摘要
The Guinier-Preston zone, which has been found in both lunar and terrestrial orthopyroxenes, is a metastable phase of orthopyroxenes with a wollastonite content～25％ and a new pyroxene space-group symmetry Pbc 21. Its size, distribution, composition and structure may be important indicators of the low-temperature thermal history of orthopyroxene. The ultrastructures of two terrestrial bronzites have been observed under HREM (TEM-100CXII). The size, shape and
