摘要
松辽盆地白垩系砂岩以长石岩屑砂岩和岩屑长石砂岩为特征。砂岩中发育长石碎屑、岩屑等不稳定组分,而且随着埋藏深度加深(成岩作用加强)钾长石逐渐减少并最终在2700m以下消失。斜长石碎屑中钠长石组分逐渐增多,钙长石组分逐渐减少,最终形成纯钠端元的钠长石。在成岩过程中长石碎屑的钠长石化主要有3种方式:①由离子交代作用导致长石碎屑的钠长石化;②长石碎屑边缘钠长石次生生长;③与长石碎屑溶解伴生的新生钠长石作用。结合热动力学平衡原理分析,斜长石的钠长石化基本不受成岩温度和压力的制约,而钾长石的钠长石化需要较高的成岩温度和压力作用才能进行。因此,斜长石的钠长石化可见于成岩早期,而钾长石的钠长石化只发生于成岩晚期。
The main types of clastic sandstones are feldspathic litharenite and lithic arkose in the Cretaceous of the Songliao basin. There are many unstable components containing detrital feldspar, lithic fragments and so on. Content of potash feldspar decreases with increasing burial depth increases (increasing diagenesis) and gradually disappears below a depth of 2700 m in detrital feldspar of sandstone. The albite component increases while anorthic component decreases in detrital plagioclase. The plagioclase turned into an end - member component of albite. In the diagenic process, three types of albitization are determined; (1) albitization of metasomatism by means of cation exchange in detrital feldspar; (2) secondary growth of albite on the original detrital feldspar; (3) albite crystallization with detrital feldspar solution. Analysis based on the equilibrium activity of thermodynamic principle shows that albitization of plagioclase is not controlled by temperature and pressure in diagenesis, and that albitization of potash feldspar depends on the increase of temperature and pressure during a diagenetic process. Therefore, the albitization of plagioclase is shown in the early stage of diagenesis and albitization of potash feldspar appears only in the late stage of diagenesis.
出处
《地质论评》
CAS
CSCD
北大核心
2003年第2期155-161,T004,共8页
Geological Review
