Successive reactivation of older structures under variable heat flow conditions evidenced by K–Ar fault gouge dating in Sierra de Ambato, northern Argentine broken foreland. (December 2015)

• Record Type: Journal Article
• Authors: Nóbile, Julieta C.; Collo, Gilda; Dávila, Federico M.; Martina, Federico; Wemmer, Klaus
• Is Part Of: Journal of South American earth sciences. Volume 64:Part 1(2015:Dec.)
• Page Start: 152
• Page End: 165
• Publication Date: 2015-12
• Subjects: Argentine broken foreland -- K–Ar dating -- Fault gouge dating -- Clay mineral geochronology; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2015.10.008
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: The Argentine broken foreland has been the subject of continuous research to determine the uplift and exhumation history of the region. High-elevation mountains are the result of N–S reverse faults that disrupted a W–E Miocene Andean foreland basin. In the Sierra de Ambato (northern Argentine broken foreland) the reverse faults offset Neogene sedimentary rocks (Aconquija Fm., ∼9 Ma) and affect the basement comprising Paleozoic metamorphic rocks that have been dated at ∼477−470 Ma. In order to establish a chronology of these faults affecting the previous continuous basin we date the formation age of clay minerals associated with fault gouge using the K–Ar dating technique. Clay mineral formation is a fundamental process in the evolution of faults under the brittle regime (<<300 °C). K–Ar ages (9 fractions from 3 samples collected along a transect in the Sierra de Ambato) vary from Late Devonian to Late Triassic (∼360–220 Ma). This age distribution can be explained by a long lasting brittle deformation history with a minimum age of ∼360 Ma and a last clay minerals forming event at ∼220 Ma. Moreover, given the progression of apparent ages decreasing from coarse to fine size fractions (∼360−311 Ma for 2−1 μm grain size fraction, ∼326−286 Ma for 1–0.2 μm and ∼291−219 Ma of <0.2 μm), we modeled discrete deformation events at ∼417 Ma (ending of the Famatinian cycle), ∼317–326 Ma (end of Gondwanic orogeny), and ∼194–279 Ma (Early Permian - Jurassic deformation). According to our data, the Neogene reactivation would not have affected the K–Ar system neither generated a significant clay minerals crystallization in the fault gouge, although an exhumation of more than 2 Km is recorded in this period from stratigraphic data. Graphical abstract: Highlights: Clay mineral formation within a fault zone was dated using K–Ar method. We established a chronology of faulting in Ambato range by modeling discrete deformation events. No Cenozoic ages were obtained. A depth-time modeling was used to explain the lack of Cenozoic ages with a low thermal regime.