925 resultados para Solomon, Alisa
Resumo:
The paper is based on new results of melt inclusion studies in minerals. Physicochemical and geochemical parameters of plateau basalt magmatic systems of the Siberian Platform and Ontong Java Plateau (Pacific Ocean) have been established. The studied melts are enriched in Fe. That differs them from magmatic melts of mid-ocean ridges (MOR). A comparative analysis of data on inclusions has shown a similarity of continental and oceanic plateau basalt magmatic systems. They considerably differ from those of MOR and intraplate oceanic islands. Crystallization of oceanic plateau basalts took place at lower temperatures and pressures as compared with similar rocks of the Siberian Platform. The data on inclusions evidence that the melts of the Siberian Platform and the Malaita Island underwent a serious evolution in contrast to magmas of the Nauru Basin that have more stable geochemical parameters. The most fractionated low-temperature high-Fe magmas with elevated contents of trace and rare-earth elements occur in the Malaita Island (Ontong Java Plateau) magmatic system.
Resumo:
The relative abundance of warm-water Discoaster brouweri vs. cool-water Coccolithus pelagicus provides a useful proxy for interpreting Pliocene surface water temperature trends at Ocean Drilling Program Site 1115 (Solomon Sea). Surface waters were mostly warm during the early Pliocene with a slightly cooler interval centered on 4.5 Ma. A more pronounced cool interval occurred at ~3.2 Ma. The early and mid-Pliocene cool periods may reflect Antarctic glacial growth. A mid-Pliocene warm interval occurred from ~3.1 to 2.8 Ma. Temperature began to decline beginning ~2.7 Ma, marking the onset of Northern Hemisphere glaciation. This long-term decline in surface water temperature is interrupted by a brief warming event at ~2.3 Ma.
