Paleomagnetism of Permo–Triassic volcanic units in northern Patagonia: are we tracking the final stages of collision of Patagonia?

Luppo, Tomás; Dopico, Carmen I. Martínez; Rapalini, Augusto E.; Luchi, Mónica G. López de; Míguez, M.; Fanning, C. Mark

doi:10.1007/s00531-018-01672-9

Cited by 17 publications

(22 citation statements)

References 39 publications

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“…1a). Recently, Luppo et al (2019) found anomalous paleomagnetic pole positions for the 265-252 Ma volcanic rocks around La Esperanza, whereas the paleomagnetic poles of rhyolite dikes dated at 244 ± 2 Ma were consistent with the pole position for Middle-Triassic in most reference paths for South America.…”

Section: Introductionmentioning

confidence: 90%

“…All the pre-253 Ma magmatic units are crosscut by < 1 m thick, porphyritic to aphyric, dark grey mafic dikes (49-55% SiO 2 ; K 2 O < 2%; Fe 2 O 3t + MgO < 15%) which, in turn, are crosscut by acid microgranite dikes (Luppo et al, 2019). Mafic dikes with a preferred NE-SW trend (Fig.…”

Section: Andesitic Dikesmentioning

confidence: 99%

“…The first reliable time constraints for these rocks were established with WR Rb-Sr isochrons yielding late Permian to Middle Triassic ages (Pankhurst et al, 1992), superseding previous mistaken Carboniferous ages. U-Pb zircon crystallization ages were provided by Pankhurst et al (2006), and after by Martínez Dopico et al (2017b) and Luppo et al (2019). Together with thermochronological data (Martínez Dopico et al, 2013a,b;2017b), mica cooling ages bracketed the evolution of the rocks between mid-Permian (Kungurian-Roardian) and Middle Triassic (Anisian).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…1a). Permian to Triassic igneous rocks are distributed in an area of over 1000 km 2 (conservatively), although recent regional correlations (Luppo et al, 2018(Luppo et al, , 2019 suggest that the magmatic event could have extended over more than 3000 km 2 beneath large areas covered by the Cenozoic Somun Curá volcanic plateau.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…Apatite is abundant and appears either as stubby prisms when associated with amphibole or as acicular crystals in the groundmass. The unit is dated at 253 ± 2 Ma (U-Pb SHRIMP in zircon; Luppo et al, 2019). In the southernmost outcrops of the Collinao Dacite, a subvolcanic facies is exposed comprising a light grey equigranular felsic rock (74-77% SiO 2 ; K 2 O < 5%; 5 < MgO + Fe 2 O 3t < 2%), in which tourmaline aggregates are present.…”

Section: Collinao Dacitementioning

confidence: 99%

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Geochemistry and geochronology of the shallow-level La Esperanza magmatic system (Permian-Triassic), Northern Patagonia

Dopico

Luchi

Rapalini

et al. 2019

Journal of South American Earth Sciences

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The La Esperanza plutonic-volcanic complex is the largest Late Paleozoic-Early Triassic composite magmatic system of northern Patagonia. This paper reports new SHRIMP U-Pb zircon ages and K-Ar muscovite dating as well as whole-rock geochemical data for selected units. In addition, we present some new and reprocessed whole-rock Sr isotopic compositions. On the basis of the new and published data, three compositionally and isotopically distinct high-K magnesian calc-alkaline series were distinguished. Two of these are characterized by high Ba-Sr: (i) biotite and muscovite bearing rhyolites and granites (265 ± 2 Ma; 260 ± 2 Ma) and (ii) metaluminous amphibole-biotite bearing granodiorites (273 ± 2 Ma), monzogranites (255 ± 2 Ma), dacites (253 ± 2 Ma), and slightly peraluminous granites (dated herein as 251 ± 2 Ma). There is also a low Ba-Sr series of high-silica metaluminous rocks (granites and acid dike swarms; 250 ± 2 Ma and ≈244 ± 2 Ma). Geochemistry coupled with geochronology revealed a pulsatory multi-sourced open magmatic system with mafic magma replenishment and reactivation of crystal mushes that occurred before upward migration to upper crustal levels. Mafic magmas alternated with crust-derived magmas incrementally assembled in subvolcanic levels over 30 Ma. Zircon crystallization and mica cooling ages in the granite units allowed detection of two magmatic lulls, between 270 and 265 Ma and between 260 and 255 Ma. Both episodes coincide with a period of exhumation in upper crustal levels. The new temporal and geochemical constraints allow correlation of the La Esperanza plutonic-volcanic complex with the Los Menucos Group (258-248 Ma), encompassing a volume of magmatism comparable to a moderately sized large igneous silicic province. These mid-to-late Permian to Middle Triassic rocks record the transition between subduction-related magmatism (> 273 Ma) and post-orogenic extensional magmatism (< 250 Ma) in the Gondwana margin. Even though this magmatism would be coeval with the proposed collision of the Patagonia terrane, no expected syn-collisional magmatism or associated deformation were found in upper crustal levels. However, the different nature and melting conditions of the inferred sources of the magmas that crystallized before 270 Ma, between 265 and 260 Ma, and from 255 to 245 Ma, suggest that the La Esperanza plutonic-volcanic complex was assembled during a 30 Ma period of major plate reorganization.

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Section: Introductionmentioning

confidence: 90%

Section: Andesitic Dikesmentioning

confidence: 99%