Crustal structures of the Peru continental margin and adjacent Nazca plate, 9°S latitude

Jones, Paul Roy

doi:10.1130/mem154-p423

Cited by 36 publications

(28 citation statements)

References 21 publications

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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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“…During processing of the field data, the 24 channels were grouped into 12 channels (Kulm et al, 1981). An accom panying seismic-refraction transect was made that gave needed velocity control (Jones, 1981). From the refraction and gravity data, Jones (1981) concluded that the entire landward slope of the margin was composed of material accreted from the Nazca Plate, despite his observations that the material had a higher acoustic velocity and density than is normal for an accreted complex.…”

Section: Background and Scientific Objectivesmentioning

confidence: 99%

Site 683

1988

Proceedings of the Ocean Drilling Program

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Core recovery (%): 52.3 1 Suess, E., von Huene, R., et al., 1988. Proc. ODP, Init. Repts., 112 Principal results: Site 683 was chosen to investigate the history of verti cal tectonic movement of the Peruvian continental margin along the northern of two transects. Two objectives at this site were to recover metamorphic basement at a estimated depth of 600 mbsf and to ex tend the stratigraphy of industry wells Ballena and Delphin to the seaward flank of the Yaquina Basin. Extending the published ages assigned to sediments in these wells to Site 683 indicated a thin Neo gene sequence to a depth corresponding to 0.2 s two-way traveltime and underlain by dipping irregular reflectors of inferred Eocene age, extending from 0.2-0.5 s. The location appeared ideal for recovering samples of metamorphic basement unconformably overlain by sedi ment recording vertical tectonic movement. Drilling showed that these age assignments for the Yaquina Basin sediments were incorrect. The sequence recovered is mostly of Neo gene age, and fiie top of the basement reflections corresponds to middle Eocene mudstone. The hiatus that separates these stratigraphic units encompasses the upper Eocene, Oligocene, and lower Mio cene. These revised ages provide a history of events for the northern transect that is similar to the southern transect.The sedimentary sequence recovered at Site 683 consists of three units: (1) Quaternary-Pliocene diatomaceous mud with minor cal careous mud and turbidites, (2) poorly indurated middle Miocene di atomaceous mudstone and volcanic ash, and (3) well-indurated mid dle Eocene mudstone with minor volcanic ash, dolomite, and lime stone. The boundary between the upper and middle units is marked by a middle Pliocene to middle Miocene hiatus, and the boundary between the middle and lower units is the major biostratigraphic hia tus between middle Miocene and middle Eocene. Continuous hemi pelagic sedimentation was broken during the last 1 m.y. by numerous turbidites, with almost continuous volcanic activity peaking during the middle Miocene. Repeated cycles of upwelling-related sedimen tation, alternating with more terrigenous sedimentation, are recog-437 SITE 683 nizable in the upper part of the Quaternary. Moderate to extensive bioturbation throughout the section suggests that bottom waters re mained oxic. Structures within the sediments reveal a history of softsediment deformation related to downslope creep and slumping, fol lowed by extensional microfaulting and minor compressional microfaulting.The sediments at Site 683 show all of the early diagenetic pro cesses previously seen at Site 682; however, overall, the reactive zones are more readily discernable and reaction pathways less ambiguous. Gradients of dissolved chemical species are (1) steeper; (2) contain maxima and minima of calcium, magnesium, and alkalinity; (3) in dicate carbonate mineral diagenesis; (4) are more pronounced; and (5) indicate more abundant authigenic calcite and dolomite phases. The sulfate-reduction zone is compressed toward the sedim...

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“…Just to the east and beneath rocks of the Huarmey basin, seismic and gravity data show an arch-like structure of rock with a density of 3.0 g/cm 3 that was interpreted to be the result of crustal rupture and upwelling of mantle material into the crust (Jones 1981;Couch et al 1981).…”

Section: Other Considerationsmentioning

confidence: 99%

“…Seismic refraction, seismic reflection and gravity data collected in the northern sector at about 9ºS coupled with drill cores and outcrops on islands suggest that basement to the west of the Huarmey basin on the Outer Shelf High is composed of crystalline rocks cut by intrusions (Jones 1981;Thornburg and Kulm 1981;Couch et al 1981), now known to be part of the Arequipa block (Romero et al 2013). Just to the east and beneath rocks of the Huarmey basin, seismic and gravity data show an arch-like structure of rock with a density of 3.0 g/cm 3 that was interpreted to be the result of crustal rupture and upwelling of mantle material into the crust (Jones 1981;Couch et al 1981).…”

Section: Other Considerationsmentioning

confidence: 99%

Arc and Slab-Failure Magmatism in Cordilleran Batholiths I – The Cretaceous Coastal Batholith of Peru and its Role in South American Orogenesis and Hemispheric Subduction Flip

Hildebrand¹,

Whalen

2014

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We examined the temporal and spatial relations of rock units within the Western Cordillera of Peru where two Cretaceous basins, the Huarmey-Cañete and the West Peruvian Trough, were considered by previous workers to represent western and eastern parts respectively of the same marginal basin. The Huarmey-Cañete Trough, which sits on Mesoproterozoic basement of the Arequipa block, was filled with up to 9 km of Tithonian to Albian tholeiitic–calc-alkaline volcanic and volcaniclastic rocks. It shoaled to subaerial eastward. At 105–101 Ma the rocks were tightly folded and intruded during and just after the deformation by a suite of 103 ± 2 Ma mafic intrusions, and later in the interval 94–82 Ma by probable subduction-related plutons of the Coastal batholith. The West Peruvian Trough, which sits on Paleozoic metamorphic basement, comprised a west-facing siliciclastic-carbonate platform and adjacent basin filled with up to 5 km of sandstone, shale, marl and thinly bedded limestone deposited continuously throughout the Cretaceous. Rocks of the West Peruvian Trough were detached from their basement, folded and thrust eastward during the Late Cretaceous–Early Tertiary. Because the facies and facing directions of the two basins are incompatible, and their development and subjacent basements also distinct, the two basins could not have developed adjacent to one another. Based on thickness, composition and magmatic style, we interpret the magmatism of the Huarmey-Cañete Trough to represent a magmatic arc that shut down at about 105 Ma when the arc collided with an unknown terrane. We relate subsequent magmatism of the early 103 ± 2 Ma syntectonic mafic intrusions and dyke swarms to slab failure. The Huarmey-Cañete-Coastal batholithic block and its Mesoproterozoic basement remained offshore until 77 ± 5 Ma when it collided with, and was emplaced upon, the partially subducted western margin of South America to form the east-vergent Marañon fold–thrust belt. A major pulse of 73–62 Ma plutonism and dyke emplacement followed terminal collision and is interpreted to have been related to slab failure of the west-dipping South American lithosphere. Magmatism, 53 Ma and younger, followed terminal collision and was generated by eastward subduction of Pacific oceanic lithosphere beneath South America. Similar spatial and temporal relations exist over the length of both Americas and represent the terminal collision of an arc-bearing ribbon continent with the Americas during the Late Cretaceous–Early Tertiary Laramide event. It thus separated long-standing westward subduction from the younger period of eastward subduction characteristic of today. We speculate that the Cordilleran Ribbon Continent formed during the Mesozoic over a major zone of downwelling between Tuzo and Jason along the boundary of Panthalassic and Pacific oceanic plates.SOMMAIRENous avons étudié les relations spatiales et temporales des unités de roches dans la portion ouest de la Cordillère du Pérou, où deux bassins crétacés, la fosse d’accumulation de Huarmey-Cañete et la fosse d’accumulation péruvienne de l’ouest, ont été perçues par des auteurs précédents comme les portions ouest et est d’un même bassin de marge. La fosse de Huarmey-Cañete, qui repose sur le socle mésoprotérozoïque du bloc d’Arequipa, a été comblée par des couches de roches volcaniques tholéitiques – calco-alcalines de l’Albien au Thithonien atteignant 9 km d’épaisseur. Vers l’est, l’ensemble a fini par former des hauts fonds. Vers 105 à 101 Ma, les roches ont été plissées fortement puis recoupées par une suite d’intrusions vers 103 ± 2 Ma, durant et juste après la déformation, et plus tard dans l’intervalle 94 – 82 Ma, probablement par des plutons de subduction du batholite côtier. Quant à la fosse d’accumulation péruvienne de l’ouest, elle repose sur un socle métamorphique paléozoïque, et elle est constituée d’une plateforme silicoclastique – carbonate à pente ouest et d’un bassin contigu comblé par des grès, des schistes, des marnes et des calcaires finement laminés atteignant 5 km d’épaisseur et qui se sont déposés en continu durant tout le Crétacé. Les roches de la fosse d’accumulation péruvienne de l’ouest ont été décollées de leur socle, plissées et charriées vers l’est durant la fin du Crétacé et le début du Tertiaire. Parce que les facies et les profondeurs de sédimentation de ces deux fosses d’accumulation dont incompatibles, et que leur développement et leur socle sont différents, ces deux fosses ne peuvent pas s’être développées côte à côte. À cause de l’épaisseur accumulée, de sa composition et du style de son magmatisme, nous pensons que la fosse d’accumulation de Huarmey-Cañete représente un arc magmatique qui s’est éteinte vers 105 Ma, lorsque l’arc est entré en collision avec un terrane inconnu. Nous pensons que le magmatisme subséquent aux premières intrusions mafiques syntectoniques et aux réseaux de dykes de 103 ± 2 Ma sont à mettre au compte d’une rupture de plaque. Le bloc Huarmey-Cañete-batholitique côtier et son socle mésoprotérozoïque sont demeurés au large jusqu’à 77 ± 5 Ma, moment où il est entré en collision et a été poussé par-dessus la marge ouest sud-américaine partiellement subduite, pour ainsi former la zone de chevauchement de vergence est de Marañon. Nous croyons que la séquence majeure de plutonisme et d’intrusion de dykes qui a succédé à la collision finale à 73–62 Ma doit être reliée à une rupture de la plaque lithosphérique sud-américaine à pendage ouest. Le magmatisme de 53 Ma et plus récent qui a succédé à la collision finale, a été généré par la subduction vers l’est de la lithosphère océanique du Pacifique sous l’Amérique du Sud. Des relations temporelles et spatiales similaires qui existent tout le long des deux Amériques représentent la collision terminale d’un ruban continental d’arcs avec les Amériques durant la phase tectonique laramienne de la fin du Crétacé–début du Tertiaire. Elle a donc séparé la subduction vers l’ouest de longue date de la période de subduction vers l’est plus jeune caractérisant la situation actuelle. Nous considérons que le ruban continental de la Cordillère s’est constitué durant le Mésozoïque au-dessus d’une zone majeure de convection descendante entre Tuzo et Jason, le long de la limite entre les plaques océaniques Panthalassique et Pacifique.

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Crustal structures of the Peru continental margin and adjacent Nazca plate, 9°S latitude

Cited by 36 publications

References 21 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

Site 683

Arc and Slab-Failure Magmatism in Cordilleran Batholiths I – The Cretaceous Coastal Batholith of Peru and its Role in South American Orogenesis and Hemispheric Subduction Flip

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