A Precambrian fayalite granite from the south coast of Western Australia

Stephenson, N. C. N.; Hensel, H. D.

doi:10.1016/0024-4937(78)90021-x

Cited by 10 publications

(2 citation statements)

References 31 publications

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“…QFM). This is depicted in Figure 6 and also has been found to be true for other anorogenic complexes, both Proterozoic (Stephenson and Hensel, 1978) and Phanerozoic (Czamanske et al, 1977;Wones, 1980). Yet, the numerous granites that comprise the anorogenic magnetite-series are notable exceptions to this generalization.…”

Section: Intensive Variablessupporting

confidence: 67%

Proterozoic anorogenic granite plutonism of North America

Anderson

1983

Geological Society of America Memoirs

412

188

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Anorogenic magnatic activity characterizes much of the late to mid-Proterozoic, from 1030 to 1770 m.y. ago, in a broad belt trending from the southwestern United States, northeastward through Labrador, across southern Greenland, and into the Baltic shield. The association of gabbroic to anorthositic rocks, a separate mangeritic series of primarily intermediate composition, and granite of definite rapakivi affinity comprise an anorogenic "trinity" of world-wide occurrence. With the exception of the 1.76 b.y. Montello batholith (Wisconsin), this episode in North America is restricted to the interval 1.0 to 1.5 b.y. and occurs in three distinct events. Over 70 percent of Proterozoic anorogenic magmatism occurs in a 1.41 to 1.49 b.y. old 600-1000 km wide belt trending from southern California to Labrador that volumetrically and age-wise is totally a North American phenomenon. Renewed anorogenic granite magmatism occurred form 1.34 to 1.41 and from 1.03 to 1.08 b.y. ago in lesser proportions. Although anorthositic and mangeritic rocks are abundant in some provinces (e.g., Labrador), rapakivi granite (in the broad usage of the term) represents by far the most abundant magma-type generated during this nonorogenic period.The modal and mineral composition of these granitic rocks is distinctive and reflects the potassic and iron-enriched character of the magmas and the unique conditions under which crystallization occurred. Principal rock types include biotite ± hornblende granite to adamellite although numerous peraluminous, two-mica (biotite + celadonitic muscovite ± garnet) granites also occur. Crystallization of these epizonal granitic magmas occurred over the range of 640 to 790° C at low total pressures (most less than 2 kb) and at relatively dry conditions. A dramatic difference in crystallization conditions lies with the level of oxygen fugacity which ranges three orders of magnitude from low (ca. QFM) to high (above Ni-NiO), resulting in systematic differences in Fe-Ti oxide mineralogy and mafic silicate composition.Compositionally, the granite magmas are subalkalic and marginally peraluminous (peralkaline varieties are rare to nonexistent). Although some hastingsite or riebeckite-bearing granites may have been derived from fractional crystallization of the mangeritic series, most are primary melts derived from fusion of lower crust material. The high potassium, Fe/Mg, Ba, and rare earth element (REE) composition of the granites is consistent with small degrees of fusion (10-30 percent) of calcalkaline crust of quartz dioritic, tonalitic, and granodioritic material. Initial Sr isotopic ratios average 0.7051 ± .0025. The relatively low ratios are the result of short residence times (commonly 170 to 340 m.y.) with much of the crustal source being formed in a preceding orogenic event. An earlier melting episode need not have occurred for the source. The dry nature of the magmas is due to vapor under-133 134 J. L. Anderson saturated melting of a metaigneous source with a total water budget less than 1 percent and tied...

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Section: Intensive Variablessupporting

confidence: 67%

Proterozoic anorogenic granite plutonism of North America

Anderson

1983

Geological Society of America Memoirs

412

188

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“…Igneous rocks. Fayalite is a characteristic mineral of ferruginous intraplate granitoids and granite pegmatites of increased potassium alkalinity (rapakivi granites, granitoids of the anorthosite-mangeritecharnockite-granite series, granites of anorogenic ring complexes) and syenites (Zavaritsky, 1955;Howard et al, 1966;Stevenson and Hensel, 1978;Deer et al, 1982;Krivdik et al, 1988;Frost et al, 1988Frost et al, , 1999Njonfang and Moreau, 2000;Mücke, 2003). Fayalite is also characteristic of silicic alkaline volcanics such as pantellerites (Zavaritsky, 1955;Deer et al, 1982;Civetta et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Intrusive of Post-Islandarc Fayalite Plagiogranites of the Mount Kastel in the Crimean Cimmerides

Spiridonov

Putintseva²

2021

Moscow Univ. Geol. Bull.

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A hypabyssal intrusive of fayalite plagiogranites of Mount Kastel intruded into the Yuzhnoberezhny uplift of the Gorno-Crimean tectonic Zone of the Crimean Cimmerids. Plagiogranites cross and contact metamorphosed intensivly dislocated flysch strata of the Taurian series T 2 -J 1 , the bodies of island arc gabbroids of the Early Bajocian Pervomaisko-Ayudag complex, and basalts of the Late Bajocian Karadag volcanic series. Judging by the fracture pattern and the nature of the contacts, the intrusive is relatively weakly tectonized. Post-arc plagiogranites of the Mount Kastel intrusive (SiO 2 72.02 wt %; Na 2 O, 4.57; K 2 O, 1.26; Na 2 O : K 2 O = 3.6; ferrugious rocks -92.4%; Th @ U) contain high Fe olivine-fayalite and ferrohortonolite, eulite, and annite, as well as abundant accessory, zircon, monazite-Ce, xenotime-Y. In crystallization differentiation of plagiogranites in the Kastel intrusive, Fe and Mn accumulated in olivine, Na and K in plagioclase, Mn in ilmenite, Hf in zircon, and Th in monazite; the field of solid solutions of zircon and xenotime narrowed. Endemic fayalite plagiogranites could have arisen under the conditions of an orogenic regime, which apparently follows the geological history of the Crimean Cimmerids.

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Origin of fayalite granitoids: New insights from the Cobquecura Pluton, Chile, and its metapelitic xenoliths

Vásquez¹,

Glodny²,

Franz³

et al. 2009

Lithos

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Fayalite granitoids of the Cobquecura Pluton, Central Chile, occur in an active continental margin setting, which is unusual for such rocks. They are closely associated with gabbros, and both lithologies contain hercynite-rich, Fe-rich metapelitic xenoliths. The primitive magmas of the Cobquecura Pluton are derived from a mafic source, similar to the regional subarc subcontinental mantle. Sr-Nd-Pb isotope data demonstrate that crustal contributions were important in the petrogenesis of the fayalite granitoids. The crustal contribution, however, does not consist of rocks similar to the regionally exposed Paleozoic basement rocks, but rather resembles partial melts derived from metapelitic rocks at depth. The corresponding restites are the hercynite-rich xenoliths. A relatively high content of rare earth elements and high field strength elements in the fayalite granitoids is linked to selective assimilation of crust. This is evident from the abundant xenoliths that are entrained in the fayalite granitoids, and whose leucosomes are rich in accessory minerals carrying these elements. Such Fe-rich rocks similar to the hercynite-rich xenoliths could have acted as a chemical buffer keeping the oxygen fugacity low, which is crucial for the generation of fayalite bearing granitoids.

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A Precambrian fayalite granite from the south coast of Western Australia

Cited by 10 publications

References 31 publications

Proterozoic anorogenic granite plutonism of North America

Proterozoic anorogenic granite plutonism of North America

Intrusive of Post-Islandarc Fayalite Plagiogranites of the Mount Kastel in the Crimean Cimmerides

Origin of fayalite granitoids: New insights from the Cobquecura Pluton, Chile, and its metapelitic xenoliths

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