Magma associations in Ediacaran granitoids of the Cachoeirinha-Salgueiro and Alto Pajeu terranes, northeastern Brazil: Forty years of studies

作者：Sial Alcides N^*; Ferreira Valderez P

来源：Journal of South American Earth Sciences, 2016, 68: 113-133.

DOI：10.1016/j.jsames.2015.10.005

• Ediacaran
• Magma association
• Magma transport
• Oxygen isotopes
• Magnetic susceptibility
• Strontium and neodymium isotopes

Granitic magmatism in the Cachoeirinha Salgueiro and Alto Pajeu terranes in the Transversal Zone Domain of the Borborema Province, northeastern Brazil, occurred in three main time intervals: 650-620 Ma, 590-560 Ma and 545-520 Ma. The oldest one is characterized by intrusions of magmatic-epidote (mEp) bearing calc-alkalic (some with trondhjemitic affinities) and high-K calc-alkalic plutons, synkinematic to the main regional foliation, under contractional tectonic regime, and exhibits T-DM < 2.0 Ga and epsilon Nd (0.6 Ga) from -1 to -4, and delta O-18 (zircon) values from 7.1 to 10%(VSMow). O- and Nd-isotope data for the 650-620 Ma group of plutons is compatible with partial fusion of subducted oceanic basaltic crust (mEp-bearing calc-alkalic tonalites/granodiorites, equivalent to adakites). Voluminous intrusions in the 590-560 Ma interval are represented by abundant mEp-free high-K calc-alkalic, peralkalic, ultrapotassic, mEp-bearing high-K calc-alkalic, and less abundant shoshonitic magmas. Nd-model ages for this group of plutons vary from 1.5 to 2.5 Ga and ENd (0.6 Ga) ranges from -8 to -20; delta O-18 (zircon) varies from 6.4 to 7.9%(VSMOW.) Values of delta O-18 (zircon) for the 590-560 Ma old group of plutons coupled with Nd isotope data are compatible with remelting of crustal (negative epsilon Nd, 1.6 to 2.0 Ga old) source rocks. O- and Nd-isotope data for this group of plutons are compatible with underplating of basaltic magma in the base of the lower crust for the high-K calc-alkalic granitoids, coeval to transcurrent movements along sigmoidal shear zones. Intrusion of one shoshonitic (Serrote do Arapua), one calc-alkalic (Riacho do Ico) plutons besides the peralkalic ManaIra-Princeza Isabel dike set have witnessed this transition from contractional to transcurrent movements along shear zones, around 610-600 Ma.

• 出版日期2016-7