An integrated geophysical and geological study of the Monturaqui impact crater, Chile

Abstract

The newly acquired gravity data shows a negative anomaly of 1 mGal at the center and allowed the creation of a 3-D model with a RMS error of <0.1 mGal, which supports the predictions of a fracturing-induced low-density granitic layer on top of the unfractured basement.

Mars MOURA magnetometer demonstration for high-resolution mapping on terrestrial analogues

“…4b). Our data show similar low magnetic anomalies of ±50 nT for the crater floor as measured by Ugalde et al (2007), whereas the eastern and north-eastern crater rim is characterised by much stronger local anomalies from −500 to > +600 nT. The transitions of the outcrops of granitic and ignimbritic target rocks shown in Fig.…”

“…At the relatively small Monturaqui crater, a coarse grid of magnetic mapping with spacings of approximately 70 m inbetween single measuring points have been previously performed with a caesium magnetometer in the crater and its surroundings by Ugalde et al (2007). The published interpolated map shows only very low magnetic anomalies in the range of less than ±200 nT with slightly higher values in the southern and eastern sector of the crater rim.…”

“…The crater was discovered in 1962 from aerial photographs and firstly described by Sánchez and Cassidy (1966). It is located at latitude 23 • 55 40 S and longitude 68 • 15 42 W at an elevation of 2984 m (Ugalde et al, 2007), has a diameter of 370 m and is 34 m deep (Fig. 4a, b, c), and was formed during the Quaternary (660 ± 90 kyr BP; Ukstins Peate et al, 2010).…”

“…Fe-Ni spherules, which have been found in impact melt/glass fragments along the eastern and western crater rim has been classified as a group I coarse octahedrite (Bunch and Cassidy, 1972;Buchwald, 1975) and contain schreibersite, cohenite, fossil taenite, and kamacite as major components as well as some troilite. Laboratory analyses of these components show both high remanent magnetization as well as very high susceptibility (Ugalde et al, 2007;Ukstins Peate et al, 2010).…”

Zircons from the Acraman impact melt rock (South Australia): Shock metamorphism, U–Pb and 40 Ar/ 39 Ar systematics, and implications for the isotopic dating of impact events

“…Previous 40 Ar/ 39 Ar dating of the melt rock failed to provide the age of the impact and rather yielded post-impact alteration ages around 450 Ma (Baldwin et al, 1991;Jourdan, 2012). Together with the much younger $18 km El'gygytgyn impact structure in NE Russia (Gurov et al, 2005;Koeberl et al, 2013), the $14 km Zhamanshin, the $8 km Bigach, and the $2.8 km Shunak impact structures in Kazakhstan (Bouška et al, 1981;Masaitis, 1999), as well as the small $350 m Monturaqui impact crater in the Chilean Andes (Ugalde et al, 2007), Acraman is one of few terrestrial impact structures that produced impactites from siliceous (i.e., andesitic to rhyolitic) volcanic target rocks.…”