冈瓦纳西南部的三叠纪岩浆活动:退缩边缘的弧熔岩构造实例

IF 7.2 1区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Javiera González, Verónica Oliveros, Friedrich Lucassen, Christian Creixell, Felipe Coloma, Ricardo Velásquez, Laura Hernández, Paulina Vásquez, Simone A. Kasemann
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The Triassic magmatism in southwestern Gondwana: An example of arc batholith construction in a retreating margin
The Chollay-Piuquenes batholith (CPB) represents voluminous Lower-Middle Triassic magmatism on the western margin of Gondwana. It crops out in the Chilean Frontal Cordillera (28°30′S–30°30′S), covering ∼2,400 km2. It is composed of the Chollay and Piuquenes plutonic complexes, that were emplaced over a 16 Myr interval, with magma production rates ranging from 6 to 7.5 km3/Myr km−1. The batholith lithologies vary from diorites to syenogranites, with a predominance of monzogranites and granodiorites. It was previously interpreted as an anorogenic, post-collisional magmatism, originated from crustal anatexis in a rifting continental margin (Pre-Andean Cycle). This field and geochemical study proposes that CPB is likely a subduction-related batholith constructed in a convergent retreating margin. This interpretation is consistent with the Triassic geotectonic context proposed for western Gondwana. Moreover, the extensional context for the CPB emplacement is inferred from the contemporaneous development of forearc and back-arc basins, and from geochemical signals indicating Mesozoic crustal thinning along the margin. The CPB rocks exhibit subalkaline, meta- to peraluminous, calc-alkaline to alkaline-calcic affinities, enrichment in LILE relative to HFSE, depletion in Nb-Ta, Ti, Sr, and P, and Pb enrichment. The rocks display flat REE patterns (LaN/YbN: 3.40–13.78) and Al-in-Hbl barometer calculations (1.7–1.8 ± 0.6 kbar) suggest an epizonal emplacement. The Sr-Nd-Pb isotopic signature suggests a mixture of depleted mantle and continental crust, and not only crustal reworking, as the main magma-generating process. A comparative analysis of CPB samples with other well-known examples of both retreating and advancing margin batholiths allows the establishment of criteria to distinguish each tectonic context.
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来源期刊
Gondwana Research
Gondwana Research 地学-地球科学综合
CiteScore
12.90
自引率
6.60%
发文量
298
审稿时长
65 days
期刊介绍: Gondwana Research (GR) is an International Journal aimed to promote high quality research publications on all topics related to solid Earth, particularly with reference to the origin and evolution of continents, continental assemblies and their resources. GR is an "all earth science" journal with no restrictions on geological time, terrane or theme and covers a wide spectrum of topics in geosciences such as geology, geomorphology, palaeontology, structure, petrology, geochemistry, stable isotopes, geochronology, economic geology, exploration geology, engineering geology, geophysics, and environmental geology among other themes, and provides an appropriate forum to integrate studies from different disciplines and different terrains. In addition to regular articles and thematic issues, the journal invites high profile state-of-the-art reviews on thrust area topics for its column, ''GR FOCUS''. Focus articles include short biographies and photographs of the authors. Short articles (within ten printed pages) for rapid publication reporting important discoveries or innovative models of global interest will be considered under the category ''GR LETTERS''.
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