Linear volcanic segments in the Sunda Arc, Indonesia: Implications for arc lithosphere control upon volcano distribution
Abstract
The overall curvature of many subduction zones is immediately apparent and the term island arc betrays the common assumption that subduction zone magmatism occurs in curved zones. This assumption can be expressed by approximating island arcs as segments of small circles on the surface of a sphere. Such treatments predict that the location of arc volcanoes is related to their vertical separation from the slab (in fact, the depth to seismicity in the slab) and require that the primary control on the locus of magmatism lies either within the subducted slab or the mantle wedge that separates the subducted and overriding lithospheric plates. The concept of curved arcs ignores longstanding observations that magmatism in many subduction systems occurs as segments of linearly arranged volcanic centres. Further evidence for this distribution comes from the close relationship between magmatism and large scale, arc-parallel fabrics in some arcs. Similarly, exposures of deep arc crust or mantle often reveal elongation of magmatic intrusions sub-parallel to the inferred trend of the arc. The Sunda Arc forms the Indonesian islands from Sumatra to Alor and provides an important test for models of volcano distribution for several reasons. First, Sunda has hosted abundant historic volcanic activity. Second, with the notable exception of Krakatau, every volcano in the arc is subaerial from base to cone and, therefore, can be readily identified where there is a suitable extent of local mapping that can be used to ground-truth satellite imagery. Third, there are significant changes in the stress regime along the length of the arc, allowing the influence of the upper plate to be evaluated by comparison of different arc segments. Finally, much of the Sunda Arc has proved difficult to accommodate in models that try to relate volcano distribution to the depth to the subducted slab. We apply an objective line-fitting protocol; the Hough Transform, to explore the distribution of volcanoes in the central Sunda Arc from Java to central Flores. We focus on this section because of the complicating influences of the Great Sumatran Fault, further to the west, and the collision between the arc and Australian continental lithosphere, to the east of central Flores. Volcano distribution in the central Sunda Arc is best described as linear segments, rather than as small circles. We conclude that the stress field in the Sunda Arc lithosphere is the primary control on the distribution of its volcanoes. Changes in the location and petrographic/geochemical characteristics in magmatism from initiation, in the late-Plio-Pleistocene, until the present day can also be attributed to the evolving stress in the upper plate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.T51D2627M
- Keywords:
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- 8164 TECTONOPHYSICS / Stresses: crust and lithosphere;
- 8170 TECTONOPHYSICS / Subduction zone processes;
- 8185 TECTONOPHYSICS / Volcanic arcs;
- 8413 VOLCANOLOGY / Subduction zone processes