On a possible parent crater for Australasian tektites: Geochemical, isotopic, geographical and other constraints

Tektites are natural glasses formed by the melting of Earth's surface materials during the impact of a large extraterrestrial body. At present, they are found in four main strewn fields associated with separate impacts: Central European (moldavites), Australasian (australites, indochinites, philippinites, javaites, etc.), North American (georgiaites and bediasites), and West African tektites from the Ivory Coast (ivorites). The location of the impact site and parent crater for Australasian tektites (AAT) has remained an unanswered question for decades. The current review discusses possible locations of the AAT parent crater on the basis of published geochemical, mineralogical, petrographic and isotopic data on both AAT and potential source materials. This was aided by new geochemical data for a representative set of AAT covering the main morphological types and parts of the AAT strewn field, and also assumes some ballistic, palaeogeographic, palaeoclimatic and palaeoecological constraints. The review focuses particularly on three parallel tasks: 1) collecting comprehensive data (geochemical composition, Sr, Nd, Rb, Li, and B isotopes, and cosmogenic 10Be) for revisiting Chinese loess or its precursors as the most suitable source materials for AAT; 2) criticisms of the generally accepted location of the impact in Southeast Asia (Indochina) based mainly on a lack of suitable targets and a mismatch between the geochemical and isotopic compositions of AAT and prevailing sedimentary targets in Indochina; 3) supporting evidence, in addition to 1), for a hypothesis locating the AAT parent crater to the arid area of Northwest China, which could provide a sufficient supply of suitable source materials as well as ideal conditions for burial of the crater under the tallest megadunes on Earth.