Campaign-style titanite U–Pb dating by laser-ablation ICP: Implications for crustal flow, phase transformations and titanite closure

Spencer, Khalil J.; Hacker, Bradley R.; Kylander-Clark, Andrew R.C.; Andersen, Torgeir B.; Cottle, John M.; Stearns, Michael A.; Poletti, Jacob; Seward, Gareth

doi:10.1016/j.chemgeo.2012.11.012

Cited by 218 publications

(225 citation statements)

References 66 publications

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“…The heavy mineral residues were mounted on microscope slides (Mange & Maurer, 1992) using Meltmount TM with a refraction of 1.66 and identified under the polarising microscope, with the relative abundances determined by grain counting. For that, the microscope slide was moved along linear traverses and all grains between two parallel lines were counted (i.e., ribbon counting; (Root et al, 2005;Spencer et al, 2013;Bradley R. Hacker, pers. comm., 2014;own field observations).…”

Section: Methodsmentioning

confidence: 99%

Heavy-mineral and garnet compositions of stream sediments and HP–UHP basement rocks from the Western Gneiss Region, SW Norway

Krippner¹,

Meinhold²,

Morton³

et al. 2016

NJG

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Section: Methodsmentioning

confidence: 99%

Heavy-mineral and garnet compositions of stream sediments and HP–UHP basement rocks from the Western Gneiss Region, SW Norway

Krippner¹,

Meinhold²,

Morton³

et al. 2016

NJG

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“…In the WGR they record chiefly Barrovian peak metamorphic conditions of~650-800°C and~1 GPa (Fig. 2) [Terry et al, 2000;Hacker et al, 2003;Labrousse et al, 2004;Walsh and Hacker, 2004;Root et al, 2005;Johnston et al, 2007a;Spencer et al, 2013;Fauconnier et al, 2014]. This was accompanied by partial melting that was locally extensive in the hinterland, but progressively more feeble toward the foreland [Ganzhorn et al, 2014] [Hacker et al, 2010 #5959] [ Kylander-Clark and Hacker, 2014].…”

Section: Geologic Settingmentioning

confidence: 99%

“…Like most well-exposed and extensively investigated UHP terranes, the WGR is dominated by quartzofeldspathic gneiss; eclogite and (U)HP peridotite comprise only a few volume percent of the Region. The quartzofeldspathic gneiss and eclogite protoliths formed chiefly by magmatism at~1.68-1.64 Ga, 1.29-1.24 Ga, and~990-950 Ma [Corfu and Andersen, 2002;Walsh et al, 2007;Krogh et al, 2011;Corfu et al, 2013]; regional metamorphism [Roffeis and Corfu, 2014] associated with the~1.0-0.9 Ga magmatism reached temperatures of~775-825°C [Spencer et al, 2013]. During the Caledonian orogeny, subductionrelated magmatism related to closure of the Iapetus ocean ended at 430 Ma [Corfu et al, 2006], marginal basin ophiolites and island arcs were emplaced onto the Baltica craton in the Wenlock [Andersen et al, 1990], and the previously hyperextended continental margin [Andersen et al, 2012] began to contract.…”

Section: Geologic Settingmentioning

confidence: 99%

“…2) in the core of the orogen [see geothermometry reported below and summaries in Cuthbert et al, 2000;Ravna and Terry, 2004;Hacker, 2006;Spencer et al, 2013]. Ultrahigh-pressure (UHP) rocks with coesite, diamond, or equivalent metamorphic pressures [e.g., Smith, 1984;Vrijmoed et al, 2008] are restricted to three main domains in the hinterland (pink in Fig.…”

Section: Geologic Settingmentioning

confidence: 99%

“…In the eastern part of the WGC, metamorphic titanite and garnet are Proterozoic, whereas in the western part titanite and garnet at most locations are Caledonian [Johnston et al, 2007b;Peterman et al, 2009;Spencer et al, 2013] (Fig. 1) Walsh et al, 2007;Young et al, 2011;Walsh et al, 2013]; these are inferred to record westward-propagating exhumation of the Western Gneiss Region [Walsh et al, 2013].…”

mentioning

confidence: 99%

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Monazite response to ultrahigh-pressure subduction from U–Pb dating by laser ablation split stream

et al. 2015

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To assess the response of monazite during subduction of continental crust to mantle depths, U-Pb isotopic ratios and elemental abundances were measured simultaneously by laser-ablation split-stream inductively-coupled plasma mass spectrometry (LASS) in rocks from the ultrahigh-pressure Western Gneiss Region of the Scandinavian Caledonides. Nearly seventy different samples of quartzofeldspathic basement and overlying metasedimentary rocks were studied. Pre-subduction monazite (chiefly 1.6 Ga and 1.0 Ga) is preserved locally in the structurally lowest, basement rocks because earlier, Precambrian tectonism produced coarse-grained, high-grade rocks that were resistant to further recrystallization in spite of syn-subduction temperatures and pressures of 650-800°C and 2-3.5 GPa. A few of the monazite in the metasedimentary rocks atop the basement preserve syn-subduction U-Pb dates, but the majority continued to recrystallize during post-subduction exhumation and record a general westward decrease in age related to westward-progressing exhumation. The absence of Precambrian monazite in the metasedimentary rock atop the basement suggests that sedimentation postdated the 1.0-0.9 Ga high-grade metamorphism and was late Proterozoic to early Paleozoic.

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Age and significance of felsic dikes from the UHP western gneiss region

Kylander‐Clark

Hacker

2014

Tectonics

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Twenty-one plagioclase-bearing dikes were analyzed to place firmer limits on the end of (ultra)high-pressure (UHP) metamorphism across the Western Gneiss Region (WGR). Nineteen dikes were analyzed with laser ablation split-stream petrochronology to tie the U-Pb dates to zircon rare earth element (REE) chemistry, and a few key samples were analyzed by chemical abrasion thermal ionization mass spectrometry to provide high-precision constraints. All analyzed dikes yielded zircons with REE chemistry consistent with low-pressure crystallization. Approximately half of the dikes yield Precambrian dates; nondeformed dikes of this age support previous interpretations that much of the WGR underwent limited deformation during Caledonian subduction and exhumation. The oldest Caledonian dikes have dates that overlap with the circa 420-400 Ma eclogite dates from the region; this discrepancy indicates that either (1) cryptic structures separate early exhumed material from later exhumed material, (2) some of the dike dates are not low-pressure crystallization ages, or (3) post-406 Ma dates from eclogites are posteclogite-facies retrogression ages.

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Campaign-style titanite U–Pb dating by laser-ablation ICP: Implications for crustal flow, phase transformations and titanite closure

Cited by 218 publications

References 66 publications

Heavy-mineral and garnet compositions of stream sediments and HP–UHP basement rocks from the Western Gneiss Region, SW Norway

Heavy-mineral and garnet compositions of stream sediments and HP–UHP basement rocks from the Western Gneiss Region, SW Norway

Monazite response to ultrahigh-pressure subduction from U–Pb dating by laser ablation split stream

Age and significance of felsic dikes from the UHP western gneiss region

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