Nd, Sr and O isotopic study of the petrogenesis of two syntectonic members of the New Hampshire Plutonic Series

Article Abstract:

Nd, Sr and O isotopic analysis of metasedimentary rocks of the Central Maine Terrane (CMT) and the Bronson Hill Anticlinorium (BHA) reveals the petrogenetic evolution of the Bethlehem Gneiss (BG) and the Kinsman Quartz Monzonite (KQM) of the New Hampshire Plutonic Series. Heterogeneity in initial isotopic compositions and low percentage of mantle-derived component in both BG and KQM suggests mixing of many crustal source rocks. Anatexis of BHA and CMT metasedimentaries, due to crustal thickening during the Acadian orogeny, resulted in simultaneous production of the BG and KQM magmas.

Observations, New Hampshire, Isotopes, Intrusions (Geology)

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Petrogenesis of lavas from the AMAR Valley and Narrowgate region of the FAMOUS Valley, 36 degree-37 degree N on the Mid-Atlantic Ridge

Article Abstract:

Sr and Nd isotopic analysis of basaltic lavas from AMAR Valley and Narrowgate region of the FAMOUS Valley on the Mid-Atlantic Ridge categorizes the lavas into two isotopically homogeneous groups. The aphyric Group II has low 87Sr/86Sr and 143Nd/144Nd, while it is the opposite for the plagioclase phyric Group I. Magmas for the early Group II and the subsequent Group I lavas resulted from multi-stage decompressional melting of progressively depleted spinel-lherzolite. Polybaric equilibrium crystallization of the primary magmas followed after sedimentation.

Radioisotopes, Geology, Radioisotopes in geology, Mid-Atlantic Ridge Rift Valley

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Petrogenesis of basalt-comendite and basalt-pantellerite suites, Terceira, Azores, and some implications for the origin of ocean-island rhyolites

Article Abstract:

The petrogenesis modeling of the recent lava of eruptions in Santa Barbara and Pico Alto volcanoes reflect that there are two separate magnetic systems active on Terceira, where one originates from the off-rift basalts and the other from the rift basalts. The off-rift suite suffer a high-pressure fractionation at the early stage, but the rift suite originates from a low pressure effect. The presence of a compositional gap in the suite is due to the relative incapability of eruption of the intermediate composition magma.

Analysis

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