psammitic


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psammitic

[sə′mid·ik]
(geology)
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The assemblage of pelitic, psammitic, and carbonate rocks indicates that a passive margin in a tropical climate was quickly changed to an active Andean-type continental margin in which voluminous calc-alkaline dioritic to granitic plutons were emplaced.
Both rock types are of semipelitic to psammitic composition.
Semipelitic to psammitic composition of metatexites in borehole Js-799 alternates on the order of magnitude of 0.
In contrast to other areas of the George River Metamorphic Suite which include carbonate as well as clastic rocks, the rocks in the Glen Tosh formation are psammitic and semi-pelitic, consisting dominantly of sutured quartz and feldspar, with variable but generally small (<10%) amounts of biotite and muscovite, with accessory apatite, tourmaline, and opaque minerals.
The dioritic suite occurs mainly in the area between the gneissic and psammitic units of the Glen Tosh formation.
The rock types include garnet-biotite gneiss, amphibolite and both pelitic and psammitic metamorphosed sediments.
For the interpreted lithological variations, zones of elevated gravity have been interpreted as denser, carbonate rich units, with the lower response area indicating pelitic or psammitic units or areas of deeper oxidation or younger cover.
The Goldenville and Halifax groups in the northwestern area have a lower quartz/feldspar ratio in psammitic rocks and contain more volcanic debris than those in the southeastern area (White 2010).
These basal Tetagouche strata occur within the transition from a deep-water fan complex of quartzose psammitic and pelitic turbidites of the Miramichi Group (Rice and van Staal 1992) and deposition of the overlying volcanic-chertgreywacke assemblage of the Ordovician Tetagouche Group, a transition representing the change from a stable continental margin to an unstable volcanic back-arc setting marked by rifting, local uplift and erosion, followed by mainly felsic volcanism and subsidence.
Microscopic deformation mechanisms associated with mica film formation in cleaved psammitic rocks.