Emplacement and temporal constraints of the Gondwanan intrusive complexes of northern Patagonia: La Esperanza plutono-volcanic case

Dopico, Carmen I. Martínez; Luchi, Mónica G. López de; Rapalini, Augusto E.; Wemmer, Klaus; Fanning, C. Mark; Basei, Miguel Ângelo Stipp

doi:10.1016/j.tecto.2017.05.015

Cited by 19 publications

(15 citation statements)

References 75 publications

(116 reference statements)

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“…The mineralogical composition of the enclaves is identical to that the host. The inequigranular monzogranite facies was dated as 255 ± 2 Ma using U-Pb SHRIMP methodology on magmatic zircons (Martínez Dopico et al, 2017a). This age agrees with K-Ar mica cooling ages and stratigraphic relations (Fig.…”

Section: La Esperanza Monzogranitesupporting

confidence: 77%

“…The granodiorite dated at 273 ± 2 Ma by Pankhurst et al (2006) belongs to this unit. The granodiorite bodies were emplaced as large horizontal layers in the border of the complex or as N-S aligned vertical feeders (magma conduits, see Martínez Dopico et al, 2017a). The Prieto Granodiorite is in fault contact with the Donosa Granite and is covered by younger volcanic and subvolcanic rocks to the east of Estancia La Esperanza.…”

Section: Prieto Granodioritementioning

confidence: 99%

“…Two granitoid facies with transitional contacts were recognised; the most extended facies is inequigranular, whereas the other encompasses porphyritic granites and crops out exclusively around puesto Calvo. The inequigranular facies crops out in the easternmost sector of La Esperanza as a subhorizontal layer or sill, whereas in the west, the spatial distribution of its outcrops reflects the NNW-SSE and NW-SE anisotropies of the basement (Martínez Dopico et al, 2017a). This facies comprises grey, variably ferromagnetic (10 −3 -10 −2 SI), inequigranular granodiorites and monzogranites (63-68% SiO 2 ; 3 < K 2 O < 4%; MgO < 2%; 0.90 < ASI < 1.13; 20 < La/Yb N < 30) in which euhedral plagioclase (or K-feldspar) is embedded in a matrix of granitic composition.…”

Section: La Esperanza Monzogranitementioning

confidence: 99%

“…This unit is the core of the complex. It crystallized at 260 ± 2 Ma (Martínez Dopico et al, 2017a) and comprises a pink euhedral K-feldspar megacrystic granite. Its discontinuous outcrops describe a large N-S elongated body with NW-SE and SW-NE, fault-related, rectilinear borders.…”

Section: Donosa Granitementioning

confidence: 99%

“…The aim of this paper is to present the magmatic stratigraphy, geochronological and geochemical backgrounds of a very well exposed example of a shallow composite magmatic system, the La Esperanza plutonic-volcanic complex of northern Patagonia (Llambías and Rapela, 1984;Martínez Dopico et al, 2013a,b;2017a), to provide a framework to test future hypotheses regarding the potential cogenetic evolution of the magmas. We report new SHRIMP U-Pb zircon data and two K-Ar muscovite dating as well as WR geochemical data for selected units.…”

Section: Introductionmentioning

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: La Esperanza Monzogranitesupporting

confidence: 77%

Section: Prieto Granodioritementioning

confidence: 99%

Section: La Esperanza Monzogranitementioning

confidence: 99%

Section: Donosa Granitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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