Abstract

The residual glass in specimens of Deccan Trap basalt collected from widespread areas in western and central India shows evidence for the existence of two immiscible silicate liquids, now preserved as globules (0.002 to 0.010 mm in diameter) of dark-brown glass in a groundmass of colorless or light-brown glass. Such clear evidence for the existence of silicate liquid immiscibility was first noted by Roedder and Weiblen (1970a) in the Apollo 11 lunar rocks and subsequently in four occurrences in the United States and Greenland.

It is postulated, because of widespread occurrence of liquid immiscibility in the Deccan Traps, that liquid immiscibility should play a significant role in similar igneous magmas in the very late stages of differentiation in a closed system. The ferrodiorite specimens of the Upper Zone of the Skaergaard intrusion show four lines of evidence which indicate the possibility that their iron enrichment might have been partly caused by settling of high-iron immiscible silicate liquid globules.

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