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An igneous rock composed primarily of alkali feldspar together with other minerals, such as hornblende.

[Latin Syēnītēs (lapis), (stone) of Syene, from Syēnē, Syene, an ancient city of southern Egypt, from Greek Suēnē.]

sy′e·nit′ic (-nĭt′ĭk) adj.
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7] At the cataracts of the great rivers Orinoco, Nile, and Congo, the syenitic rocks are coated by a black substance, appearing as if they had been polished with plumbago.
In contrast the A-type syenitic and metavolcanic rocks are probably related to the compositionally similar West Barneys River plutonic suite and younger volcanic rocks formed in an extensional regime.
Kipawa syenitic complex is typically enriched in heavy rare earth elements (HREE), Zirconium, and, in places, other rare metals are found, such as Niobium (only niobium and zirconium concentrations are noted in public files).
At Twin Peaks, located at the north end of the Hope Bay belt, argillaceous sediments unconformably overlie volcanics and syenitic intrusives adjacent to a major lineament, an area where surface sampling in 2001 returned anomalous gold values up to 0.
Carbonatites are plutonic rocks from great depth and occur with syenitic intrusions and amongst more exotic minerals can also carry copper-silver and gold.
Numerous gold showings exist in highly favourable structures associated with syenitic intrusives, shear zones, and sedimentary horizons.
Granosyenitic, syenitic, and quartz monzonitic rocks (mangeritic rocks after Bogatikov & Birkis, 1973) and associated gabbro-anorthosites and ultramafic rocks are found in the southern part of the batholith (Fig.
The relatively coarse grain size of xenoliths and xenocrysts indicate origin from subjacent plutonic sources, and the gabbro of Christmas Mountain and syenitic rocks of Dominguez Mountain show that such plutons exist in the Big Bend region.
Cadillac West objectives in this program were: to test for east and west extensions of north-and south-dipping zones previously mined in the Francoeur and Arntfield deposits, to explore for feeder systems under the Lac Fortune deposit, and to explore for mineralization relating to a major syenitic intrusion along the Cadillac Break where this historically prolific structure is largely obscured by Proterozoic sediments.
In order of decreasing age they are (1) agmatite containing blocks of host rock in a coarse-grained igneous matrix, (2) felsite, rhyolite porphyry, and microgranite, (3) layered and massive gabbro, (4) medium- to coarse-grained amphibolebiotite granite, (5) heterogeneous mafic rocks with a generally dioritic to tonalitic matrix containing schliers and blocks ranging from layered gabbro, to monzonitic, syenitic and granitic varieties.
Petrographic studies of these samples also suggest that the skarn zone has been created by the presence of a nearby intrusive, possibly of syenitic composition, which implies that the skarn zone may be of substantial size.