On the Origin and Occurrence of Basic Bodies Associated with Discordant Bathyliths

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Abstract
It is suggested that the rock-suite, characteristic of the discordant bathyliths and ranging in composition from ultrabasic to ultra-acid, is formed from two magmas, a basaltic and a granodioritic, that the basic rocks are emplaced among the geosynclinal sediments before the introduction of the acid magma, and that intermediate rocks are hybrids. Further, it is suggested that hybridization takes place in two stages: first, by reaction between basic rocks and water and carbon dioxide, released from sediments as a result of deep-seated metamorphism, and rising in advance of the acid magma; and secondly, by the magma itself. The first intrusions carry shattered country rocks and are stock-like bodies, and these are followed by successive emplacements of granodiorite, the earliest of which envelop most of the stocks and are, thereby hybridized to form tonalites. Only those stocks near the margins of the later intrusions are preserved, and hence occur as satellites about the larger more acid bodies.The order of intrusion, the grainsize of the basic hybrids, and the occurrence of hornblende is discussed and it is concluded that dioritic rocks and dioritic magmas originate at a high level in the geosynclinal pile.

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