The generation of prograde P–T–t points and paths; a textural, compositional, and chronological study of metamorphic monazite

Foster, Gavin L.; Parrish, Randall R.; Horstwood, Matthew; Chenery, Simon; Pyle, Joseph M.; Gibson, H. Daniel

doi:10.1016/j.epsl.2004.09.024

Cited by 142 publications

(116 citation statements)

References 39 publications

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“…Buick et al, 2006;Gasser et al, 2012;Hermann and Rubatto, 2003), making it difficult to link the ages with the P -T conditions and crystallisation reactions of the phases. Emerging developments in linking 'age to stage', and particularly the use of combined petrography and traceelement data from major and accessory phases (petrochronology), allow high-spatial precision geochronological data to be more firmly linked to the P -T conditions of accessory phase crystallisation reactions (Foster et al, 2004;Gasser et al, 2012;Janots et al, 2008;Rubatto et al, 2013). This is achieved by detailed observation of textural relationships, geochemical analysis of coexisting accessory phases and systematic documentation of trace-element signatures in major phases that 'fingerprint' monazite-forming reactions (Foster et al, 2002(Foster et al, , 2000(Foster et al, , 2004Gasser et al, 2012;Hermann and Rubatto, 2003;Hoisch et al, 2008;Janots et al, 2006Janots et al, , 2007Janots et al, , 2008Janots et al, , 2009Kingsbury et al, 1993;Pyle and Spear, 2003;Rubatto et al, 2006;Smith and Barreiro, 1990;Spear, 2010;Wing et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Mottram

Warren

Regis

et al. 2014

Earth and Planetary Science Letters

141

139

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Editor: T.M. Harrison Keywords: inverted metamorphism ductile thrusting petrochronology monazite geochronologyIn the Himalayan region of Sikkim, the well-developed inverted metamorphic sequence of the Main Central Thrust (MCT) zone is folded, thus exposing several transects through the structure that reached similar metamorphic grades at different times. In-situ LA-ICP-MS U-Th-Pb monazite ages, linked to pressure-temperature conditions via trace-element reaction fingerprints, allow key aspects of the evolution of the thrust zone to be understood for the first time. The ages show that peak metamorphic conditions were reached earliest in the structurally highest part of the inverted metamorphic sequence, in the Greater Himalayan Sequence (GHS) in the hanging wall of the MCT. Monazite in this unit grew over a prolonged period between ∼37 and 16 Ma in the southerly leading-edge of the thrust zone and between ∼37 and 14.5 Ma in the northern rear-edge of the thrust zone, at peak metamorphic conditions of ∼790 • C and 10 kbar. Monazite ages in Lesser Himalayan Sequence (LHS) footwall rocks show that identical metamorphic conditions were reached ∼4-6 Ma apart along the ∼60 km separating samples along the MCT transport direction. Upper LHS footwall rocks reached peak metamorphic conditions of ∼655 • C and 9 kbar between ∼21 and 16 Ma in the more southerly-exposed transect and ∼14.5-12 Ma in the northern transect. Similarly, lower LHS footwall rocks reached peak metamorphic conditions of ∼580 • C and 8.5 kbar at ∼16 Ma in the south, and 9-10 Ma in the north. In the southern transect, the timing of partial melting in the GHS hanging wall (∼23-19.5 Ma) overlaps with the timing of prograde metamorphism (∼21 Ma) in the LHS footwall, confirming that the hanging wall may have provided the heat necessary for the metamorphism of the footwall. Overall, the data provide robust evidence for progressively downwards-penetrating deformation and accretion of original LHS footwall material to the GHS hanging wall over a period of ∼5 Ma. These processes appear to have occurred several times during the prolonged ductile evolution of the thrust. The preserved inverted metamorphic sequence therefore documents the formation of sequential 'paleothrusts' through time, cutting down from the original locus of MCT movement at the LHS-GHS protolith boundary and forming at successively lower pressure and temperature conditions. The petrochronologic methods applied here constrain a complex temporal and thermal deformation history, and demonstrate that inverted metamorphic sequences can preserve a rich record of the duration of progressive ductile thrusting.

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Section: Introductionmentioning

confidence: 99%

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Mottram

Warren

Regis

et al. 2014

Earth and Planetary Science Letters

141

139

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“…The findings have important implications in interpreting monazite and zircon ages from the granulites, in general, and the UHT granulites, in particular. In the last two decades, in situ electron microprobe (EMP), (Th þ U)-Pb monazite dating method (Suzuki and Adachi, 1991;Suzuki et al, 1994, Montel et al, 1996 has emerged as an important chronometer to date metamorphic events because of its ability to integrate textural, chemical and age information (Williams et al, 1999;Pyle and Spear, 2003;Kelsey et al, 2003bKelsey et al, , 2007Gibson et al, 2004;Goncalves et al, 2004;Kohn and Malloy, 2004;Foster et al, 2004;Kelly et al, 2006;McFarlane and Frost, 2009). Despite the limitations of the low precision of its ages (see Spear et al, 2009 for an updated review) and the lack of isotopic information to calculate the degree of discordance, if any, recent progress in analytical protocols of monazite analysis (Suzuki and Kato, 2008) makes it possible to generate quality REE, Y, Th, U and Pb data.…”

Section: Introductionmentioning

confidence: 99%

∼1.6 Ga ultrahigh‐temperature granulite metamorphism in the Central Indian Tectonic Zone: insights from metamorphic reaction history, geothermobarometry and monazite chemical ages

et al. 2011

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In this study, we present precise pressure-temperature (P-T) and age constraints of ultrahigh-temperature (UHT) metamorphism of the Bhandara-Balaghat granulite (BBG) domain at the southern margin of the Central Indian Tectonic Zone (CITZ). Supracrustal and metaigneous granulites of this domain, which lie as detached pods and lenses of various sizes within felsic gneiss-migmatite association record protracted high-T crustal anatexis events, broadly synchronous with and/or punctuated with felsic and mafic plutonism. Magnesian metagreywacke protolith of the supracrustal suite records extensive biotite melting and subsequent melt extractions at deep crustal, UHT metamorphic conditions (T ! $9008C at P$8 kbar), producing restitic mineral assemblages of garnet þ rutile, garnet þ cordierite and garnet þ aluminous orthopyroxene. The diversity of the mineral assemblages is related to the domainal-scale variation of the bulk rock composition. In situ chemical age dating of five monazite grains, which occur in the different textural settings of the garnet þ cordierite þ orthopyroxene þ rutile-bearing granulite reveals two age domains: (1) Pervasive $1.6 Ga domain, which is recorded in monazites occurring as inclusions in garnet and in the leucosome matrix is correlated with the timing of the UHT metamorphism. (2) $1.47 Ga domain reflects a fluid-mediated recrystallization event leading to dissolution and re-precipitation of older monazite. The $1.6 Ga monazite chemical ages provide robust constraints on the timing of the earliest stage of tectonothermal processes in the CITZ (defined here as the 'Central Indian Orogeny'). The significance of the $1.6 Ga hot orogenesis in interorogen correlation is discussed.

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“…Furthermore, as monazite crystallisation occurs at approximately P -T conditions near that of the staurolite isograd (Smith & Barreiro 1990), chemical ages can potentially be linked to the timing of metamorphic mineral growth, and a P -T -t path can be interpreted for the host rock (Foster et al 2000(Foster et al , 2002(Foster et al , 2004Foster & Parrish 2003;Fitzsimons et al 2005).…”

Section: Monazite Systematics and Age Determinationmentioning

confidence: 99%

Timing of Proterozoic metamorphism in the southern Curnamona Province: implications for tectonic models and continental reconstructions ∗

Rutherford

Hand

Barovich

2007

Australian Journal of Earth Sciences

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Chemical U -Th -Pb monazite ages from metasedimentary and meta-igneous units of the Willyama Supergroup have confirmed initial SHRIMP U -Pb metamorphic zircon ages constraining the onset of the earliest tectonometamorphic event (the Olarian Orogeny) at ca 1610 Ma in the southern Curnamona Province. An additional episode of high-grade metamorphism and heterogeneously distributed retrograde metamorphism and monazite recrystallisation occurred between ca 1570 and 1550 Ma. On the basis of monazite chemical U -Th -Pb ages from across the southern Curnamona Province, tectonometamorphic models based on ca 1690 Ma low-P, high-T metamorphism in the southern Curnamona Province are not supported. Furthermore, tectonic reconstructions that rely on the correlation of ca 1690 Ma deformation and metamorphism in the Broken Hill region with a similar aged event in the Mojave tarrane of southwestern Laurentia (AUSWUS) are not supported.

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The generation of prograde P–T–t points and paths; a textural, compositional, and chronological study of metamorphic monazite

Cited by 142 publications

References 39 publications

Developing an inverted Barrovian sequence; insights from monazite petrochronology

Developing an inverted Barrovian sequence; insights from monazite petrochronology

∼1.6 Ga ultrahigh‐temperature granulite metamorphism in the Central Indian Tectonic Zone: insights from metamorphic reaction history, geothermobarometry and monazite chemical ages

Timing of Proterozoic metamorphism in the southern Curnamona Province: implications for tectonic models and continental reconstructions ∗

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