S U M M A R Y An assumption of isothermal and static asthenosphere as the normal state of sublithospheric mantle, as commonly employed in studies of terrestrial magmatism, may be physically implausible for a system cooled from above. The growth of an unstable thermal boundary layer at the base of the lithosphere can lead to small-scale convection, so asthenosphere is expected to be usually conv...

Magmatism during early Basin and Range extension in Trans-Pecos Texas consisted of widespread but volumetrically minor alkali basalts (24-17 Ma), an alkalic mafic to intermediate composition stratovolcano (28-27 Ma), and a dominantly rhyolitic, possibly bimodal, caldera complex in adjacent Chihuahua (3128 Ma). This magmatism contrasted sharply with the much more voluminous and compositionally m...

Tertiary±Recent magmatism in the Kenya Rift Valley was initiated c. 35Ma, in the northern part of Kenya. Initiation of magmatism then migrated southwards, reaching northern Tanzania by 5±8Ma. This progressionwas accompaniedby a change in the nature of the lithosphere, from rocks of the Panafrican Mozambique mobile belt through reworked craton margin to rigid, Archaean craton. Magma volumes and ...

Mid-ocean ridge magmatism is driven by seafloor spreading and decompression melting of the upper mantle. Melt production is apparently modulated by glacial-interglacial changes in sea level, raising the possibility that magmatic flux acts as a negative feedback on ice-sheet size. The timing of melt variability is poorly constrained, however, precluding a clear link between ridge magmatism and P...

The intrusive age ranges of Linglong, Guojialing, Weideshan, and Laoshan granites in the Jiaodong Peninsula are 155–154 Ma, 131–130 118–111 116 respectively. Together with Shidao granite (227–200 Ma), five phases magmatism can be classified by time, all which have different degrees gold polymetallic mineralization. type evolved from A–, S–type to I–, A–type Late Triassic Early Cretaceous, thus ...

Tectonic collision between South America and Panama began at 23–25 Ma. The collision is signifi cant because it ultimately led to development of the Panamanian Isthmus, which in turn had wide-ranging oceanic, climatic, biologic, and tectonic implications. Within the Panama Canal Zone, volcanic activity transitioned from hydrous mantle-wedge−derived arc magmatism to localized extensional arc mag...

The Neoproterozoic shoshonitic and mildly alkaline bimodal volcanism of Southernmost Brazil is represented by rock assemblages associated to sedimentary successions, deposited in strike-slip basins formed at the post-collisional stages of the Brasilian/Pan-African orogenic cycle. The best-preserved volcano sedimentary associations occur in the Camaquã and Campo Alegre Basins, respectively in th...