کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4714878 1638466 2007 23 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Slab-tearing following ridge-trench collision: Evidence from Miocene volcanism in Baja California, México
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Slab-tearing following ridge-trench collision: Evidence from Miocene volcanism in Baja California, México
چکیده انگلیسی

Neogene magmatic activity in Central Baja California underwent a major change at ca. 12.5 Ma, when the Pacific–Farallon active oceanic ridge collided with the trench east of Vizcaíno Peninsula. The calc-alkaline magmatism which built the Comondú volcanic arc vanished and was replaced by unusual volcanic associations, which were erupted within six Late Miocene to Quaternary volcanic fields (Jaraguay, San Borja, San Ignacio, Santa Rosalía, Santa Clara, La Purísima), delineating a 600 km array along the Baja California Peninsula.New fieldwork, K–Ar datings and geochemical analyses on Jaraguay and San Borja lavas, combined with previous data, allow us to show that these associations include: (1) adakites emplaced between 12.5 and 8.2 Ma in the Santa Clara, Santa Rosalía and Jaraguay volcanic fields; (2) niobium-enriched basalts (NEB) in Santa Clara and Santa Rosalía (11.2 to 7.4 Ma); (3) tholeiitic basalts and basaltic andesites (11.3 to 7.2 Ma) displaying a very weak subduction imprint in La Purísima and San Ignacio; (4) alkali trachybasalts in Mesas San Carlos and Santa Catarina, northwest of Jaraguay (9.3 to 7.5 Ma), and finally (5) basalts and associated magnesian basaltic andesites and andesites. Locally referred to as “bajaites”, the latter lavas display very specific geochemical characteristics, including very high Sr and Ba contents. They were emplaced in all the above-mentioned volcanic fields between 14.6 and 5.3 Ma.The origin of these Late Miocene volcanics has been considered linked either to the opening of an asthenospheric window through which they ascended (tholeiites and alkali trachybasalts), or to the melting of its edges due to thermal erosion (adakites) and the subsequent reaction between adakitic melts and the supraslab mantle (NEB and “bajaites”). However, the identification of the remnants of the Pacific–Farallon fossil ridge south of Vizcaíno Peninsula indicates that active ridge subduction was not responsible for the opening of the asthenospheric window. We propose that the emplacement of slab window-related volcanic rocks between 13 and 7 Ma from ca. 25°N to 30°N, was due to a process of slab-tearing, which started when the active ridge collided with the trench east of Vizcaíno Peninsula. The oldest part of the downgoing plate sunk into the mantle, leading to the opening of a tear-in-the-slab, which likely started from the southern limit of the already existing Southern California slab window. It propagated parallel to the trench over about 600 km and developed into an asthenospheric window.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Volcanology and Geothermal Research - Volume 161, Issues 1–2, 1 March 2007, Pages 95–117
نویسندگان
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