T176 Petrochronology: Advances and Applications to Petrogenesis and Tectonics (Posters)

Monday, 23 October 2017
9:00 AM - 6:30 PM
Halls 4EF

ECLOGITE CLASTS OF THE TERTIARY PIEDMONT BASIN, LIGURIAN ALPS, ITALY: RB-SR GEO/THERMOCHRONOLOGIC CONSTRAINTS ON EXHUMATION RATES

Paper number: T176-22
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Voltri Massif (VM) and Tertiary Piedmont Basin (TPB), Ligurian Alps, Italy preserve a unique geologic relationship: eclogite-facies metamorphic rocks (VM) directly overlain by sediments containing eclogite clasts (TPB). In this setting, high-precision exhumation rates, not dependent on low-temperature thermochronology, can be determined by combining the P-T-t history of eclogite clasts and the depositional age of sediments. These rates directly inform tectonic models for the assembly of the Alps and the mechanisms by which high-pressure low-temperature metamorphic rocks are exhumed. Furthermore, TPB eclogites provide information on eroded units which previously overlied the VM. However, TPB eclogite clasts are particularly intractable to U-Pb and 40Ar/39Ar dating methods. This study presents new Rb-Sr based geochronologic data for VM eclogites and TPB eclogite clasts. New Oligo-Miocene white mica-whole rock Rb-Sr dates from metasedimentary clasts agree with previous U-Pb baddeleyite dates determined from the VM. Further analysis of mafic eclogites and screening of micas based on Si content will examine the effects of greenschist retrogression on reported Rb-Sr dates.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-306886

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