对地层学中“岩组”含义的商榷

DISCUSSION ON MEANING OF STRATIGRAPHIC "MIXED FORMATION

建议把岩组界定为构造变形强度上介于组与杂岩之间的过渡性地层类型及划分这类地层的基本单元。组是原岩组构保存良好的地层类型,即这类地层的结构构造主要是沉积构造、火山岩原生构造。岩组的结构构造则主要是后期变形变质过程中形成的劈理、片理等构造面理,是由构造置换作用形成的次生结构构造。岩组和杂岩的区别在于:杂岩的构造变形和变质作用更强烈,原生沉积单层被肢解.不同层位的地层发生了强烈的构造混合并常伴有同构造期或（和）后期的岩浆作用的改造;岩组内部及岩组之间则依然保存了明确的岩性和构造分界,各自保持着相对的独立性和连续性,具有一定的延展范围。提出了界定岩组的具体标准并认为岩组的英语译名以“Mixed Formation”或创名为“Mixformation”较合适。

Mixed Formation' suggested here is the basic stratigraphic unit with structural deformation between 'formation' and 'complex'. 'Formation' should be the stratigraphic unit with well-reserved primary fabric, including sedimentary and volcano-sedimentary structures. Fabric in 'mixed formation' are mainly secondary textures and structures (such as cleavage and schistosity) formed during deformation and metamorphic process, which is different from 'complexes' with stronger structural deformation and metamorphism. Primary sedimentary bedding in 'complexes' should have been broken up with different beds tectonically commixed and usually reconstructed by synkinematic or subsequent intrusions. Independent but continuous diagenetic and structural boundaries can be found inside and between the 'Mixed Formation'.