IDENTIFICATION AND QUANTITATIVE ANALYSIS OF CHONDRULES IN ORDINARY AND CARBONACEOUS CHONDRITE METEORITES

Meteorites are believed to tell the story of the early solar system in their compositions and textures that formed around 4.5 billion years ago. Meteorites are classified based on differences in composition and texture into stony, stony-iron, and iron groups. The stony group is further classified into ordinary chondrites, carbonaceous chondrites, and achondrites. This study looks at the occurrence of chondrules in both ordinary and carbonaceous chondrites. Chondrite meteorites contain chondrules, small spherical structures with ferromagnesian minerals such as olivine, pyroxene, or the equivalent glass. Chondrules may be recognized on a cut and polished surface by their boundaries with the surrounding matrix using a simple hand lens or binocular microscope. By looking at these chondrites we are able to map out the occurrence, size, and distribution of chondrules that are present within the meteorites. Cut and polished samples of ordinary and carbonaceous chondrite meteorites were used including the Sahara 97210 L(LL)3.5 and Allende CV3. High-resolution images of the meteorite surfaces were collected and imported into ArcGIS for analysis. Chondrules were identified on the images and marked as polygons in ArcMap. Resulting data for each polygon included the area and perimeter. The percent area of chondrules represented on the prepared surface was calculated from the total area and the individual polygon areas. Roundness was calculated as a function of area compared to perimeter where a circle is equal to 1.00 and a square to 0.88. Diameters of the chondrules were also calculated from the polygon areas in comparison to measurements of a large, circular chondrule in the sample. The information gathered from the Sahara 97210 sample had 28% of the area of the meteorite filled with chondrules. The average roundness of all the chondrules from Sahara 97210 is 0.954 with a standard deviation of 0.035. Out of 220 chondrules that were mapped, the average diameter is 0.734 mm with a range of 3.6mm to 0.162 mm. When looking at the figures from the Allende chondrite it had almost 17% of the area filled with chondrites with an average diameter of the chondrules of 1.17 mm. The average roundness of the 194 chondrules of the Allende is 0.947 with a standard deviation of 0.033.