Evaluating Mechanisms for the Formation, Propagation and Evolution of Volcanic Rifts and Margins

Lead PI: Dr. W. Roger Buck

Unit Affiliation: Marine and Polar Geophysics, Lamont-Doherty Earth Observatory (LDEO)

May 2017 - April 2019
Inactive
Global
Project Type: Research

DESCRIPTION: Massive volumes of magma poured out and filled in the split during the breakup of the supercontinent Pangea. As much as ten million cubic kilometers of basalt may have erupted in just a few hundred thousand years, and the magma may have triggered the rupture of the continent. Geologists define these areas of massive eruptions as Large Igneous Provinces. The Ethiopian Plateau is an example of a younger volcanic province, while the Palisades on the opposite side of the Hudson River from Manhattan is part of a of a 200-million-year-old volcanic province that stretches from Newfoundland to Brazil. In recent years, scientists have collected data that provide evidence of thick piles of lavas buried just offshore of most rifted continental margins, and as much lava may be offshore as what is estimated from mapping on land. This project is focused on using numerical models to simulate and understand the way magma intrusion and extrusion influence the breakup of continents and the structure of the resulting continental edges. There is growing interest in how these types of magmatic processes affect the generation and preservation of hydrocarbons. The project supports the training of a post-doctoral researcher and a graduate student. The thick sequences of volcanic flows found offshore of most rifted margins, termed Seaward Dipping Reflectors (SDRs), are a defining feature of volcanic margins. However, the formation of these features and the potential contribution of mantle plumes as a source of the lavas that form SDRs remain a topic of controversy. This project considers the large-scale question of whether plumes are consistent with volcanic rift propagation. Observations suggesting that rifts propagate from the distal end of rifts to the central, plume-affected areas has called into question the idea that plumes are needed to initiate volcanic rifts such as those that produced most of the Atlantic margins. The primary hypothesis of this project is that a rapidly evolving pattern of volcanism along a rift can reconcile the plume concept and the observed rift propagation directions. Testing this hypothesis requires consideration of how volcanism is fed along a several thousand kilometer-long volcanic rift. This study uses moderately low-resolution 3-D models of mantle flow and melting to consider how plume material might spread along an incipient rift. The second, and main, component of the study focuses on 2-D cross-sectional models of magmatic rift development. The effect of magma intrusion and volcanism on rift formation and particularly on the development and the rapid subsidence of SDRs will be assessed. Preliminary models produce fast subsidence after SDR formation if the lower crust can flow into a region of stretching crust. The new models will allow quantitative testing of previous conceptual models, particularly those involving lateral variability in the thermal and density structure of an evolving rift during SDR formation.

SPONSOR:

National Science Foundation (NSF)

FUNDED AMOUNT:

$319,977

WEBSITE:

https://www.nsf.gov/awardsearch/showAward?AWD_ID=1654745&HistoricalAwards=false

PUBLICATIONS:

Tian, X. and Buck, W. R.. "Lithospheric thickness of volcanic rifting margins: Constraints from seaward dipping reflectors," Journal of geophysical research. Solid earth, v.124, 2019. Citation details

KEYWORDS

magma seaward dipping reflectors large igneous provinces

THEMES

Earth fundamentals