Diamond from the dabie shan metamorphic rocks and its implication for tectonic setting

Area of Science:

• Geology
• Mineralogy
• Petrology

Background:

• Diamond occurrences in ultrahigh-pressure metamorphic rocks.
• Dabie Shan, China as a key geological site.

Purpose of the Study:

• To investigate the origin and conditions of diamond formation in Dabie Shan metamorphic rocks.
• To understand the geological processes involved in ultrahigh-pressure metamorphism.

Main Methods:

• Analysis of mineral assemblages (diamond, coesite, jadeite).
• Geological mapping and petrographic studies.
• Thermodynamic modeling of diamond stability fields.

Main Results:

• Diamond found in eclogite, garnet-pyroxenite, and jadeitite.
• Diamonds co-exist with coesite and jadeite, indicating extreme pressures.
• Diamonds are primarily euhedral inclusions in garnets, ranging from 10 to 700 micrometers.

Conclusions:

• Dabie Shan diamonds are products of early Mesozoic ultrahigh-pressure metamorphism (>4.0 GPa, 900°C).
• Metamorphism occurred in the underthrust basement of the Yangtze continental plate.
• Isotopic data suggest a crustal origin for these diamondiferous rocks.