The post-Paleozoic metallogenic evolution of southeastern Peru is clarified on the basis stratigraphic and lithologic settings majority known metallic ore deposits a regional program K-Ar 40 Ar- 39 Ar geochronology. This central Andean transect displays range mineralization types unparalleled in other regions country. Contrasting magmatic, tectonic, relationships are shown by calc-alkaline--shoshonitic Upper Triassic--Holocene Main Arc magmatic domain, underlying present Cordillera...

Isotopic age determinations ( 40 Ar/ 39 Ar) and associated magnetic polarity stratigraphy for Casamayoran fauna at Gran Barranca (Chubut, Argentina) indicate that the Barrancan “subage” of South American Land Mammal “Age” is late Eocene, 18 to 20 million years younger than hitherto supposed. Correlations radioisotopically dated with Cenozoic geomagnetic time scale faunal levels date within magnetochronologic interval from 35.34 36.62 megannums (Ma) or 35.69 37.60 Ma. This revision constrains...

Research Article| August 01, 2007 Queen Maud block: A newly recognized Paleoproterozoic (2.4–2.5 Ga) terrane in northwest Laurentia Michael E.J. Schultz; Schultz 1Department of Earth and Atmospheric Sciences, University Alberta, Edmonton, Alberta T6G 2E3, Canada Search for other works by this author on: GSW Google Scholar Thomas Chacko; Chacko Larry M. Heaman; Heaman Hamish A. Sandeman; Sandeman 2Northwest Territories Geoscience Office, Yellowknife, Northwest X1A 2R3, Antonio Simonetti;...

ABSTRACT The Salla beds of Bolivia contain a mammalian faunal assemblage assigned to the Deseadan South American Land Mammal "Age" (SALMA), known elsewhere principally in Patagonia. earliest platyrrhine monkey Branisella comes from single stratigraphie level these beds. age is debated; new radiometrie dates constrain SALMA and clarify timing first record platyrrhines America. oldest vertebrate fossils are contained within magnetic polarity interval ClOr, between 28.8 29.4 Ma. youngest occur...

The definition and characterization of the Oligocene-Miocene Crucero Supergroup southern Peru Inner Arc domain provide a previously unavailable lithostratigraphic framework for clarification geodynamic context magmatism across Peruvian transect. We integrate new lithostratigraphic, petrologic, 40Ar/39Ar geochronologic data these volcanic hypabyssal rocks with published information to establish geotectonic model transect since 55 Ma. early Eocene Early Miocene tectono-magmatic history region...

Abstract The Mistinibi-Raude block of the Core zone, southwestern Churchill Province (Quebec and Labrador), is a complex region Canadian Shield that consists several Neoarchean to early Paleoproterozoic intrusive complexes. This paper addresses new information from 2.55 Ga Nekuashu 2.32 Pelland intrusions in Quebec as well 2.57 Aucoin intrusion newly identified Mikuasheunipi Labrador. well-known Mesoproterozoic (1.24 Ga) Strange Lake pluton, host significant rare earth element (REE)...

The long-controversial age of the Lizard ophiolite is resolved by U-Pb dating three single magmatic zircons from a plagiogranite dyke near Porthkerris Point. This demonstrates that axial oceanic crust was undergoing extensional ductile shearing, mylonitization, amphibolite facies metamorphism and, probably, anatexis at 397 ± 2 (2σ) Ma. In conjunction with published K–Ar, 40 Ar– 39 Ar and Rb–Sr data for complex, this Early Devonian predicates protracted interval between intra-oceanic...

Research Article| September 01, 2001 Enriched Archean lithospheric mantle beneath western Churchill Province tapped during Paleoproterozoic orogenesis Brian L. Cousens; Cousens 1Ottawa-Carleton Geoscience Centre, Carleton University, Ottawa, Ontario K1S 5B6, Canada Search for other works by this author on: GSW Google Scholar Lawrence B. Aspler; Aspler 223 Newton Street, 2S6, Jeffrey R. Chiarenzelli; Chiarenzelli 3Department of Geology, State University New York at Potsdam, 13976, USA J....

Hudsonian tectonism in the western Churchill Province of Canada encompassed two periods granitic plutonism. The Hudson suite plutons represent xenocryst-rich, mainly monzogranitic, near-minimum melts emplaced near their source region thickened middle crust; Nueltin syenogranites and Pitz rhyolites were generated by intrusion basalt into extending crust. Zircons from four samples 20 analysed U–Pb SHRIMP techniques. Intrusion lasted ca. 50 million years, 1845 to 1795 Ma, with a peak around...

Integrated mapping, structural analysis, and U–Pb geochronology of the Committee Bay area, Nunavut, establish a record Neoarchean crustal growth followed by penetrative Paleoproterozoic deformation. Supracrustal rocks include lower ca. 2.73 Ga mafic–ultramafic volcanic-dominated sequence, middle, economically significant 2.71 intermediate volcanic-bearing sequence with intercalated sulphidized, gold-bearing iron formation, an upper <2.69 clastic ± komatiite–quartzite sequence. Following...

In this recent contribution, Nutman et al. (2001) provide the first SHRIMP U–Pb zircon age data for Lizard Peridotite and its immediate envelope, demonstrate usefulness of ion-microprobe geochronology in unravelling complex thermo-tectonic history inherent emplacement such assemblages plausibly oceanic rocks onto continental strata. Building on research Cook (2000), authors distinguish clearly between proper , a mass c. 15 kbar mantle tectonite, contiguous Crousa Downs gabbro, troctolite...

In situ U–Pb sensitive high-resolution ion microprobe (SHRIMP) analyses of monazite from upper amphibolite-facies paragneiss the Committee Bay supracrustal belt, central Rae domain, Canada, reveal three age populations: ca. 2350, 1850, and 1780 Ma. The 1850 Ma also corresponds to growth low Th/U zircon as indicated by SHRIMP separates melanosome leucosome. contextual advantage in analysis allows evaluation geochronological data terms regional structural metamorphic evolution. region is...

Results of 15 40 Ar/ 39 Ar age spectra for whole-rock argillite samples collected from within and adjacent to veins eight Meguma gold districts in the Terrane southern Nova Scotia are presented. The give excellent plateau ages (i.e., concordance plateaux, correlation, integrated ages) that range ca. 379 403 Ma, there is no apparent correlation with bulk rock composition (K 2 O, Al O 3 ) or sampling localities. In addition, a district similar analytical error, except one deposit, difference...