psammitic


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psammitic

[sə′mid·ik]
(geology)
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The Bras d'Or terrane is characterized by three main rock associations: metamorphic and igneous rocks, comprising gneiss formed at high metamorphic grade but relatively low pressure of metamorphism from pelitic to psammitic protoliths, and incorporating thin layers of marble and amphibolite; lower metamorphic grade dominantly clastic metasedimentary rocks, but also including minor calcareous and mafic components; and a suite of late Neoproterozoic calc-alkaline plutons and associated volcanic rocks (Raeside and Barr 1992).
The package lies within the Company's 1035L licence, located approximately 5km to the northwest of the proposed Tete pig iron project operation and belongs to the Mid-Proterozoic aged Chidue Formation, comprising a metamorphosed package of terrestrial and shallow marine sediments dominated by psammitic schists and marbles.
From drill core and geophysical data, Grid 5 basement lithologies have now been confirmed to consist of mostly semi-pelitic to psammitic assemblage of rock units, containing a central unit of graphitic pelites.
Figure 5 demonstrates results of a progressive water-saturated melting of a mixed metasedimentary source consisting of a 50:50 mixture of psammitic and pelitic rocks from the Proterozoic Halls Creek sedimentary sequence, Kimberley region, Australia.
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 Bendigo reefs comprise sub vertical lodes in psammitic or semi-psammitic schist.
The rock types include garnet-biotite gneiss, amphibolite and both pelitic and psammitic metamorphosed sediments.
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).
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.
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.