Kerrich, Robert, Manikyamba, Chakravadhanula (2012) Contemporaneous eruption of Nb-enriched basalts – K-adakites – Na-adakites from the 2.7 Ga Penakacherla terrane: implications for subduction zone processes and crustal growth in the eastern Dharwar craton, India. Canadian Journal of Earth Sciences, 49 (4) 615-636 doi:10.1139/e2012-005
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Contemporaneous eruption of Nb-enriched basalts – K-adakites – Na-adakites from the 2.7 Ga Penakacherla terrane: implications for subduction zone processes and crustal growth in the eastern Dharwar craton, India | ||
| Journal | Canadian Journal of Earth Sciences | ||
| Authors | Kerrich, Robert | Author | |
| Manikyamba, Chakravadhanula | Author | ||
| Year | 2012 (April) | Volume | 49 |
| Issue | 4 | ||
| Publisher | Canadian Science Publishing | ||
| DOI | doi:10.1139/e2012-005Search in ResearchGate | ||
| Generate Citation Formats | |||
| Mindat Ref. ID | 484821 | Long-form Identifier | mindat:1:5:484821:3 |
| GUID | 0 | ||
| Full Reference | Kerrich, Robert, Manikyamba, Chakravadhanula (2012) Contemporaneous eruption of Nb-enriched basalts – K-adakites – Na-adakites from the 2.7 Ga Penakacherla terrane: implications for subduction zone processes and crustal growth in the eastern Dharwar craton, India. Canadian Journal of Earth Sciences, 49 (4) 615-636 doi:10.1139/e2012-005 | ||
| Plain Text | Kerrich, Robert, Manikyamba, Chakravadhanula (2012) Contemporaneous eruption of Nb-enriched basalts – K-adakites – Na-adakites from the 2.7 Ga Penakacherla terrane: implications for subduction zone processes and crustal growth in the eastern Dharwar craton, India. Canadian Journal of Earth Sciences, 49 (4) 615-636 doi:10.1139/e2012-005 | ||
| In | (2012, April) Canadian Journal of Earth Sciences Vol. 49 (4) Canadian Science Publishing | ||
| Abstract/Notes | An association of Nb-enriched basalts (NEB), high-MgO andesites (HMA), and flows with adakitic characteristics are interlayered with tholeiitic pillow basalts in the 2.7 Ga Penakacherla greenstone belt of eastern Dharwar craton. Two populations of basalt are present, a high-Mg# Ni (0.65–0.56, 106–52 ppm) and low-Mg# Ni (0.45–0.34, 32–13 ppm) counterpart; Nb spans 6.3–18 ppm relative to “normal” arc tholeiitic basalts, where Nb ∼3 ppm, and hence qualify as NEB. Basalts plot on the low-Ce/Yb trend of intraoceanic arcs, and have fractionated heavy rare-earth elements (HREE) indicative of melting with residual garnet at >90 km. Ratios of Nb/Ta (7.6 ± 0.7), Zr/Hf (44 ± 0.8), and Zr/Sm (27 ± 2.4) are systematically low, high, and similar to respective primitive mantle ratios of 17, 36, and 25, consistent with a mid-ocean ridge basalt-like mantle source in the sub-arc mantle wedge. Intermediate compositions are divided into high-K but low-Na (K2O 1.8–5.3; Na2O 0.5–2.1 wt.%) and low-K but high-Na (K2O 0.10–1.5; Na2O 4.1–5.6 wt.%) populations defining distinct magma series; accordingly, these are termed K-adakitic and Na-adakitic rocks, respectively. The Na-type has SiO2 ≥56 wt.%, MgO <3 wt.%, Mg# ∼0.5, Na2O ≥3.5 wt.%, K2O ≤3 wt.%, Yb ≤1.9 ppm, Cr ≥30 ppm, with slightly lower limits of Al2O3 ≥15 wt.% and La/Yb 7.5–8.2 versus ≥20, thus conforming to most criteria for Na-adakites. NEB are interpreted as melts of mantle wedge hybridized by adakitic melts having residual garnet; and Na-adakites are slab melts of low-Mg basalt in the garnet–amphibolite facies. K-adakitic flows are melts of mafic lower crust, or melts of lower crust delaminated into mantle wedge asthenosphere. | ||
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