Detrital zircon (U‐Th)/(He‐Pb) double‐dating constraints on provenance and foreland basin evolution of the Ainsa Basin, south‐central Pyrenees, Spain

Abstract

South central Pyrenean foreland basin fill preserves the eroded remnants of the early stages of fold‐thrust belt evolution and topographic growth. Specifically, the Eocene Hecho Group in the Ainsa Basin contains a succession of turbiditic channels and levees deposited in the transition zone between the fluvial‐deltaic and deep marine depozones. Detailed isotopic provenance analyses allow for the reconstruction of sediment sources of the ancient sediment routing systems. This study presents 2332 new detrital zircon (DZ) U‐Pb ages and 246 new DZ double‐dated (U‐Th)/(He‐Pb) ages from 19 turbiditic and fluvio‐deltatic sandstones in the Ainsa Basin. These data indicate a progressive provenance shift from Cadomian/Caledonian plutonic and metamorphic rocks of the eastern Pyrenees to Variscan plutonic rocks in the central Pyrenees. Minor sediment contributions from sources located to the S and SE of the basin are seen throughout the section. New DZ (U‐Th)/He results identify four main cooling events: Pyrenean orogenesis (~56 Ma), initial basin inversion (~80 Ma), Cretaceous rifting (~100 Ma), and pre‐Mesozoic cooling ages related to earlier tectonic phases. This study imposes new constraints on the paleogeographic evolution of the Pyrenees and illustrates that high‐frequency fluctuations in sediment delivery processes and sediment routing introduce superimposed noise upon the basin‐scale long‐term provenance evolution during orogenesis.

Thermochronological Evidence of Early Orogenesis, Eastern Pyrenees, France

“…We interpret this cooling signature as due to denudation of the Agly‐Salvezines block at the beginning of the main Eocene phase of orogenesis. Exhumation‐related cooling is observed over the whole Pyrenees, propagating southward from the North Pyrenean basement massifs into the Axial Zone from the early Eocene to the late Oligocene (Bosch et al, ; Hart et al, ; Labaume et al, ; Mouthereau et al, , and references therein; Rushlow et al, ; Thomson et al, ; Vacherat et al, , ).…”

“…Extensive low‐temperature thermochronology studies in the Pyrenees over the last 20 years have produced a world‐class data set to constrain crustal thermal behavior during orogenesis (Bosch et al, ; Hart et al, ; Labaume et al, ; Mouthereau et al, , and references therein; Rushlow et al, ; Thomson et al, ; Vacherat et al, , ). Bedrock low‐temperature thermochronology (AHe and apatite fission track [AFT]) data from the Axial Zone and the basement massifs in the central North Pyrenean Zone record only the Eocene–Oligocene (50–20 Ma) main collision cooling history, younging from east to west and from north to south (Mouthereau et al, ; Whitchurch et al, ).…”

Innovations in (U–Th)/He, Fission Track, and Trapped Charge Thermochronometry with Applications to Earthquakes, Weathering, Surface‐Mantle Connections, and the Growth and Decay of Mountains

“…FT and (U–Th)/He data can be acquired on crystals previously analyzed for U–Pb geochronology, aided by analytical advances of laser ablation and noble gas mass spectrometry analyses. This approach includes “double” U–Pb and FT or He analysis of apatite or zircon (Campbell et al, ; Carter & Moss, ; Fosdick et al, ; Lease, Haeussler, & O'Sullivan, ; Odlum & Stockli, ; Rahl et al, ; Reiners et al, ; Ternois et al, ; Thomson et al, ) or U–Pb, FT, and (U–Th)/He “triple” dating (e.g., Carrapa et al, ; Danišík, ; Danišík et al, ). Integration of data from two or more thermochronometric systems with different temperature sensitivities in the same mineral permits a more detailed reconstruction of the thermal history in these settings.…”

The Proto‐Zagros Foreland Basin in Lorestan, Western Iran: Insights From Multimineral Detrital Geothermochronometric and Trace Elemental Provenance Analysis

“…No common Pb correction was applied due to isobaric interference with 204 Hg. Following LA-ICP-MS age and trace elemental analysis, representative zircon grains from each major U-Pb age peak were selected for (U-Th)/He dating to further characterize the source terrane's cooling histories (e.g., Reiners et al, 2005;Thomson et al, 2017). Glass NIST612 was used as a primary reference material and 29 Si as an internal standard following the procedures of Marsh and Stockli (2015).…”

“…Despite this remarkable revolution in zircon-based isotopic provenance analysis, the DZ U-Pb provenance approach may have some limitations due to variable zircon fertility among different rock types (strong bias toward felsic igneous rocks), spatially homogeneous or nondiagnostic source terrane U-Pb age signatures, or complex recycling and mixing (e.g., Capaldi et al, 2017;Malusà et al, 2016;Moecher & Samson, 2006). Some of these possible ambiguities have been (partially) mitigated through the combination with other isotopic or chronometric techniques such as Hf isotopes or (U-Th)/He dating, adding additional provenance metrics for individual grains (e.g., Gerdes & Zeh, 2006;Reiners et al, 2005;Thomson et al, 2017). Although these additional isotopic constraints can elucidate the tectonothermal evolution of the source area, they generally do not provide any petrogenetic information of the source terrane or parent rock.…”