Therefore, the presence of abundant 4-methyl steranes is a necessary but not sufficient indicator for the Wenchang Formation source in the eastern Pearl River Mouth Basin.
因此，4-甲基甾烷的存在不能作为判识珠江口盆地东部油源主要是文昌组的唯一证据。
In the Eastern Sub basin the shallow and the deep magnetic sources have the same time and mechanism in formation, and are controlled by the seafloor spreading.
而东部次海盆深部和浅部磁异常的磁源具有同时性和相同形成机理，是通过海底扩张作用的方式形成的。
A lot of Yanshanian intermediate acid magmatic rocks in eastern China have similar geochemical characteristics to the adakite, their formation environment however is unrelated to subduction process.
中国东部燕山期有许多中酸性岩浆岩类似埃达克岩的地球化学特征，但其形成环境却与消减作用无关。
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