The Tambo Grande deposits are in a very similar setting to the Santa Elena occurrence, and given that both are in what appears to be an oceanic backarc
setting, this district may be a model for Santa Elena.
Also, this mountain chain may represent a generally non-extended backarc
to the continental arc of the Sierra Madre Occidental (Ortega-Gutierrez et al.
The author employs several collision models to support his findings and to explain why the traditional model of a backarc
shortening above an eastwardly dipping subduction zone does not fit current data.
Deep sea research in subduction zones, spreading centres and backarc
However, the ascent of such small volumes of melt is mechanically problematic (see Murphy 2006) and so alkalic magmas in arc settings tend to be restricted to specialized settings, such as local rift zones within the arc or backarc region.
Shoshonite occurs in association with calc--alkaline volcanism in intra-arc rift settings, in intra-oceanic island arcs and backarc basins, (Sun and Stern 2001; Adams et al.
2]O on crystallization of mid-ocean ridge and backarc
6) the backarc region behind the volcanic chain that may contain marginal basins or inactive ancient arcs.
A low-stress subduction zone exhibits a small accretionary wedge, few large earthquakes, igneous rocks with a narrow basaltic compositional range, a steeply dipping down-going slab, and a well-developed backarc basin.
However, the epithermal deposits east of PNG, in Fiji and in the Coromandel goldfield are also associated with felsic to mafic alkalic rocks and normal faulting indicating an extensional tectonic regime, probably in a backarc
or intra-arc setting.
Chapters were taken from the Ridge 2000-InterRidge Theoretical Institute, "Interactions among Physical, Chemical, Biological, and Geological Processes in Backarc
Spreading Systems," held on Jeju Island, South Korea, in May of 2004.
There may be several mechanisms responsible for backarc
extension, but the currently popular model is the roll-back model (Dewey 1980).