Geochemistry of the Rio Espinharas hybrid complex, northeastern Brazil

Abstract

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

Experimental anatexis, fluorine geochemistry and lead-isotope constraints on granite petrogenesis in the Seridó Belt, Borborema Province, northeastern Brazil

“…The high-K calc-alkaline plutons are formed by mafic to intermediate rocks coexisting with abundant felsic rocks. These rocks show remarkable mingling and mixing features that are characteristic of the Borborema Province magmatism (Ferreira et al, 1998;Archanjo et al, 1992;Galindo et al, 1993;Jardim de Sá, 1994;Jardim de Sá et al, 1999;Nascimento et al, 2000;Vauchez, 1995, 2000;Campos et al, 2002;Hollanda et al, 2003;Van Schmus et al, 2003). U-Pb zircon ages indicate a first intrusive episode at 590 Ma with the emplacement of the mafic to intermediate rocks of the Tororó pluton.…”

Geochemical and isotopic evidence for magma mixing/mingling in the Marshenan intrusion: Implications for juvenile crust in the Urumieh–Dokhtar Magmatic Arc, Central Iran

“…Disequilibrium textures, such as skeletal morphology of amphibole, is indicative of rapid growth, consistent with rapid fluctuations in magma conditions and mixing and (or) mingling processes (Campos, Neiva, & Nardi, 2002). Also, the host rocks often contain small clots of biotite and amphibole, titanite with sometimes a nucleus of residual pyroxene suggest magma mixing and (or) mingling (Didier, 1987).…”

Nyílt rendszerű magmás folyamatok: magmakeveredés, kristálycsere és kumulátum-recirkuláció nyomai a Ditrói alkáli masszívumban (Orotva, Románia)

“…FROST & MAHOOD (1987) az elegyedést két eltérő kémiai összetételű magmának a keveredéseként értelmezik, amely során egy új, homogén, hibrid magma jön létre. Az elegyedés eredményét tehát két magma "kombinációjaként" lehet értelmezni (MICHEL et al 2016), ahol a létrejövő hibrid magma (vagy magmák) homogén(ek) és köztes geokémiai összetételt, a keveredő szélsőtagok között lineáris trendet mutat(nak) (CAMPOS et al 2002).…”