Reclassification of Hart and Northwest Africa 6047: Criteria for distinguishing between CV and CK3 chondrites.

· by · in , , ,

Dunn, T. L. and Gross, J.

Meteoritics & Planetary Science. doi: 10.1111/maps.12946

LINK

“The single parent body model for the CV and CK chondrites (Greenwood et al. ) was challenged by Dunn et al. (), who argued that magnetite compositions could not be reconciled by a single metamorphic sequence (i.e., CV3 CK3 CK4–6). Cr isotopic compositions, which are distinguishable between the CV and CK chondrites, also support two different parent bodies (Yin et al. ). Despite this, there are many petrographic and mineralogical similarities between the unequilibrated (petrologic type 3) CK chondrites and the CV chondrites (also type 3), which may result in misclassification of samples. Hart and Northwest Africa 6047 (NWA 6047) are an excellent example of this. In this study, we revisit the classification of Hart and NWA 6047 using magnetite compositions, petrography, and compositions of olivine, the most ubiquitous mineral in both CV and CK chondrites. Not only do our results suggest that NWA 6047 and Hart were misclassified, but our assessment of CV and CK3 chondrites has also led to the development of criteria that can be used to distinguish between CV and CK3 chondrites. These criteria include: abundances of Cr2O3, TiO2, NiO, and Al2O3 in magnetite; Fa content and NiO abundance of matrix olivine; FeO content of chondrules; and the chondrule:matrix ratio. Classification as a CV chondrite is also supported by the presence of igneous chondrule rims, calcium-aluminum-rich inclusions, and an elongated petrofabric. However, none of these petrographic characteristics can be used conclusively to distinguish between CV and CK3 chondrites.”

Related posts (automatically generated):

  1. A reclassification of Northwest Africa 2900 from CV3 to CK3 chondrite
  2. Oxygen isotope systematics of chondrule olivine, pyroxene, and plagioclase in one of the most pristine CV3Red chondrites (Northwest Africa 8613)
  3. Diversity Among EH Chondrites: Anomalous EH3 Chondrite Northwest Africa 8789 and Rare EH Melt Rocks Northwest Africa 7324 and Northwest Africa 10237
  4. Northwest Africa 8418: The first CV4 chondrite
  5. Reassessing the Formation of CK7 Northwest Africa (NWA) 8186
  6. Northwest Africa 5958: A Weakly Altered C2 Ungrouped Chondrite
  7. Northwest Africa 8418: A CV4 Chondrite, with New Insights into Secondary Processes on the CV Parent Body
  8. Mapping the composition of chondritic meteorite Northwest Africa 3118 with micro-Raman spectroscopy
  9. Mineralogical and oxygen isotopic study of a new ultrarefractory inclusion in the Northwest Africa 3118 CV3 chondrite
  10. Magnetite in the unequilibrated CK chondrites: Implications for metamorphism and new insights into the relationship between the CV and CK chondrites.
Tags: ,