Sm?Nd dating of multiple garnet growth events in an arc-continent collision zone, northwestern U.S. Cordillera

Getty, Stephen R.; Selverstone, Jane; Wernicke, Brian P.; Jacobsen, S. B.; Aliberti, Elaine A.; Lux, Daniel R.

doi:10.1007/bf00712977

Cited by 73 publications

(74 citation statements)

References 25 publications

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“…As already observed in other studies (Getty et al 1993, Rehkamper et al 1996 and Sato 1998), we had successful attacks using Savilex capsules. Some samples, however, such as garnet-rich rocks and some ultramaphic rocks were not entirely dissolved and needed to be transferred to bombs.…”

Section: Extraction Of Sm and Nd Of Rock Samplessupporting

confidence: 83%

The Sm-Nd isotopic method in the geochronology laboratory of the University of Brasília

Gioia

Pimentel

2000

An. Acad. Bras. Ciênc.

270

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Nd isotopes represent one of the best tools to investigate the processes involved in the evolution of the continental crust and mantle. This is due mainly to the similar geochemical behaviour of Sm and Nd, both light rare earth elements, which inhibits their fractionation during most varied geological processes. In order to carry out crustal evolution studies in central Brazil, the Sm-Nd isotopic method was implanted at the Geochronology Laboratory of the University of Brasília. The Sm-Nd separation methodology is basically that described in Richard et al. (1976), with the addition of some improvements. In this study we describe in detail the methodology used in Brasília. Precision and accuracy were checked with the international standards such as JB-3, BCR-1, BHVO-1 and La Jolla, and the following results were found: JB-3 (Nd=15.74 ppm and Sm=4.28 ppm), BCR-1 ( 143 Nd/ 144 Nd=0.512647±8, Nd=28.73 ppm and Sm=6.66 ppm), BHVO-1 (Nd=24.83 ppm and Sm=6.2 ppm) and La Jolla ( 143 Nd/ 144 Nd=0.511835±14).

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Section: Extraction Of Sm and Nd Of Rock Samplessupporting

confidence: 83%

The Sm-Nd isotopic method in the geochronology laboratory of the University of Brasília

Gioia

Pimentel

2000

An. Acad. Bras. Ciênc.

270

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“…Garnet whole-rock Sm-Nd ages from tectonized amphibolite ∼25 km southwest of Riggins suggest collision of the Wallowa terrane with western Laurentia prior to 128 ± 3 Ma (Getty et al 1993; sample locality 598, Fig. 2).…”

Section: Jura-cretaceous Tectonismmentioning

confidence: 96%

“…40 Ar/ 39 Ar localities (R, D) and plateau ages of Snee et al (1995): R7-hbl, 117 ± 0.6 Ma; R11-hbl, 84.9 ± 0.3 Ma; R12-bio, 82.6 ± 0.4 Ma; R17-hbl, 106.8 ± 0.5 Ma; R30-hbl, 118.1 ± 0.6 Ma; D81-1-hbl, 145.1 ± 1.5 Ma. 147 Sm/ 144 Nd garnet localities of Getty et al (1993) are shown for single-stage (598, 128 ± 3 Ma) and two-stage (422, pre-144 Ma) growth. 147 Sm/ 144 Nd garnet localities 48 (112.5 ± 1.5 Ma) and 7a (113 ± 35 Ma) provided from McKay (2011).…”

Section: Structures Of the Riggins Regionmentioning

confidence: 99%

Age and structure of the Crevice pluton: overlapping orogens in west-central Idaho?

et al. 2012

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New U-Pb zircon geochronology from the Riggins region of west-central Idaho refines the timing of contractional deformation across the Salmon River suture zone (SRSZ), a broad north-to northeast-striking belt (>25 km wide) of high strain recording Jura-Cretaceous island-arc-continent collision. Laser ablation -inductively coupled plasma -mass spectrometry (LA-ICP-MS) yields mid-Cretaceous crystallization ages on formerly undated plutonic rocks sampled from the Salmon River canyon. In the Crevice pluton (∼105 Ma), the development of steep to moderate northerly striking gneissic foliation (S1) was followed by tops-to-the-west slip on shallow mylonitic shear zones (S2) and brittle overprinting via systematic joints (Jn) of regional extent. Together, these structures form the pluton's internal architecture. Subvertical gneissic foliation in the adjacent Looking Glass pluton (∼92 Ma) indicates ductile deformation was ongoing in the Late Cretaceous. Prior to this investigation, penetrative fabrics in local arc volcanogenic, plutonic, and continental rocks have been unequivocally linked to post-collisional dextral transpression on the narrow (<10 km wide) western Idaho shear zone (WISZ). As an alternative to this model which requires spatially overlapping but temporally distinct orogenic belts (WISZ-SRSZ), we consider a protracted history whereby regional synmetamorphic structures accumulated over a pre-118 Ma to post-92 Ma interval without an overprinting orogen-scale ductile shear zone. In our view, a progressive deformation history more accurately accounts for the time-transgressive nature and structural continuity of fabrics observed across the arc-continent transition. This tectonic history proposed for western Idaho may be analogous to other long-lived accretionary margins in the North American Cordillera (e.g., Omineca Belt of southeastern British Columbia).Résumé : Une nouvelle géochronologie par U-Pb sur zircon pour la région Riggins du centre-ouest de l'Idaho précise le moment de la déformation par contraction à travers la zone de suture de Salmon River (SRSZ), une large ceinture (>25 km) de direction nord à nord-est de grandes contraintes enregistrant des collisions au Jurassique-Crétacé entre des îles d'arcs et le continent. La spectrométrie de masse à source plasma à couplage inductif avec ablation laser (LA-ICP-MS) a donné des âges de cristallisation au Crétacé moyen à partir de roches plutoniques prélevées dans le canyon de la rivière Salmon non datées antérieurement. Dans le pluton Crevice (∼105 Ma), le développement de foliation gneissique (S1) à direction nord et à pendage fort à modéré a été suivi par un décrochement « sommet vers l'ouest » sur des zones de cisaillement mylonitiques à faible profondeur (S2) et une surimpression cassante par des joints (Jn) systématiques d'étendue régionale. Ensemble, ces structures forment l'architecture interne du pluton. Une foliation subverticale des gneiss dans le pluton adjacent de Looking Glass (∼92 Ma) indique qu'une déformation ductile était en cours au Crétac...

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“…For the rocks of multi-metamorphism, there are many successful examples of revealing the retention of Sm-Nd isotopic memory of early metamorphism in garnet [11][12][13][14] . The typical one is from Hensen and Zhou [14] on the Pan African granulite terrain in southeast Antarctic.…”

Section: Discussionmentioning

confidence: 99%

“…That made the garnet Sm-Nd method capable of dating metamorphic age. Particular advances are in age determination of multi-metamorphism [11][12][13][14] .In this note, we apply garnet+whole rock Sm-Nd isochron to determine the age of the HP metamorphism. A whole rock isochron of HP granulites is also measured.…”

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confidence: 99%

Sm-Nd age dating of high-pressure granulites and amphibolite from Sanggan area, North China craton

Guo

Zhai

2001

Chin.Sci.Bull.

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The high pressure (HP) metamorphic age has been dated to HP rocks from the Sanggan area, North China craton. We have got garnet+whole rock isochron ages of (1 842±38) Ma for HP granulite, and (1 856 ± 26) Ma for HP amphibolite. The Sm-Nd whole rock isochron of HP granulites give out an age of (1 870±150) Ma with Nd depleted mantle model age of (2 402-2 482) Ma. Considering the Nd isotope homogenization during the peak metamorphism of the HP granulite, Sm-Nd closure temperature and the retention of Nd isotopic memory in garnets partially broken down during decompression, all these isochron ages are thought to be HP metamorphic age. Furthermore, we proposed that the HP metamorphism took place at the end of Paleoproterozoic during the large-scale collision and assembly of the North China craton.In recent years, most high pressure (HP) metamorphic rocks have been recognized from the Hengshan Mt. to Chicheng in the Sanggan area, North China craton [1,2] . The major rock types are HP basic granulites, amphibolites and retrograde eclogites. The HP granulites subjected to HP metamorphism at about 1.3-1.6 GPa and 800-850℃. All the HP rocks have a clockwise PT path with rapid isothermal decompression [3][4][5] . They are most probably the products of collisional orogen. However, it has not yet been determined when the significant Precambrian collisional orogenic event occurred.In general, Sm-Nd isochron of garnet+whole rock± other minerals is supposed to produce metamorphic age determination. These years, more understanding to Sm-Nd system in garnet has been achieved, especially about how the closure temperature is affected by garnet radius, initial temperature and cooling rate [6][7][8][9][10] . That made the garnet Sm-Nd method capable of dating metamorphic age. Particular advances are in age determination of multi-metamorphism [11][12][13][14] .In this note, we apply garnet+whole rock Sm-Nd isochron to determine the age of the HP metamorphism. A whole rock isochron of HP granulites is also measured. Then, the most possible age of HP metamorphism will be discussed, which will define the age of the collisional orogeny and assembly of the North China craton. Geological background and petrology of the HP metamorphic rocksThe major HP metamorphic rocks in the North China craton are HP basic granulite, HP amphibolite and retrograde eclogite [4,5,15] . In the Sanggan area, plenty of HP rocks were distributed northeast from the Hengshan Mt. to Chicheng as lenticular blocks or enclaves in highly deformed TTG gneiss, granitic gneiss, migmatite and granite. Therefore, the occurrences of HP rocks define the Sanggan strucure zone ( fig. 1). The samples of HP granulites and amphibolite of this note are from Xiwangshan and Womakeng respectively. These HP metamorphic rocks have been carefully investigated petrologically [3,16,17] , which will make the samples typical and representative. Fig. 1. Sketch map of Precambrian geology in the Sanggan area, North China craton.The HP granulites contain abundant garnet porphyroblasts, in which mi...

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Sm?Nd dating of multiple garnet growth events in an arc-continent collision zone, northwestern U.S. Cordillera

Cited by 73 publications

References 25 publications

The Sm-Nd isotopic method in the geochronology laboratory of the University of Brasília

The Sm-Nd isotopic method in the geochronology laboratory of the University of Brasília

Age and structure of the Crevice pluton: overlapping orogens in west-central Idaho?

Sm-Nd age dating of high-pressure granulites and amphibolite from Sanggan area, North China craton

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