Evolution of Metamorphic Belts

TLDR

Metamorphic facies in regional metamorphism are classified into five pressure-based categories, and in the circum-Pacific region, side‑by‑side belts of low‑ and high‑pressure facies run parallel, with the high‑pressure belt on the Pacific side, suggesting they formed in distinct orogenic phases. The study discusses the origins of these metamorphic belts and briefly examines contact metamorphism facies series. Higher‑pressure regional metamorphism occurred later in geological history.

Abstract

The metamorphic facies series in regional metamorphism may be classified into the following categories according to an order of increasing rock pressure: (1) andalusite-sillimanite type, (2) low-pressure intermediate group, (3) kyanite-sillimanite type, (4) high-pressure intermediate group, and (5) jadeite-glaucophane type. In Japan and other parts of the circum-Pacific region, a metamorphic belt of the andalusite-sillimanite type and/or low-pressure intermediate group and another metamorphic belt of the jadeite-glaucophane type and/or high-pressure intermediate group run side by side, forming a pair. The latter belt is always on the Pacific Ocean side. They were probably formed in different phases of the same cycle of orogeny. Their origin is discussed. Regional metamorphism under higher rock pressures appears to have taken place in later geological times. The metamorphic facies series of contact metamorphism are briefly discussed.