Report

Sombrero Uplift Above the Altiplano-Puna Magma Body: Evidence of a Ballooning Mid-Crustal Diapir

Science  12 Oct 2012:
Vol. 338, Issue 6104, pp. 250-252
DOI: 10.1126/science.1226358

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Rise and Subside

Earth's surface tends to deform as magmatic fluids rise toward the surface from below, usually manifesting itself in uplift of continental crust. Fialko and Pearse (p. 250; see the Perspective by Brooks), however, show that subsidence, or widespread sinking, accompanies uplift when magma rises. Satellite measurements reveal that the massive Altipano-Puna magma body in the central Andes balloons upward, causing subsidence around the region of uplift, resembling a sombrero. Melting of surrounding rocks as the magma rises likely withdraws material and causes the subsidence.

Abstract

The Altiplano-Puna ultralow-velocity zone in the central Andes, South America, is the largest active magma body in Earth’s continental crust. Space geodetic observations reported an uplift in the Altiplano-Puna proper at a rate of ~10 mm/year; however, the nature of the inferred inflation source has been uncertain. We present data showing that the uplift has persisted at a nearly constant rate over the past two decades, and is surrounded by a broad zone of subsidence. We show that the ongoing uplift and peripheral subsidence may result from a large mid-crustal diapir fed by partial melt from the Altiplano-Puna Magma Body.

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