Origins of Textural, Compositional, and Isotopic Complexity in Monazite and Its Petrochronological Analysis

Hetherington, Callum J.; Backus, Ethan L.; McFarlane, Christopher R.M.; Fisher, Colleen; Pearson, D. Graham

doi:10.1002/9781119227250.ch3

Cited by 10 publications

(7 citation statements)

References 159 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This phase of tectonism was synchronous with peak metamorphic conditions, as it is defined in anorthosite-series rocks by garnet-absent pyroxene recrystallization (Spear and Markussen, 1997). All samples contain evidence for fluid-mediated recrystallization between 1060 and 980 Ma as evidenced by monazite and zircon textures and association of apatite along monazite rims (Harlov et al, 2008;Williams et al, 2011: Hetherington et al, 2018. These ages correspond with intrusion of the LMG (Valley et al, 2011;Chiarenzelli et al, 2017), post-kinematic corona growth in anorthositic rocks (Peck et al, 2018), megacrystic garnet formation (McLelland and Selleck, 2011), ubiquitous pegmatite injections (Lupulescu et al, 2012), and IOA mineralization within the leucogranites (Valley et al, 2011).…”

Section: ■ Discussion the Marcy Massif Detachment Zonementioning

confidence: 91%

Syn-collisional exhumation of hot middle crust in the Adirondack Mountains (New York, USA): Implications for extensional orogenesis in the southern Grenville province

et al. 2019

View full text Add to dashboard Cite

Extensional deformation in the lower to middle continental crust is increasingly recognized and shown to have significant impact on crustal architecture, magma emplacement, fluid flow, and ore deposits. Application of the concept of extensional strain to ancient orogenic systems, like the Grenville province of eastern North America, has helped decipher the structural evolution of these regions. The Marcy massif is a ∼3000 km2 Mesoproterozoic anorthosite batholith in the Adirondack Mountains (New York, USA) of the southern Grenville province. Bedrock geology mapping at 1:24,000 scale paired with characterization of bedrock exposed by recent landslides provides a glimpse into the structural architecture of the massif and its margin. New data demonstrate granulite- to amphibolite-facies deformational fabrics parallel the margin of the batholith, and that the Marcy massif is draped by a southeast-directed detachment zone. Within the massif, strain is localized into mutually offsetting conjugate shear zones with antithetic kinematic indicators. These relationships indicate that strain was coaxial within the Marcy massif, and that subsimple shear components of strain were partitioned along its margin. In situ U–Th–total Pb monazite analysis shows that deformation around and over the Marcy massif occurred from 1070 to 1060 Ma during granulite-facies metamorphism, and monazite from all samples record evidence for fluid-mediated dissolution reprecipitation from 1050 to 980 Ma. We interpret that rocks cooled isobarically after accretionary orogenesis and emplacement of the anorthosite-mangerite-charnockite-granite plutonic suite at ca. 1160–1140 Ma. Gravitational collapse during the Ottawan phase of the Grenville orogeny initiated along a southeast-directed detachment zone (Marcy massif detachment zone), which accommodated intrusion of the Lyon Mountain Granite Gneiss, and facilitated substantial fluid flow that catalyzed the formation of major ore deposits in the Adirondack Highlands.

show abstract

Section: ■ Discussion the Marcy Massif Detachment Zonementioning

confidence: 91%

Syn-collisional exhumation of hot middle crust in the Adirondack Mountains (New York, USA): Implications for extensional orogenesis in the southern Grenville province

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Analytical artefacts relate largely to inappropriate calibration of inter-element ratios because of matrix effects (Ireland, 1995), or to sample preparation. A bias from standard-sample matrix-mismatch (Fletcher et al, 2010;Hetherington et al, 2017;Stern and Berman, 2001) does not appear to be an issue here. Relevant instrumental indicators (UO + /U + , secondary tuning parameters) were very similar between standards and unknowns.…”

Section: Shrimp U-pb Monazite Datingmentioning

confidence: 83%

Mesoarchaean clockwise metamorphic P-T path from the Western Dharwar Craton

Dasgupta

Bhowmik

Dasgupta

et al. 2019

Lithos

View full text Add to dashboard Cite

In this study, we utilize high-alumina pelitic schist samples from the Holenarsipur Greenstone Belt, a component of the ca. 3.30-3.15 Ga Sargur Supergroup in the Western Dharwar Craton, South India to establish a Mesoarchaean metamorphic history in the terrane. On the basis of integrated textural, mineral compositional, metamorphic reaction history and P-T pseudosection modelling studies, garnet-monazite trace element thermometry and coupled monazite electron probe micro-analyzer and sensitive high-resolution ion microprobe U-Pb dating results, we constrain for the first time a Mesoarchaean metamorphism along a hairpin clockwise metamorphic P-T path in the Dharwar Craton. The path reveals a two-stage prograde segment with an initial phase of heating accompanying burial (dP/dT gradient~30 bar/°C) and a later phase of steep burial (ΔP 1.1 kbar, dP/dT gradient~110 bar/°C), peak metamorphism at 7.5 kbar, 640°C and a post-peak, steep decompression stage (P~6.3 kbar at 635°C). Chemically zoned monazite grains shielded within garnet or occurring in low-strain matrix domains were formed in two stages during the Mesoarchaean metamorphism: (a) Monazite cores with relatively lower Y concentrations, higher Th/U ratios, a strong negative Eu anomaly; their REE partitioning relationships with the garnet inner rim reveal their crystallization was synchronous with the growth of garnet. (b) Monazite rims with higher Y and uraniferous compositions and lower Th/U ratios which, combined with Y and HREE enrichments in the outer rim of garnet, indicate their formation during the post-peak decompression stage associated with coupled decompositions of garnet and zircon. We correlate U-Pb monazite core and rim ages at 3144 ± 7 Ma and 3105 ± 10 Ma respectively with the timings of peak and retrograde metamorphism. Our findings, when evaluated with the available geological, isotopic, geochronological data of Meso-to Palaeoarchaean extant and extinct felsic crust as well as thermo-mechanical models, predict the ca.3.14-3.11 Ga metamorphism in the Holenarsipur Greenstone Belt as part of a widespread tectono-thermal event in the Western Dharwar Craton. The event marks late stages of sagduction tectonics in the craton as it evolves from a predominantly vertical to a horizontal shortening mode.

show abstract

“…U-Pb isotope data were standardized using GSC-8153 monazite (a monazite sample provided by the Geological Survey of Canada; 507 Ma; [36]) and the accuracy of the results was confirmed using the 44069 monazite standard (424.9 ± 0.4 Ma [37]). The long-term reproducibility of the 44069 standard was assessed in [38] and analyses showed that expansion of 2σ errors to 1% on 207 Pb/ 235 U and 0.5% on 206 Pb/ 238 U were required to overlap the 'true' age of 424.9 ± 0.4 Ma [37] for 44069 monazite analyzed by TIMS and SHRIMP. The data related to the 44069 monazite standard are presented in the Supplementary Materials.…”

Section: Analytical Proceduresmentioning

confidence: 99%

U–Pb Geochronology of Hydrothermal Monazite from Uraniferous Greisen Veins Associated with the High Heat Production Mount Douglas Granite, New Brunswick, Canada

2019

Self Cite

View full text Add to dashboard Cite

A combination of in situ laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS) analyses guided by Scanning Electron Microscope-Back-Scattered Electron imaging (SEM-BSE) was applied to hydrothermal monazite from greisen veins of the Late Devonian, highly evolved, uraniferous Mount Douglas Granite, New Brunswick, Canada. Understanding the uraniferous nature of the suite and characterizing the hydrothermal system that produced the associated mineralized greisen veins were the main goals of this study. The uraniferous nature of the Mount Douglas Granite is evident from previous airborne radiometric surveys, whole-rock geochemical data indicating high U and Th (2-22 ppm U; 19-71 ppm Th), the presence of monazite, zircon, xenotime, thorite, bastnaesite, and uraninite within the pluton and the associated hydrothermal greisen veins, as well as anomalous levels of U and Th in wolframite, hematite, and martite within greisen veins. New U-Pb geochronology of hydrothermal monazite coexisting with sulfide and oxide minerals yielded mineralization ages ranging from 344 to 368 Ma, with most of them (90%) younger than the crystallization age of the pluton (368 ± 3 Ma). The younger mineralization age indicates post-magmatic hydrothermal activities within the Mount Douglas system that was responsible for the mineralization. The production of uraniferous greisen veins by this process is probably associated with the High Heat Production (HHP) nature of this pluton, resulting from the radioactive decay of U, Th, and K. This heat prolongs post-crystallization hydrothermal fluid circulation and promotes the generation of hydrothermal ore deposits that are younger than the pluton. Assuming a density of 2.61 g/cm 3 , the average weighted mean radiogenic heat production of the Mount Douglas granites is 5.9 µW/m 3 (14.1 HGU; Heat Generation Unit), in which it ranges from 2.2 µW/m 3 in the least evolved unit, Dmd1, up to 10.1 µW/m 3 in the most fractionated unit, Dmd3. They are all significantly higher than the average upper continental crust (1.65 µW/m 3 ). The high radiogenic heat production of the Mount Douglas Granite, accompanied by a high estimated heat flow of 70 mW/m 2 , supports the assignment of the granite to a 'hot crust' (>7 HGU) HHP granite and highlights its potential for geothermal energy exploration.

show abstract

Origins of Textural, Compositional, and Isotopic Complexity in Monazite and Its Petrochronological Analysis

Cited by 10 publications

References 159 publications

Syn-collisional exhumation of hot middle crust in the Adirondack Mountains (New York, USA): Implications for extensional orogenesis in the southern Grenville province

Syn-collisional exhumation of hot middle crust in the Adirondack Mountains (New York, USA): Implications for extensional orogenesis in the southern Grenville province

Mesoarchaean clockwise metamorphic P-T path from the Western Dharwar Craton

U–Pb Geochronology of Hydrothermal Monazite from Uraniferous Greisen Veins Associated with the High Heat Production Mount Douglas Granite, New Brunswick, Canada

Contact Info

Product

Resources

About