Formation conditions of plagioclase-bearing type I chondrules in CO chondrites : a study of natural samples and experimental analogs
type: CreativeWork
description: Chondrites are samples from undifferentiated asteroids that contain components that formed in the early solar system. One of the components found in chondrites is chondrules, which are small igneous spherules that formed from the melting of precursor dust ball assemblages during very short, high-temperature events in the solar nebula. Chondrules typically contain olivine and pyroxene, a glassy mesostasis, Fe-Ni metal, and sulfides. Type I chondrules contain FeO-poor and volatile-poor mineral assemblages. Approximately 10% of type I chondrules, including type IA, IAB, and IB textures, also contain igneous plagioclase. While dynamic cooling experiments have put constraints on the formation conditions of chondrules based on olivine and pyroxene textures and morphologies, plagioclase has not been produced in previous experimental chondrule analogs. In this study, we investigated common chondrule textures in CO chondrites and determined mineral and bulk compositions for plagioclase-bearing type I chondrules in CO chondrites. We also performed one-atmosphere dynamic cooling experiments in order to establish formation conditions for type I chondrules. We attempted to optimize conditions for plagioclase nucleation and growth by conducting experiments at slow cooling rates, low quench temperatures, in the presence of a Na-rich atmosphere, and with anorthite seeds present in the starting material. Experimental run products closely resemble textures of type I chondrules in ordinary and carbonaceous chondrites. Olivine is commonly poikilitically enclosed in euhedral low-Ca pyroxene. Ca-pyroxene appears as overgrowths on larger low-Ca pyroxene grains. Compositions of olivine, pyroxene, and mesostasis from experimental charges are also very similar to those observed in natural chondrules. Therefore, peak temperatures (1500 - 1600°C) and slow cooling rates (5 - 25°C/hr) used are plausible conditions for type I chondrule formation. These conditions are also predicted by the shock w…
abstract: Chondrites are samples from undifferentiated asteroids that contain components that formed in the early solar system. One of the components found in chondrites is chondrules, which are small igneous spherules that formed from the melting of precursor dust ball assemblages during very short, high-temperature events in the solar nebula. Chondrules typically contain olivine and pyroxene, a glassy mesostasis, Fe-Ni metal, and sulfides. Type I chondrules contain FeO-poor and volatile-poor mineral assemblages. Approximately 10% of type I chondrules, including type IA, IAB, and IB textures, also contain igneous plagioclase. While dynamic cooling experiments have put constraints on the formation conditions of chondrules based on olivine and pyroxene textures and morphologies, plagioclase has not been produced in previous experimental chondrule analogs. In this study, we investigated common chondrule textures in CO chondrites and determined mineral and bulk compositions for plagioclase-bearing type I chondrules in CO chondrites. We also performed one-atmosphere dynamic cooling experiments in order to establish formation conditions for type I chondrules. We attempted to optimize conditions for plagioclase nucleation and growth by conducting experiments at slow cooling rates, low quench temperatures, in the presence of a Na-rich atmosphere, and with anorthite seeds present in the starting material. Experimental run products closely resemble textures of type I chondrules in ordinary and carbonaceous chondrites. Olivine is commonly poikilitically enclosed in euhedral low-Ca pyroxene. Ca-pyroxene appears as overgrowths on larger low-Ca pyroxene grains. Compositions of olivine, pyroxene, and mesostasis from experimental charges are also very similar to those observed in natural chondrules. Therefore, peak temperatures (1500 - 1600°C) and slow cooling rates (5 - 25°C/hr) used are plausible conditions for type I chondrule formation. These conditions are also predicted by the shock w…
author: Wick, Molly
language: English
keywords: Chondrule, Petrology, Chondrite, Experiment, Kainsaz, CO
date published: 2011-06-01T07:00:00Z
date modified: 2026-07-24T05:26:22Z
provider: University of New Mexico
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of New Mexico

PropertyValue
property ID: Handle
value: http://hdl.handle.net/1928/12629