Reactions between natural serpentinite and quartz under hydrothermal conditions. (1) On synthesis of diopside fiber under hydrothermal condition.

Abstract

Hydrothermal experiments in the system MgO–SiO2–H2O were carried out with the use of natural serpentinite as starting materials without crushing. The serpentinite specimen was prepared as a prismatic form of about 4 mm × 4 mm × 20 mm in size. A serpentinite prism was put into a silver capsule together with fine quartz powder and distilled water. Both sides of the capsule were sealed by welding. All experimental runs were made at 1,000 bars in pressure and at 360°C, 450°C, 495°C and 540°C in temperature. The duration times for maintaining constant temperature were from 16 to 1,000 hours. At temperatures above 450°C, in most experiments many white fibrous diopside crystals grew on surface of the serpentinite specimen. A talc layer was formed at the marginal part of serpentinite specimen, its thickness varied from 0 to 50 μm through all experiments. At temperatures below 360°C, serpentine minerals were preserved in the inner part of the specimen, but at temperatures above 450°C, olivine crystals were formed. These reaction processes were discussed.