U-Pb systematics of monazite and xenotime: case studies from the Paleoproterozoic of the Grand Canyon, Arizona

Hawkins, D. P.; Bowring, Samuel A.

doi:10.1007/s004100050267

Cited by 151 publications

(71 citation statements)

References 35 publications

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“…A similar evolution has also been demonstrated in other metamorphic belts. Hawkins and Bowring (1999) showed that it took ca. 20 Ma for the Palaeoproterozoic migmatites of Grand Canyon to cool ca.…”

Section: Discussionmentioning

confidence: 99%

“…Thus the population of homogeneous zircon rims must obviously have formed by crystallization from leucosome melt or fluid, not resetting of previous zircons, which evidently remained unaffected. It should also be noted that the border of the core and rim is always sharp, which has been used as a strong argument against resetting by diffusion (Hawkins & Bowring, 1999). Thus the ages of the homogeneous zircons may be interpreted to represent a real crystallization age spectrum of new zircon, which most probably took place during the cooling and crystallization process of the leucosomes at ca.…”

Section: Metamorphic Evolution Of the Migmatitic Metapelitesmentioning

confidence: 99%

“…Recently, especially monazite data have proven useful in determining metamorphic and/or deformation phases (Bruguier et al, 1999;Crowley & Parrish, 1999, Foster et al, 2000, thermal history of metamorphic complexes (Aleinikoff et al, 2000;Hawkins & Bowring, 1999) or their geodynamic regime (Vavra & Schaltegger, 1999). One reason for the increased utility of monazite in geochronology of high-grade rocks is that monazite is apparently not reset and annealed as easily as earlier thought and may resist fluids even more efficiently than zircon (Parrish & Whitehouse, 1999;Schaltegger et al, 1999;Vavra & Schaltegger, 1999).…”

Section: Introductionmentioning

confidence: 99%

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Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

Tuisku¹,

Huhma²

2006

Bull Geol Soc Finland

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The migmatitic metapelites of the Lapland granulite belt (LGB) in the NE part of the Fennoscandian Shield represent an arc-related greywacke basin metamorphosed in the granulite facies. Detrital zircons from migmatitic metapelites are derived from 1.94 etrital zircons from migmatitic metapelites are derived from 1.94 zircons from migmatitic metapelites are derived from 1.94 derived from 1.94 − 2.9 Ga old acid source rocks (U-Pb SIMS ages). The clustering of detrital zircon ages between 1.97 and 2.2 Ga is problematic, because abundant felsic crust of this age is absent in the shield. The metasediments are characterized by Sm-Nd model ages of ca. 2.3 Ga. A younger, 1905 − 1880 Ma population of homogeneous zircons was formed during regional metamorphism. The peak high-grade metamorphism took place at ~1900 Ma and the latest chronological record from subsequent decompression and cooling phase is from ca. 1870 Ma. The norite-enderbite series of the LGB represents arc-magmas, which were intruded into the metasediments at ~1920 − 1905 Ma ago according to zircon U-Pb ages and were probably an important heat source for metamorphism. Older, zoned zircon grains in a quartz norite vein, initial ε Nd values of 0 to +1 and the continuous spectrum of LILE enrichment in the enderbite-series probably reflect assimilation of metasediments by magmas. Monazite U-Pb ages of migmatitic metasediments in the range 1906 − 1910 ± 3 Ma overlap the late stage of enderbite intrusion and growth of early metamorphic zircons. Garnetwhole rock Sm-Nd ages from leucosomes in the range 1880 − 1886 ± 7 Ma are concurrent with the growth of the youngest metamorphic zircons and probably indicate the crystallization of leucosomes or the influence of a fluid liberated from them. Isotopic and petrologic data reveal that the evolution of Lapland Granulite belt from the erosion of source rocks to the generation of a sedimentary basin, its burial, metamorphism and exhumation took place within ca. 60 Ma.

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Section: Discussionmentioning

confidence: 99%

Section: Metamorphic Evolution Of the Migmatitic Metapelitesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

Tuisku¹,

Huhma²

2006

Bull Geol Soc Finland

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“…However, many studies have shown that monazite ages are often not straightforwardly interpretable and even single grains may record complex isotopic histories (e.g. Parrish 1990;Hawkins and Bowring 1997;Crowley and Ghent 1999;Vavra and Schaltegger 1999;Zhu and O'Nions 1999;Simpson et al 2000). The growth of monazite during the course of amphibolite granulite eclogite facies prograde metamorphism is widely docu mented (see references above).…”

Section: Monazite Datamentioning

confidence: 99%

U-Pb evidence for a polyorogenic evolution of the HP-HT units of the NW Iberian Massif

Fernández‐Suárez

Corfú²,

Arenas

et al. 2002

Contributions to Mineralogy and Petrology

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A isotope dilution thermal ionisation mass spectrometry U Pb geochronological study was carried out on the high-pressure and high-temperature units (HP HT units) overlying the oceanic suture in the Allo chthonous Complexes of the NW Iberian Variscan Belt. The rocks investigated are seven granulite-to eclogite facies paragneisses and one leucosome within mafi c high pressure granulites in the Ordenes and Cabo Ortegal Complexes of NW Spain. U Pb dating of zircon, monazite, titanite and rutile reveal the presence of a pervasive Early Ordovician metamorphic event at ca. 500 480 Ma and a later Early Devonian event at ca. 400 380 Ma. The U Pb ages, in conjunction with petrological and structural data, indicate that the high-pressure event recorded by these rocks is Early Ordovician in age. Monazite ages in the paragneisses suggest that peak metamorphic conditions were reached at ca. 500 485 Ma. Subsequently, the rock ensemble underwent exhumation accompanied by partial melting and zircon growth at ca. 485 470 Ma. Melting of mafi c granulites was coeval with this latter episode as indicated by zircon crystallisation age in the leucosomes dated at ca. 486 Ma. Based on these data and on the general features of magmatism and metamorphic evolution, it is proposed that this process took place at a convergent plate boundary within a peri Gondwanan oceanic domain. Monazite, titanite and rutile data in some of the samples studied show evidence of a second metamorphic episode that took place between ca. 400 and 380 Ma (with a peak at ca. 390 385 Ma). This Early Devonian event, at variance with the previous one, was not pervasive, but, rather, was localised in areas of intense Variscan tectonothennal reworking. It is claimed that this later metamorphic event was recorded by the U Pb system in areas where monazite and titanite growth was enhanced by fluid circulation in highly strained rocks (Variscan shear zones). According to previous structural studies and Ar Ar dating of fabrics, this Early Devonian episode took place as the HP HT units were deformed and thrusted upon the ophiolitic units in the early stages of the Variscan collision.

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“…Microprobe geochronology also yields detailed information on sub-grain age domains based on the Th-U-Pb system (Williams et al 2007). TIMS analyses may involve whole single grains or sub-domains that can be obtained either mechanically by cutting/micro-drilling (Hawkins and Bowring 1997), or chemically using partial solution (Sato et al 2008a). …”

Section: Monazite U-pb Geochronologymentioning

confidence: 99%

Monazite ID-TIMS U-Pb geochronology in the LAGIR laboratory, Rio de Janeiro State University: protocols and first applications to the assembly of Gondwana supercontinent in SE-Brazil

Neto

Valeriano

Passarelli

et al. 2014

An. Acad. Bras. Ciênc.

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The chemical and spectrometric procedures of the U-Pb geochronology method on monazites, recently installed in the LAGIR laboratory, are described in detail. In addition, preliminary results on monazite samples from the Brasília and Ribeira belts are reported and discussed in the context of the regional geology. Several experiments for calibration of ion exchange chromatographic columns with the AG-1x8 resin, were performed with HCl, using dissolved natural monazite samples. The Pb blanks of reagents are ~0.5 pg/g in acids and ~1 pg/g in H 2 O. The total Pb blanks in chemical procedures were below 22 pg. Preliminary results are presented from three case studies related to Brasiliano orogenic belts of SE-Brazil, which correlate very well with previous age determinations from literature: two sub-concordant grains from an Araxá Group quartzite (southern Brasília belt) define a concordia age of 602.6 ±1.4 Ma; a -0.8% discordant grain from a quartzite of the São Fidelis Group (Costeiro Domain, central Ribeira belt) yielded a concordia age of 535.3 ± 2.4 Ma; two 0.4 % and 1.3 % discordant monazite grains from the post-collisional Itaoca Granite (Costeiro Domain, central Ribeira belt) define a concordia age of 476.4 ± 1.8 Ma.

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U-Pb systematics of monazite and xenotime: case studies from the Paleoproterozoic of the Grand Canyon, Arizona

Cited by 151 publications

References 35 publications

Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

Evolution of migmatitic granulite complexes: Implications from Lapland Granulite Belt, Part II: Isotopic dating

U-Pb evidence for a polyorogenic evolution of the HP-HT units of the NW Iberian Massif

Monazite ID-TIMS U-Pb geochronology in the LAGIR laboratory, Rio de Janeiro State University: protocols and first applications to the assembly of Gondwana supercontinent in SE-Brazil

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