Structures of the continental margin of Peru and Chile

Couch, Richard W.; Whitsett, Robert M.; Huehn, Bruce; Briceno-Guarupe, Luis

doi:10.1130/mem154-p703

Cited by 40 publications

(19 citation statements)

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“…By contrast, varying degrees of interaction with Precambrian basement (Arequipa Massif: Cobbing, 1985;Wasteneys et al, 1995) are indicated by Sr and Pb isotope data in the southern part of the Arequipa segment and in the Toquepala segment. These findings are in agreement with geophysical data showing the presence of a high-density (3 g/cm 3 ) structure within the upper crust below the western Peruvian trough in central Peru from Pisco to Trujillo, thus precluding the presence of a sialic basement in this area (Couch et al, 1981;Jones, 1981;Wilson, 1985). These facts have led to a debate on the tectonic setting of both the western Peruvian trough and the Peruvian Coastal batholith, with two main theories being proposed.…”

Section: Introductionsupporting

confidence: 76%

Geology, Geochronology, and Hf and Pb Isotope Data of the Raul-Condestable Iron Oxide-Copper-Gold Deposit, Central Coast of Peru

et al. 2006

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Raúl-Condestable is a >32 million metric ton (Mt) iron oxide-copper-gold (IOCG) deposit located on the Peruvian coast, 90 km south of Lima. The ore occurs as veins, replacement "mantos," and disseminations consisting of a chalcopyrite-pyrite-pyrrhotite-magnetite-amphibole mineral association. The geology of the studied area comprises a series of superposed volcanic edifices of Late Jurassic to Early Cretaceous age, which are part of a larger volcanic island to continental arc system. Particularly good exposures of the tilted host sequence allow the mapping of the Raúl-Condestable IOCG deposit in a nearly complete oblique cross section, from its associated volcanic edifice down to a paleodepth of about 6 km.U-Pb zircon ages indicate that in the deposit area felsic magmatic activity took place between 116.7 ± 0.4 and 114.5 ± 1 Ma, defining a new Raúl-Condestable superunit, the oldest so far, of the Peruvian Coastal batholith. This superunit is located west of the main part of the batholith and includes a dacite-andesite volcanic dome and a subvolcanic quartz-diorite porphyry sill-dike complex that were emplaced at 116.7 ± 0.4 and 116.4 ±0.3 Ma, respectively, followed by tonalite stocks and dikes emplaced between 115.1 ± 0.4 and 114.5 ± 1 Ma. All these rocks contain hornblende and/or biotite but no pyroxene and correspond to silica-and waterrich magmas following a calcic differentiation trend. Hf isotope data on zircons (εHf(115 Ma) = 5.2-7.5) and Pb isotope data on whole rock, combined with lithogeochemical results, suggest that magmas were generated by partial melting of the upper mantle, enriched through hydrous metasomatism and/or melting of subducted pelagic sediments. The lack of zircon inheritance suggests that there was no direct involvement of continental crust.The Raúl-Condestable IOCG deposit is connected in space and time with the magmatism of the Raúl-Condestable superunit. The mineralization was emplaced in the core of the dacite-andesite volcanic dome at a paleodepth of 2 to 3 km, surrounding two tonalitic intrusions formed at 115.1 ± 0.4 and 114.8 ± 0.4 Ma. The U-Pb age of hydrothermal titanite from IOCG veins at 115.2 ± 0.3 Ma indicates that the mineralization was coeval with (or more probably just followed) the emplacement of the tonalites. Re-Os geochronology on molybdenite did not yield reliable ages due to apparent Re loss. Copper ore is associated with a zoned alteration pattern, which surrounds the tonalite intrusions. It consists of a core of biotite alteration and quartz stockwork, †

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Section: Introductionsupporting

confidence: 76%

Geology, Geochronology, and Hf and Pb Isotope Data of the Raul-Condestable Iron Oxide-Copper-Gold Deposit, Central Coast of Peru

et al. 2006

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“…The mid-oceanic ridge passed beneath the Taitao Peninsula at 3 Ma and 6 Ma ago (Cande et al, 1987). In the northern part of the Chile margin triple junction, the slab is descending at an angle of 12°-30° (Couch et al, 1981;Bangs et al, 1992;Cahill and Isacks, 1985); the tip of the Taitao Peninsula is located <17 km landward from the trench axis, indicating that the top of the slab underlying this area at present is approximately 10 km deep at maximum.…”

Section: Geological Settingmentioning

confidence: 99%

Petrogenesis of the ridge subduction-related granitoids from the Taitao Peninsula, Chile Triple Junction Area

et al. 2013

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“…b Main lineaments and structures based on Landsat-5 TM image (Red Band 7; Green Band 4; Blue Band 2) interpretation, downloaded from http:// www.zulu.ssc.nasa.gov/mrsid/. c Geologic interpretation of the deep sturctures along the 9°S and 12°S gravimetric, crustal and subcrustal cross sections (Couch et al 1981;Jones 1981) of the continental margin of Peru 1989; Cobbing et al 1981). The extensional tectonic setting during which the Casma Group and related volcanosedimentary basins were formed was essentially attributed either to an extensional marginal basin with incipient formation of oceanic crust (e.g., Atherton and Aguirre 1992;Atherton 1990;Atherton and Webb 1989;Atherton et al 1985), or to the extensional tectonic (pull-apart?)…”

Section: Introductionmentioning

confidence: 99%

Formation of intra-arc volcanosedimentary basins in the western flank of the central Peruvian Andes during Late Cretaceous oblique subduction: field evidence and constraints from U?Pb ages and Hf isotopes

Polliand

Schaltegger

Frank

et al. 2005

Int J Earth Sci (Geol Rundsch)

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During late Early to Late Cretaceous, the Peruvian coastal margin underwent fast and oblique subduction and was characterized by important arc plutonism (the Peruvian Coastal Batholith) and formation of volcanosedimentary basins known as the Western Peruvian Trough (WPT). We present high-precision U-Pb ages and initial Hf isotopic compositions of zircon from conformable volcanic and crosscutting intrusive rocks within submarine volcanosedimentary strata of the WPT hosting the Perubar massive sulfide deposit. Zircons extracted from both the volcanic and intrusive rocks yield concordant U-Pb ages ranging from 67.89±0.18 Ma to 69.71±0.18 Ma, indicating that basin subsidence, submarine volcanism and plutonic activity occurred in close spatial and temporal relationship within the Andean magmatic arc during the Late Cretaceous. Field observations, satellite image interpretation, and plate reconstructions, suggest that dextral wrenching movements along crustal lineaments were related to oblique subduction. Wrench tectonics is therefore considered to be the trigger for the formation of the WPT as a series of pull-apart basins and for the emplacement of the Coastal Batholith. The zircon initial Hf values of the dated magmatic rocks fall between 5.5 and 7.4, and indicate only very subordinate influence of a sedimentary or continental component. The absence of inherited cores in the zircons suggest a complete lack of old basement below the WPT, in agreement with previous U-Pb and Sr isotopic data for batholithic rocks emplaced in the WPT area. This is supported by the presence of a most likely continuous block of dense ($3.0 g/cm 3 ) material observed beneath the WPT area on gravimetric crustal cross sections. We suggest that this gravimetric anomaly may correspond to a piece of lithospheric mantle and/or oceanic crust inherited from a possible Late Permian-Triassic rifting. Such young and mafic crust was the most probable source for arc magmatism in the WPT area.

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Structures of the continental margin of Peru and Chile

Cited by 40 publications

References 0 publications

Geology, Geochronology, and Hf and Pb Isotope Data of the Raul-Condestable Iron Oxide-Copper-Gold Deposit, Central Coast of Peru

Geology, Geochronology, and Hf and Pb Isotope Data of the Raul-Condestable Iron Oxide-Copper-Gold Deposit, Central Coast of Peru

Petrogenesis of the ridge subduction-related granitoids from the Taitao Peninsula, Chile Triple Junction Area

Formation of intra-arc volcanosedimentary basins in the western flank of the central Peruvian Andes during Late Cretaceous oblique subduction: field evidence and constraints from U?Pb ages and Hf isotopes

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