Concentrically zoned skarns on Mt. San Gorgonio have been studied in detail from the point of view of field and petrographic relations. The skarns are mineralized blocks of marble of the Precambrian San Gorgonio Igneous-Metamorphic Complex, which are within the contact zone between the Complex and the Middle Jurassic Cactus Quartz Monzonite. They consist of cores of calcite-forsterite-diopside marble, surrounded by concentric zones of diopside, actinolite + epidote + calcite + quartz, epidote + garnet + calcite + quartz, and scapolite + calcite + quartz. The genesis of the skarns involved three steps. (1) Regional metamorphism formed tremolite and forsterite from calcite, dolomite, and quartz.(2) The intrusion of the quartz monzonite stabilized diopside + forsterite relative to tremolite + calcite. Reaction between quartz monzonite and marble resulted in the formation of a zone of diopside + wollastonite and a zone of sodic scapolite, by the diffusion of Ca, Mg, and Si across the original contact. Components rejected from this zone formed ferroan diopside in the scapolite zone and in the quartz monzonite, and altered the scapolite to a more calcic form. This process involved a net volume loss of 56.6 percent. (3) Infiltration of fluids, possibly of magmatic origin, formed epidote and garnet from scapolite, and actinolite from diopside.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.