K-Ar (40Ar/39Ar) Geochronology of Ultrahigh Pressure Rocks

摘要: Although 40Ar/39Ar dating studies have been successful in setting age constraints on many ultrahigh pressure (UHP) occurrences world-wide, argon isotopic data from UHP rocks occasion proven difficult to interpret terms of cooling and exhumation ages. One principal reason is that the closure behavior common, high-K rock-forming minerals (phengite, phlogopite, biotite) poorly understood contexts, with variations occurring at scale a single outcrop—or even mineral—that are often relate actual pressure-temperature-time path experienced by these rocks. The second can be contaminated excess 40Ar, commonly resulting apparent ages well above those measured other systems same (e.g., Rb/Sr, U/Pb, Sm/Nd). After reviewing number structural-physical aspects bearing transport phenomena UHP, this chapter outlines main crystal-related compositional, structural, effects influential record micas. Other important argon-fluid-mineral partition then explored connection their relevance for incorporation mechanisms 40Ar