Page:The Journal of geology (IA journalofgeology11893univers).pdf/177

or segregations, of both the feldspathic and phosphatic types of augite-syenite in a phonolitic nephelinite, apparently without feldspar. The bulk of the iron ore at this place occurs as rounded nodular segregations associated with apatite in a decomposed rock which was evidently coarse grained and micaceous. This was evidently not jacupirangite, but apparently some peculiar type of nepheline or augite-syenite. Except for the absece of black garnets it apparently corresponds closely with the ore-bearing rock of Magnet Cove, Ark., described by the late Dr. J. F. Williams. It may be noted in this connection that the same character (absence of black garnet) distinguishes the jacupirangite from the ijolith of Ramsay and Berghell.

As in the Caldas region, there is at Ipanema evidence that the eruptive action took place in the late Carboniferous or post-Carboniferous times. This coincidence of age at two of the localities may perhaps justify the assumption (which cannot be directly proven for lack at the other places of sedimentaries intermediate between the very ancient and the very modern), that all of these eruptive centers are substantially contemporaneous. Bearing on this question of age, as also on that of consanguinity, is the fact that in a region characterized by Devonian and probably also Carboniferous strata in Paraguay, Pohlmann has reported nepheline-bearing basalt, and Dr. J. W. Evans has lately communicated specimens of foyaite and augite-syenite from Pāo de Assucar on the Paraguay, proving that this mass, hitherto reputed to be granitic, represents another eruptive center similar to those studied in eastern Brazil.

The evidence of consanguinity of foyaite and phonolite consists of an intimate association within limited areas at all of the localities mentioned, except Ipanema, where neither type has as yet been found in a condition to be positively identified; of a direct passage to phonolite at the margins of foyaite masses at Caldas; of inclusions of phonolite in foyaite at the same place and conversely of inclusions, evidently formed in situ of foyaite in phonolite at Caldas and Tingua. In this connection may be mentioned an inclusion of the type of