Magmatic epidote and its petrologic significance

Zen, E‐an; Hammarstrom, Jane M.

doi:10.1130/0091-7613(1984)12<515:meaips>2.0.co;2

Cited by 296 publications

(172 citation statements)

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“…Some crystals have a core of allanite and a rim of euhedral epidote. Therefore, these features are consistent with those of magmatic epidote (Zen and Hammarstrom, 1984;Keane and Morrison, 1997). Euhedral epidote in contact with plagioclase shows corroded margins, which indicates dissolution and reaction with magma before solidification (Brandon at al., 1996).…”

Section: Petrographysupporting

confidence: 70%

Geochemistry of the Rio Espinharas hybrid complex, northeastern Brazil

Campos

Neiva

Nardi

2002

Lithos

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The Rio Espinharas pluton, northeastern Brazil, belongs to the shoshonitic series and consists mainly of syenogranite, quartz -monzonite and porphyritic quartz -monzonite, but diorite, quartz -monzodiorite, quartz -syenite and microsyenogranite also occur containing microgranular enclaves, except for the diorite. Most variation diagrams of rocks, amphiboles, biotites and allanites show linear trends, but K, Zr, Sr and Ba of rocks display curved scattered trends. The rocks ranging from diorite to syenogranite define a pseudo-errorchron and have similar REE patterns. Syenogranite and microsyenogranite are derived from two distinct pulses of granite magma with initial 87 Sr/ 86 Sr ratio of 0.7083 F 0.0003 and 0.7104 F 0.0007, respectively. Modelling of major and trace elements shows that the syenogranite evolved by fractional crystallization of plagioclase, microcline, edenite, biotite and titanite, whereas quartz -monzonite, porphyritic quartz -monzonite, quartz -monzodiorite and quartz -syenite resulted from simple mixing between an upper mantle-derived dioritic magma and the upper crust-derived syenogranite magma. Dioritic enclaves are globules of a mafic magma from the upper mantle. D

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Section: Petrographysupporting

confidence: 70%

Geochemistry of the Rio Espinharas hybrid complex, northeastern Brazil

Campos

Neiva

Nardi

2002

Lithos

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“…In agreement with textural observations on magmatic epidotes reported by Schmidt and Poli (2004), Schmidt and Thompson (1996) and Zen and Hammarstrom (1984b), the presence of epidote crystals rimming allanite cores, and their common occurrence in the interstitial sites between the rock forming minerals (amphibole, plagioclase and biotite) point towards a magmatic origin for epidote (e.g. Nalini, 1997).…”

Section: Magmatic Garnet Epidote and White Mica In The Galiléia Bathsupporting

confidence: 75%

Magmatic garnet in the Cordilleran-type Galiléia granitoids of the Araçuaí belt (Brazil): Evidence for crystallization in the lower crust

Narduzzi

Farina

Stevens

et al. 2017

Lithos

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Magmatic garnet, together with epidote, is a rare mineral association in cordilleran-I-type granitoids and of special petrogenetic significance. The metaluminous to slightly peraluminous (ASI = 0.97-1.07) Galiléia batholith (Brazil) is a large (ca. 30,000 km 2 ), Neoproterozoic (ca. 632-570 Ma) weakly foliated calc-alkaline granitoid body, characterized by the widespread occurrence of garnet (grossular 25-43 mol%) and epidote (pistacite 9.3-22.7 mol%). Field, petrographic and mineral chemical evidence indicates that garnet, epidote, biotite as well as white mica crystals (low-Si phengite), are magmatic. There is no difference in bulk rock major and trace element composition between the Galiléia granitoids and other garnet-free cordilleran-type granitoids worldwide. This evidence strongly suggests that the origin of the uncommon garnet + epidote parageneses is related to the conditions of magma crystallization, such as pressure, temperature and water content. Comparison between the mineral assemblages and mineral compositions from this study and those recorded in crystallization experiments on metaluminous calc-alkaline magmas, as well as within garnet-bearing metaluminous volcanic rocks and granitoids, indicates that the supersolidus coexistence of grossular-rich garnet, epidote and white mica is consistent with magma crystallization at pressures greater than 0.8 GPa (above 25 km depth) and at temperatures below 700°C, i.e. near the water saturated solidus. Furthermore, resorption textures around garnet (plagioclase ± quartz coronas) and epidote suggest that these minerals have been partially consumed prior to complete crystallization. These findings demonstrate that at 630 Ma the crust underneath the Araçuaí Orogen was already at least 25-30 km thick and relatively cool. However, this contrasts with the marked high heat flow registered from the neighbour Carlos Chagas Batholith located 50 km to the east. In fact such granitoids record granulite-facies metamorphism at the same pressure and time (ca. 570 Ma) of Galiléia granitoids crystallization. Thus, a more suitable geodynamic scenario is required in order to explain these two contrasting thermal regimes within the same orogen. Eventually, field, petrographic and mineral chemical analogies with similar garnet-bearing granitoids located in the fore-arc settings of the British Columbia subduction zone, possibly imply that the Galiléia granitoids represent "rare" garnet-and epidote-bearing metaluminous Cordilleran-Itype granites which can only form in a fore-arc setting.

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“…3b) and temperature ( Fig. 3c) estimates for amphibole rims are reported Zen & Hammarstrom, 1984;Vyhnal, McSween & Speer, 1991).…”

Section: Geology and Petrography Of The Mt Cer Plutonmentioning

confidence: 99%

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

et al. 2010

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-The Mt Cer Pluton, Serbia, is a complex laccolith-like intrusion (∼ 60 km 2 ), situated along the junction between the southern Pannonian Basin and northern Dinarides. It intrudes Palaeozoic metamorphic rocks causing weak to strong thermal effects. Based on modal and chemical compositions, four rock-types can be distinguished: (1) metaluminous I-type quartz monzonite/quartz monzodiorite (QMZD); (2) peraluminous S-type two-mica granite (TMG), which intrudes QMZD; (3) Stražanica granodiorite/quartz monzonite (GDS); and (4) isolated mafic enclaves (ME), found only in QMZD. 40 K-39 Ar dating and geological constraints indicate that the main quartz monzonite/quartz monzodiorite body of Mt Cer was emplaced not later than 21 Ma, whereas the emplacement ages of the Stražanica granodiorite/quartz monzonite and two-mica granites are estimated at around 18 and 16 Ma, respectively. The Mt Cer pluton is similar to the Mt Bukulja pluton, some 80 km southwestwards. Genesis of QMZD cannot be interpreted by fractional crystallization coupled with mixing or assimilation. It is best explained by a convection-diffusion process between mantle-derived minette/leucominette magmas and GDS-like magmas followed by two end-member magma mixing. The composition of GDS rocks suggests that GDS-like magmas could have formed by melting of lower crustal lithologies similar to amphibolite/metabasalts. The geochemistry of TMG is reproduced by an Assimilation/Fractional Crystallization model with a ratio of rate of assimilation to rate of fractional crystallization of 0.4, using the compositions of the least evolved TMG of the Bukulja pluton and adjacent metamorphic rocks as proxies for the parental magma and contaminant, respectively. The origin and evolution of the Mt Cer and adjacent Mt Bukulja plutons provide new constraints on the Tertiary geodynamics of the northern Dinarides-southern Pannonian region. The quartz monzonite/quartz monzodiorite is interpreted as a result of the Oligocene post-collisional Dinaride orogen-collapse, which included a limited lithosphere delamination, small-scale mantle upwelling, and melting of the lower crust. By contrast, the two-mica granite magmas formed through melting in shallower crustal levels during the extensional collapse in the Pannonian area.

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Magmatic epidote and its petrologic significance

Cited by 296 publications

References 0 publications

Geochemistry of the Rio Espinharas hybrid complex, northeastern Brazil

Geochemistry of the Rio Espinharas hybrid complex, northeastern Brazil

Magmatic garnet in the Cordilleran-type Galiléia granitoids of the Araçuaí belt (Brazil): Evidence for crystallization in the lower crust

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

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