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Journal of Petrology | Volume 43 | Number 10 | Pages 1979-1983 | 2002
© Oxford University Press 2002

The Plagioclase–Magma Density Paradox Re-examined and the Crystallization of Proterozoic Anorthosites: a Reply

JAMES S. SCOATES*

DEPARTMENT OF EARTH AND OCEAN SCIENCES, UNIVERSITY OF BRITISH COLUMBIA, 6339 STORES ROAD, VANCOUVER, B.C., V6T 1Z4, CANADA

Received December 30, 2001; Revised typescript accepted March 27, 2002

The first 150 words of the full text of this article appear below.


   INTRODUCTION
 
The primary goals of the work presented in Scoates (2000) were to evaluate the potential density contrasts between the mafic blocks and their hosting anorthositic cumulates in the 1·43 Ga Poe Mountain anorthosite and to place constraints on the crystallization histories of Proterozoic anorthosites where intermediate-composition plagioclase is the dominant liquidus mineral. After demonstrating that all of the blocks are more mafic than their hosting anorthositic cumulates, that their plagioclase compositions are more calcic, that each block is in strong Sr isotopic disequilibrium with its host, and that an asymmetric set of structures in the hosting anorthositic cumulates consistently envelops many of the blocks, I quantitatively evaluated block–magma density variations taking into account possible variations in temperature, pressure, oxygen fugacity, phosphorus contents, and reasonable estimates of H2O and CO2 contents in proposed parental and residual magma compositions. It was shown that all blocks, except one where the sample may . . . [Full Text of this Article]


   PREFERRED ORIENTATION OF THE BLOCKS
 

   PETROGRAPHIC AND CHEMICAL RELATIONS OF THE BLOCKS AND THE HOST ROCKS
 

   AN ALTERNATIVE, AND POSSIBLY MORE ACCEPTABLE, GENETIC MODEL
 

   SUMMARY AND CONCLUSIONS
 

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