INVESTIGATION OF A POSSIBLE LINK BETWEEN EXTERNAL MORPHOLOGY AND INTERNAL TEXTURE IN IMPACT MELT EJECTA FROM MONTURAQUI CRATER, CHILE

Monturaqui Crater, located in the northern Atacama Desert of Chile, is a classic example of a small, well-preserved meteorite impact crater with a simple granitic target lithology and dark impactite ejecta. Monturaqui impactite, comprised of mineral and lithic clasts bonded by vesicular impact melt glass, has been previously analyzed but no detailed study of morphology has been undertaken. Morphology has hitherto been dismissed as a tool for classifying impact melt due to the similarity of interior textures of impact melt from Barringer Meteor Crater, AZ despite external morphological heterogeneity. It has been postulated that morphology may thus have little genetic significance in spite of noted evidence for heterogeneous mixing during the impact process. This study aims to characterize external morphology and interior textures and relate them to spatial distribution around the crater in order to investigate the possible link between them. Additionally, the exploration of such a link may provide insight into small-scale processes occurring during impact events.

Over sixty external morphological textures have been identified in Monturaqui impactite using optical and scanning electron microscopy and characterization of internal textures is ongoing. Abundance and composition of mineral and lithic clasts within the impact melt are variable and vesicle size and shape distributions also vary from rim to core in most samples. Fracture patterns present externally may additionally be related to the interior change in vesicularity. Coupled with fracture patterns, the change in vesicularity may reflect a complex cooling history of the impactite while it was being ballistically emplaced around the crater. Further characterization is needed to quantify the relationship between external morphology, internal texture, and spatial distribution, and more significantly to verify if such a link exists.