Paleoproterozoic juvenile magmatism within the northeastern sector of the
S~ao Francisco paleocontinent: Insights from the shoshonitic high Ba–Sr
Montezuma granitoids
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Abstract
New, integrated petrographic, mineral chemistry, whole rock geochemical, zircon and titanite U–Pb geochronology,
and zircon Hf isotopic data from the Montezuma granitoids, as well as new geochemical results for its host
rocks represented by the Corrego Tingui Complex, provides new insights into the late- to post-collisional evolution
of the northeastern S~ao Francisco paleocontinent. U–Pb zircon dates from the Montezuma granitoids spread along
the Concordia between ca. 2.2 Ga to 1.8 Ga and comprise distinct groups. Group I have crystallization ages between
ca. 2.15 Ga and 2.05 Ga and are interpreted as inherited grains. Group II zircon dates vary from 2.04 Ga to
1.9 Ga and corresponds to the crystallization of the Montezuma granitoids, which were constrained at ca. 2.03 Ga
by the titanite U–Pb age. Inverse age zoning is common within the ca. 1.8 Ga Group III zircon ages, being related
to fluid isotopic re-setting during the Espinhaco rifiting event. Zircon εHf(t) analysis show dominantly positive
values for both Group I (4 to þ9) and II (3 to þ8) zircons and TDM2 model ages of 2.7–2.1 Ga and 2.5–1.95 Ga,
respectively. Geochemically, the Montezuma granitoids are weakly peraluminous to metaluminous magnesian
granitoids, enriched in LILES and LREE, with high to moderate Mg# and depleted in some of the HFSE. Their
lithochemical signature, added to the juvenile signature of both inherited and crystallized zircons, allowed its
classification as a shoshonitic high Ba–Sr granitoid related to a late- to post-collisional lithosphere delamination
followed by asthenospheric upwelling. In this scenario, the partial melting of the lithospheric mantle interacted
with the roots of an accreted juvenile intra-oceanic arc, being these hybrid magma interpreted as the source of the
Montezuma granitoids. The Corrego Tinguí Complex host rocks are akin to a syn- to late-collisional volcanic arc
granitoids originated from the partial melting of ancient crustal rocks. The results presented in this study have
revealed the occurrence of juvenile rocks, probably related to an island arc environment, that are exotic in
relation to the Paleo- to Neoarchean crust from the S~ao Francisco paleocontinent’s core.
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