Abstract

Classification of meteorites: The big quantity of official chilean meteorites, 886 at present [1], and the possibility to find more in the Atacama desert surfaces [2] have brought the challenge to make grow Meteoritcs in Chile if we want to keep increasing the findings and improve the science done with them. For that, the first step was to create an official repository and be able to classify the meteorites. To do this, the standard classification of ordinary chondrites, the most abundant type in the collection (89%), includes petrologic description of main components and textures [3], shock stage [4] and weathering grade [5], most of them done with a petrographic microscope, but to obtain the ordinary chondrite chemical classes (LL - very low iron content, L - low iron content and H - high iron content), the procedure considers the value of fayalite, Fa, in olivines and ferrosilite, Fs, in low-Ca pyroxenes, which are measured with a microprobe. For large amounts of samples, as the ones collected in the Atacama, the use of microprobe is an expensive technique, adding the fact that in South America there are only a few microprobes fully operatives. The work of [6] proposed an alternative method to assign the chemical classes, complementary to the other classification parameters, using the magnetic susceptibility parameter (expressed as log X), useful when the meteorites have low weathering degrees (W<3), as the total metal content in the meteorite (that gives the class) is correlated with the magnetic phases present, and the weathering degree reflects mostly the replacement of the main magnetism carriers (kamacite-taenite and troilite) to Fe oxi- hydroxides. Chilean repository. We recently started at the Astro Engineering Center UC the first scientific repository of meteorites, storing samples coming from expeditions to the Atacama Desert, and donations, and now we are developing a laboratory network between Chilean institutions to be able to classify new meteorites that include UCH, UACH and U. Católica del Norte. Magnetic Susceptibility Method (MSM). To implement this inexpensive, non-destructive and easy technique we have been performing comparison tests of already classified meteorites to calibrate results at the Paleomagnetism Laboratories at UCH and UACH using the procedures of [6,7], whose results will be presented at the conference. In the ordinary chondrite fraction of the collection there are 36% of W2, 28% of W1, 27% of W3, 7% of W4, and a 17% with no clear weathering grade classification, making a 64% of these meteorites viable for the MSM, and letting only ~35% of them in the status of requiring microprobe analysis.