tholeiitic series

…the iron-rich group called the tholeiitic series and the iron-poor group called calc-alkalic. The former group is most commonly found along the oceanic ridges and on the ocean floor; the latter group is characteristic of the volcanic regions of the continental margins (convergent, or destructive, plate boundaries; see below Forms…

In Japan a tholeiitic series and a calc-alkalic series sometimes erupt from the same volcano. The former is characterized by lower magnesium, potassium, nickel, chromium, uranium, and thorium and a higher iron:magnesium ratio. Mineralogically, the tholeiitic series characteristically contains pigeonite (a low-calcium monoclinic pyroxene) in the groundmass of…

…former islands: Schouwen en Duiveland, Tholen, Noord-Beveland, Walcheren, Zuid-Beveland, and Sint Philipsland. None of these has preserved a true insular character, all being connected to each other or to Noord-Brabant province inland by dams or bridges.