Magmatic flow paths and palaeomagnetism of the Miocene Stoddard Mountain laccolith, Iron Axis region, Southwestern Utah, USA

Abstract

The Stoddard Mountain laccolith is part of a complex of Early Miocene laccoliths intruded along the western edge of the Colorado Plateau in the Iron Axis region of Southwestern Utah. Most Colorado Plateau laccoliths (e.g. Henry and La Sal Mountains) are considered to be fed by a central axial feeder system. However, detailed mapping in the Iron Axis region suggests that the Stoddard Mountain laccolith was fed laterally from the west. Structural and field data suggest the quartz monzonitic magma initially migrated laterally eastward at ∼1 km depth as a sill before spreading laterally north-south where it inflated to ∼1–1.5 km thickness. To test the model of a lateral feeder system, data were collected from 32 palaeomagnetic sites and 76 AMS stations (763 accepted specimens) sampled over the ∼54 km2 exposed part of the N-S oval-shaped laccolith. The in situ AMS fabrics, inferred to correlate with magmatic fabrics, typically show NE trending lineations in the north and S-SE trending lineations in the south part of the intrusion. The palaeomagnetic data are interpreted to indicate a very minimal amount of post-emplacement deformation of the intrusion. The overall lack of westerly-directed and steep magnetic lineations argues against emplacement via a central axial feeder system.

Distinguishing diapirs from inflated plutons: an integrated rock magnetic fabric and structural study on the Roundstone Pluton, western Ireland

“…These findings are consistent with those of several other studies on granitoids of similar grain size (e.g. Ferré et al 1999;Petronis et al 2004;Martins et al 2011).…”

“…9b). Lateral emplacement of magma initially occurred as a thin sheet that extended to the full diameter of the intrusion to form a disc shape prior to vertical inflation (Pollard & Johnson 1973;Corry 1988;Petronis et al 2004). Early emplacement was driven by excess magma pressure and was facilitated by ductile up-doming of the bounding roof that accommodated pluton inflation (Fig.…”

The emplacement of the Palaeogene Mourne Granite Centres, Northern Ireland: new results from the Western Mourne Centre

“…The fabric pattern that Stevenson et al (2007b) revealed did not provide any evidence of vertical magma flow consistent with a ring-dyke style feeder. Instead, AMS data revealed lateral magma flow directed NNE indicated by northward divergence of the AMS lineation pattern (see Petronis et al 2004). Stevenson et al (2007b) acknowledged, however, that the inflow may have alternatively been from the eastern (or northeastern) margin, possibly from an unexposed ring-dyke style feeder, or from subjacent dykes.…”

Emplacement history of the Trosky basanitic volcano (Czech Republic): paleomagnetic, rock magnetic, petrologic, and anisotropy of magnetic susceptibility evidence for lingering growth of a monogenetic volcano

“…Moreover, to a certain extent, it provides an estimate of the amount of strain (Borradaile and Henry 1997;Bouchez 1997Bouchez , 2000. Even in weakly anisotropic material, it is now widely accepted that the magnetic lineations and foliations potentially reflect the magmatic fabric and can provide information on magma migration, flow geometries, and regional strain (King 1966;Owens and Bamford 1976;Hrouda 1982;Rochette 1987;Rochette et al 1992;Tarling and Hrouda 1993;Bouchez 1997;Borradaile and Henry 1997;Dietl 1999;Sant'Ovaia et al 2000;Petronis et al 2004Petronis et al , 2009Petronis et al , 2013Horsman et al 2005;Sidman et al 2005;Žák et al 2005O'Driscoll et al 2006;Stevenson et al 2007;Kratinová et al 2010). In the following, we consider the possible driving mechanisms that formed the fabrics revealed by AMS data from the Trosky volcano.…”