HotStuff - Crystal mush dykes as conduits for mineralising fluids in porphyry systems - Lawrence Carter

We are pleased to announce a HotStuff seminar by Lawrence Carter on the topic of: Crystal mush dykes as conduits for mineralising fluids in porphyry systems.

Abstract:

Porphyry-type deposits are the world’s main source of copper and molybdenum, and provide a large proportion of gold and other metals. They form in the upper (ca. 2–5 km deep) parts of large, long-lived magmatic-hydrothermal systems in which mineralising fluids are thought to be derived from mid-to shallow-crustal magma chambers. Magmatic systems are increasingly viewed as consisting of mush with minor and transient lenses of magma, with mush being a variably packed framework of crystals with interstitial melt and magmatic volatile phase (MVP). In this context, questions remain as to the source (mainly depth) and mechanisms of transport and focussing of the vast volumes of fluids required for shallow level porphyry-type mineralisation. Even more problematic is a paucity of first-order textural evidence for the presence of mush in magmatic-hydrothermal systems, including those which host porphyry-type deposits.

Investigating these questions, Lawrence studies cupola zones through which mineralising magmatic-hydrothermal fluids were focused (i.e. the ‘root-zones’ of porphyry deposits). Lawrence integrates field observations of magmatic-hydrothermal textures with micro-scale textural and geochemical studies to evidence the development of fluid pathways and conduits through mush at the magmatic-hydrothermal transition. Lawrence compares these textual observations with geochronological data for magmatic  and hydrothermal events to provide temporal constraints on the duration of mineralising magmatic-hydrothermal fluid flow through crystal mush conduits in porphyry systems. Lawrence suggests that these processes should be considered in all new genetic, exploration and numerical models for porphyry and similar types of magmatic-hydrothermal ore-deposits.