Successive granitic magma pulses from heterogeneous source, emplaced in medium to deep crust: The case of The Parnamirim Batholith (Brazil)

• Published in: Lithos Vol. 442-443; p. 107061
• Main Authors: Neves, C.H.S., Ferreira, V.P., Sial, A.N., Lima, B.T.A., Ardila, D.H., Neves, S.P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2023
• Subjects: Crustal reworking; Inherited heterogeneity; Multiple magma pluses; Peraluminous granites; Inherited heterogeneity; Crustal reworking; Multiple magma pluses; Peraluminous granites
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2023.107061

The Parnamirim granitic batholith in the Central Domain of the Borborema Province, in northeastern Brazil, is an elongated horn-shaped intruded in the area where the Pernambuco and Parnamirim shear zones meet each other. The batholith is composed of low to highly felsic peraluminous syenogranite to monzogranite carrying primary biotite and muscovite, and a wide range of accessory minerals (allanite, monazite, apatite, ilmenite, magnetite, zircon and rutile). The presence of magnetite imparts variable magnetic susceptibility, which varies from 0.04 to 3.6 (mSI). The batholith has A/CNK >1.1, SiO2 content from 68.13 to 74.18 wt% and near linear correlations with negative trends for most major and trace elements (Al2O3, Fe2O3T, CaO, TiO2, P2O5, Zr, Ba and Sr relative to SiO2). It is exhibits low Rb/Sr ratio (< 2), is enriched in light rare earth elements and large ion lithophile elements. Shows high LaN/YbN (avg.111), and Eu (low to almost absent), Nb, Sr, P, Ti and Ta negative anomalies. The 87Sr/86Sr(0,6 Ga) ratios vary from 0.7107 to 0.7165 and εNd(0,6 Ga) values range from −23 to −20. The TDMNd age values (2.7 to 2.0 Ga), are similar to the UPb ages of the inherited zircon cores, and to ages of nearby Archean-to-Paleoproterozoic country rocks, interpreted as possible sources for the parental magma. The petrological model that more satisfactorily explains the batholith variations involves magma generation by melting, in pulses or batches, occurred by fluid-absent biotite breakdown. Three main intrusion pulses, well-marked in gammaspectrometric and magnetometric geophysical images, were responsible for the batholith construction at mid- to deep- crustal level (>3.5 kbar). These pulses bear some chemical, isotopic and and mineralogical differences. The first pulse has higher SiO2, Rb/Sr and 87Sr/86Sr(0.6 Ga) values and lower Zr saturation temperature than the other two pulses which, in part are chemically and mineralogically similar to each other and partially coeval. After magma extraction, that the processes of differentiation (e.g. fractional crystallization and magma mixing) did not play a significant role in the magma evolution. The generation of this batholith results from a crustal reworking event (600–590 Ma) in the Central Domain of the Borborema Province, during the Brasiliano-Pan African Orogeny. •Large variations of mineralogy, chemistry and isotopes associated with magma source.•Magma pulses are found to be generated from melting of a heterogeneous source.•Building of granite plutons from the successive addition of multiple pulses of magma.•Peraluminous melt generated during crustal reworking in Brasiliano-Pan-African Orogeny.