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在密歇根半岛北部前寒武纪Portage湖熔岩系的杏仁伏、角砾状熔岩流项部含有自然铜,矿化带的年代与地壳掀斜作用的关系尚未清楚.关于矿化作用发生的问题,成矿溶液在掀斜作用前通过张开断裂上升的,还是已掀斜的玄武岩使成矿溶液通过渗透性高的带向上运移的呢?我们可以利用古地磁岩石磁性和岩石学来研究这个问题.磁铁矿的破裂和赤铁矿的形成可能是在矿化时期发生的.我们的研究认为,赤铁矿化也是矿化作用发生在任何明显掀斜之前,而且矿化作用持续的时间相当短,不能记录下地极的游移,可是这段时间仍是以求出长期变化中一段时间的平均数.
The relationship between the age of the mineralization belt and the crustal tilt is not clear in the alluvial volcanic and brecciated lava flows of the Early Cambrian Portage lava in the northern part of the Peninsula.As for the mineralization, Were the mineralization solution to migrate through the highly permeable zone by opening fractured, or tilted, basalts before tilting? We can use paleomagnetism, rock magnetism and petrology to study this Problem. The rupture of magnetite and the formation of hematite may occur during the mineralization, and our study suggests that hematite is also mineralization occurring before any obvious tilting, and the duration of mineralization Quite short, can not record the pole’s wandering, but this time is still in order to find the long-term changes in the average period of time.