Chondrules in the Tieschitz Chondrite: A Chemical-Petrographic Approach

Introduction: Although large amounts of petrological and geochemical data on chondrules exist, there is still no consensus, neither on the different processes that were active during and after chondrule formation, nor on the nature of the processes that give rise to liquid droplets [e.g., 1]. However, most of the scientists working on chondrules today believe that crystals in chondrules are precipitation products of the liquid (e.g., melt) and that mesostasis represents residual liquid of the bulk melt. Here we compare the texture of three chondrules from the UOC Tieschitz L/H3.6 (PTS, Tieschitz L 3441-3443, NHMV) with the chemical composition of their clear glassy mesostasis (residual melt?) in order to contribute to our knowledge of the chondrule forming mechanism. Results: Tieschitz 3-(2) is a PO chondrule [glass: 13 %, euhedral Ol (Fo98): 87%], 2.3 mm in apparent diameter and containing several metal and sulfide belts and diffusion controlled aggregation at the surface (lobate surface). Tieschitz L(A) is a POP chondrule (diameter: 680 μm) with a rim of low-Ca pyroxene [glass: 3.6%, Ol (Fo98): 51%, Px (En97.6, Fs1.4): 45%]. Tieschitz XII is a glass-rich (glass: 64%) chondrule that contains olivine plates (16.5%), Ca-rich pyroxene (2.5%), sulfide dendrites, and a large spinel that is surrounded by a cryptocrystalline matrix (16.5%) [2]. Normalized REE abundance patterns of the glassy mesostasis are shown in the figure.