新元古代帽碳酸盐岩中帐篷状构造的成因

帐篷构造是碳酸盐岩中的一种特殊沉积组构,因其倒“V”字形形态类似于帐篷(tepee)而得名,被认为是一种无成因意义的沉积组构。传统的帐篷构造在海相至陆相碳酸盐岩中都有发育,形态和胶结物的不同反映了沉积环境的变化,其成因为裂隙填充的胶结物结晶膨胀导致层面突起变形。新元古代帽碳酸盐岩中广泛发育有倒“V”字形的类似构造,但由于形态和成因上都和传统的帐篷构造有所区别,被称为“帐篷状构造”(te-pee-likestructure)。目前其成因解释主要有:“巨风暴潮波痕”、“甲烷气体渗漏”、“地下水侵位”和“晶体结晶”的假说。由于帐篷状构造的形成过程与机制和帽碳酸盐岩的成因密切相关,对帐篷状构造的进一步研究必将帮助我们对新元古代冰期结束机制的理解。

The formation of tepee-like structure in Neoproterozoic cap carbonate

Tepee structure, which is defined for its inverted “V” shape, is a special structure that is mainly found in submarine hardgrounds, peritidal, lacustrine and caliche carbonate sediments. It was proposed to be non-genetic, but its shape and cement reflects different environments. The formation of tepee structures was interpreted to be the result of an expansive force of crystallization of cement, which infilled the fractures of the carbonate crust. In response to this force, the crust bowed up and formed the inverted “V” shape. This special inverted “V” shape also usually and widely occurred in the Neoproterozoic cap carbonates. It was described as a tepee-like structure for its shape, but its forming mechanisms are different from tepee structure. The interpretation of the tepee-like structures in Neoproterozoic cap carbonates will affect the explanation of Neoproterozoic deglaciation. Therefore many different hypotheses, such as “Giant wave ripples”, “Methane seep”, “Underground water upwell” and “Cement crystallization” were proposed to interpret “tepee-like” structures.