Volcanic Composition

In Lombok, Rinjani volcano lies just about three hundred kilometres (188 mi) north of the Sunda Trench (also referred to as Java trench) and is set about a hundred and seventy kilometres (110 mi) higher than the active north dipping Benioff zone. Supported the composition of andesites that have terribly low metal concentrations and low Mg/Mg+Fe it’s prompt that the Rinjani suite is of mantle origin, however that every one the andesites and dacites moreover as several of the basalts have most likely been changed by fragmental crystallization processes. It’s finished that the Rinjani calc-alkaline suite, that in several respects is typical of the many suites erupted by circum-pacific volcanoes, most likely originated by partial melting of the peridotite mantle-wedge superimposed the active Benioff Zone at a lower place Lombok Island.

The Pleistocene-Recent calcalkaline suite from the active volcano, Rinjani consists of a various vary of lavas. These include: ankaramite, high-Al volcanic rock, andesite, high-K igneous rock and volcanic rock. Sr-isotopic and geochemical constraints counsel that this suite was derived from the sub-arc mantle. Geochemical models counsel that fragmental crystallization is a very important method within the suite’s differentiation, though the series: ankaramite-high-Al basalt-andesite-dacite doesn’t represent a endlessly evolving spectrum of liquids.