern batholith document three episodes of deformation, each spatially and temporally coincident with a high magmatic flux event (HFE). Sinistral faulting (<117–103 Ma) and penetrative deformation (110–90 Ma) occurred only within two distinct areas affected by a HFE at 114–102 Ma. Following a magmatic lull, crustal shortening occurred after 90 Ma and before 72 Ma within the region affected by a second HFE (85–70 Ma). After 70 Ma and before 53 Ma, >100 km of dextral slip occurred on the Coast shear zone and minor shortening affected 64–62 Ma plutons, overlapping with the 64–61 Ma HFE. Thus, at the crustal level exposed in the southern batholith, the timing and location of deformation is linked to magmatic tempo and the style of deformation varies through time. These results suggest that magmatic HFE modulate the timing and location of deformation while relative plate motions during HFE influence the style of deformation. Periods of deformation in batholiths may thus record high‐flux magmatic events and coeval plate motion but do not necessarily signal changes in plate motions.

show abstract

Linking the Gulf of Mexico and Coast Mountains batholith during late Paleocene time: Insights from Hf isotopes in detrital zircons

Pecha

Blum

Gehrels

et al. 2022

Tectonic Evolution of the Sevier-Laramide Hinterland, Thrust Belt, and Foreland, and Postorogenic Slab Rollback (180–20 Ma)

View full text Add to dashboard Cite

Paleocene Lower Wilcox Group sedimentation rates are three times the Cenozoic average for the Gulf of Mexico region and are attributed to Laramide tectonism within the Laramide–Rocky Mountains region. These increased rates likely represent the erosion of easily weathered Phanerozoic strata that blanketed the Laramide-age basement-cored uplifts. Geologic observations and U-Pb geochronology are not sufficient to fully address this hypothesis alone, so we conducted 439 Lu-Hf isotopic analyses on detrital zircons from eight samples from the San Juan Basin and five samples from the Gulf of Mexico Basin. Focusing on the zircons younger than 300 Ma allowed us to make direct comparisons to the eight principal components that comprise the North American Cordilleran magmatic arc: (1) Coast Mountains batholith; (2) North Cascades Range; (3) Idaho batholith; (4) Sierra Nevada batholith; (5) Laramide porphyry copper province; (6) Transverse Ranges; (7) Peninsular Ranges; and (8) Sierra Madre Occidental. The εHf(t) results range from +8.9 to –27.0 for the San Juan Basin samples and from +13.0 to –26.6 for the Gulf of Mexico samples. Using the San Juan Basin samples as a proxy for the eroded Mesozoic cover that was shed from the Laramide uplifts, we show that much of the sediment entering the Gulf of Mexico through the Houston and Mississippi embayments during the late Paleocene was derived from reworked cover from the greater Laramide–Rocky Mountains region. However, the Gulf of Mexico samples also include a distinct juvenile suite (εHf[t] ranging from +13 to +5) of zircons ranging in age from ca. 220 to 55 Ma that we traced to the Coast Mountains batholith in British Columbia, Canada. This transcontinental connection indicates an extension to the headwaters of the previously defined paleo-Mississippi drainage basin from ca. 58 to 56 Ma. Therefore, we propose a through-going fluvial system (referred to here as the “Coast Mountains River”) that was routed from the Coast Mountains batholith to the Gulf of Mexico. This expands the previously defined paleo-Mississippi drainage basin area by an estimated 280,000 km2. Our comprehensive Hf isotopic compilation of the North American Cordilleran magmatic arc also provides a benchmark εHf(t) versus U-Pb age plot, which can be used to determine provenance of detrital zircons (85–50 Ma) at the scale of specific region(s) within the Cordillera based on their εHf(t) values.

show abstract

U-Th-Pb Geochronology and Lu-Hf Isotope Geochemistry of Detrital Zircons in Metasedimentary Rocks of the Southern Coast Mountains Batholith

Cited by 5 publications

References 53 publications

The tempo and conditions of metamorphism during magmatism, southern Coast Mountains batholith, British Columbia, Canada

The tempo and conditions of metamorphism during magmatism, southern Coast Mountains batholith, British Columbia, Canada

Modulation of Deformation by Magmatic Tempo, Coast Mountains Batholith, British Columbia, Canada

Linking the Gulf of Mexico and Coast Mountains batholith during late Paleocene time: Insights from Hf isotopes in detrital zircons

Contact Info

Product

Resources

About