在北川断裂带与青川断裂带至金汤弧形构造前弧东翼外缘一带之间,为后龙门山;在北川断裂带与四川盆地西北边之间,为前龙门山。以往按传统习惯称后龙门山为“地槽”。笔者认为,以细碧角斑岩为代表的前震旦系,应是优地槽的特征。寒武系为海相碎屑岩夹泥质岩和酸至中性火山岩系,厚度大于1000米,未见化石,可能属优地槽性质。茂县群为 Between Beichuan fault belt and Qingchuan fault zone to the golden arc before the outer edge of the eastern front of the arc, between the Beilong fault zone and the northwestern edge of Sichuan Basin, the former Longmen Mountain. In the past, according to traditional habits after the Longmen Mountain as “trough.” In my opinion, the Pre-Sinian, represented by the Penpikan porphyry, should be characterized by its excellent characteristics. Cambrian marine clastic rocks with muddy rocks and acid to neutral volcanic rocks, the thickness of more than 1,000 meters, no fossils, may be an excellent trough properties. Maoxian group