Based on stratigraphy, 40Ar/39Ar ages, lithofacies, trace and Sr isotopes geochemistry, and NRM directions, we correlate three main calc-alkaline to alkaline rhyolitic ignimbrites, located in and around the Arequipa depression (Paquereau et al., in press): the Rio Chili ignimbrite (RCI, ca. 13.33 Ma), the voluminous (16-24 km3) and extended (800 km2) La Joya ignimbrite (LJI, ca. 4.87 Ma), covers a large area within the Altiplano at 4500 masl.down to less than 2000 masl. south-west of the Arequipa Batholith; and the thick Arequipa Airport ignimbrite (AAI, ca. 1.65 Ma, 20 km3) consists of a lower white and an upper pink units, which fill the Arequipa depression (between 2600 and 2200 masl.) to the west of the city of Arequipa. Anisotropy of magnetic susceptibility (AMS) and characteristic remanence were measured for 52 sites located principally in the voluminous LJI and AAI as well as variation of physical properties (density, porosity, uniaxial compressive strength) of the deposits. This study deals with the magnetic properties of the deposits which help to identify the magnetic minerals and their properties and variations in and between the AAI and the LJI. Secondarily, we present variations of physical properties and magnetic properties along a 40 m thick section of the AAI, in order to map welding and recrystallisation intensities variation. The third aim focuses on Anisotropy of Magnetic Susceptibility (AMS), used to evaluate the flow directions and the transport and depositional properties of the AAI and LJI.
Paquereau, P., Roperch, P., Thouret, J.C., Giordano, D., Russell, K. (2004). Neogene ignimbrites in the area of Arequipa, southern Peru: paleomagnetism and welding.
Neogene ignimbrites in the area of Arequipa, southern Peru: paleomagnetism and welding
GIORDANO, Daniele;
2004-01-01
Abstract
Based on stratigraphy, 40Ar/39Ar ages, lithofacies, trace and Sr isotopes geochemistry, and NRM directions, we correlate three main calc-alkaline to alkaline rhyolitic ignimbrites, located in and around the Arequipa depression (Paquereau et al., in press): the Rio Chili ignimbrite (RCI, ca. 13.33 Ma), the voluminous (16-24 km3) and extended (800 km2) La Joya ignimbrite (LJI, ca. 4.87 Ma), covers a large area within the Altiplano at 4500 masl.down to less than 2000 masl. south-west of the Arequipa Batholith; and the thick Arequipa Airport ignimbrite (AAI, ca. 1.65 Ma, 20 km3) consists of a lower white and an upper pink units, which fill the Arequipa depression (between 2600 and 2200 masl.) to the west of the city of Arequipa. Anisotropy of magnetic susceptibility (AMS) and characteristic remanence were measured for 52 sites located principally in the voluminous LJI and AAI as well as variation of physical properties (density, porosity, uniaxial compressive strength) of the deposits. This study deals with the magnetic properties of the deposits which help to identify the magnetic minerals and their properties and variations in and between the AAI and the LJI. Secondarily, we present variations of physical properties and magnetic properties along a 40 m thick section of the AAI, in order to map welding and recrystallisation intensities variation. The third aim focuses on Anisotropy of Magnetic Susceptibility (AMS), used to evaluate the flow directions and the transport and depositional properties of the AAI and LJI.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
