Open AccessVolcanic‐plutonic connections in a tilted nested caldera complex in Hong Kong
Author(s) -
Sewell Roderick J.,
Tang Denise L. K.,
Campbell S. Diarmad G.
Publication year - 2012
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2011gc003865
Subject(s) - geology , caldera , silicic , volcano , rhyolite , magma chamber , magma , cretaceous , dike , outcrop , geochemistry , volcanic rock , seismology , paleontology
Exceptional exposures of four, precisely dated, Middle Jurassic to Early Cretaceous, silicic volcanic centers and their plutonic equivalents in Hong Kong have provided an excellent opportunity to examine close connections in time and space between magma chambers and their overlying calderas. Here, we describe a ∼14 km crustal section through a collapsed caldera in southeastern Hong Kong where the intracaldera fill suggests that the magmatic discharge was of supereruption scale. The main subvolcanic components that link a magma chamber with surface are revealed by well‐established field relationships, supplemented by high precision geochronology, whole‐rock geochemistry, and geophysical data. Exposures and outcrop patterns reveal kilometer‐scale caldera subsidence and evidence of the simultaneous evacuation of hundreds of cubic kilometers of high‐silica rhyolite magma through dike‐like conduits from a shallow subcrustal reservoir. The resultant volcanotectonic depression, within which is preserved a single cooling unit of massively columnar‐jointed densely welded tuff (High Island tuff), is interpreted to form part of a larger tilted Early Cretaceous nested caldera complex. The High Island eruption signaled the end of a 24 Myr‐period of voluminous, pulsed Middle Jurassic to Early Cretaceous silicic magmatism in the Hong Kong region characterized by four discrete ignimbrite ‘flare‐ups’.