摘要
呈岩盆状产出的矾山铁磷矿床含矿岩体,属层状超镁铁岩系列,其中各岩相带均为层状结构,而且辉石岩带和黑云辉石岩带又大致以剖面中心的伟晶正长黑云辉石岩为对称构成有规律的韵律层。本文讨论了韵律层结构的成因,认为韵律层实际上是按一定间隔形成黑云辉石岩造成的。黑云辉石岩是在岩浆结晶过程中的残余流体交代先成辉石岩的产物。文中按黑云母内的铁镁比值计算了此交代反应的计量系数,由实测地质数据按质量守恒方程得到了在各岩相带两相邻界面上的交代流体中SiO_(2)和CaO的含量差。由于此含量差的有规律变化,使交代作用间歇进行,因而有规律地出现黑云辉石岩,于是造成韵律层结构。
The Fanshan ore-bearing rocks are characterized by a series of ultramafic rock zones showing rhythmic layered structures.Alternating diopside-rock and biotite-bearing diopside-rock zones occur almost symmetrically above and below the central zone of dominant orthoclase-and biotite-bearing diopside-rocks of the ultramafic"succession"(Table 1).In this paper the genesis of the layered structure is discussed.The author deems that the layered structure is essentiatlly resulted from the formation of biotite-bearing diopside-rocks at certain intervals through the replacement of the original,early-formed diopside-rocks by the residual fluid late in the magmatic crystallization process.The stoichiometric coefficients of metasomatic reactions are calculated by usingΣFe/(ΣFe+Mg)of biotite.The differences of SiO_(2-)and CaO_(2-)contents in the metasomatic fluid at two adjacent boundaries of each rock zone are obtained on the basis of mass balance equation for the field observation data.Because of the regular change of such content differences,metasomatic process progressed intermittently and biotite-bearing diopside-rocks formed at rather regular intervals,thus resulting in the layered structure.
作者
江培谟
Jiang Peimo(Deparment of Geology,Beijing University)
出处
《地质学报》
1985年第1期33-46,共14页
Acta Geologica Sinica
