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怀俄明东南马德雷山脉早元古界绿山组由双峰镁铁质和长英质火山岩组成。主要由角砾岩、块集岩、熔岩流和火山碎屑岩组成的岩层代表陆上和海底喷发作用的产物,部分是在河成环境和近滨海相环境中再沉积的。火山岩明显地显示出钙碱性特征,并且有与大陆边缘弧或演化洋弧系共有的许多地球化学特征。玄武岩低的镁数和镍含量要求30—40％橄榄石分离结晶,还有大多数不相容元素的高含量,高的(La/Sm)_N比值,以及低Zr/Nb之比需要一个不亏损或富集的地幔源。地球化学资料与长英质火山岩及共生的扎营河(Encampment River)花岗岩的成因相一致,上述火山岩与花岗岩是在相似于现代弧系的构造位置中由钙碱性玄武岩浅部分离结晶作用而形成。安山岩的近乎缺失可能反映分离结晶过程中地壳岩浆房安山质岩浆的滞留。
The Early Proterozoic Green Mountain Formation in the Sierra Madre Mountains, Wyoming, consists of bimodal mafic and felsic volcanic rocks. Rock formations, mainly composed of breccias, block rocks, lava flows and volcaniclastic rocks, represent the products of both onshore and submarine eruptions and are partly redeposited in both riverine and coastal environments. Volcanic rocks clearly show calc-alkaline features and have many geochemical features that are common to continental margin arcs or evolutionary ocean arcs. The low magnesium and nickel content of basalts require 30-40% olivine to separate and crystallize, as well as the high content, high (La / Sm) _N ratio of most incompatible elements, and the low Zr / Nb ratio Loss or enrichment of mantle sources. The geochemical data are consistent with the genesis of the Ordovician volcanics and the symbiotic Encampment River granites that were formed by crystallization from shallow parts of calc-alkaline basalts in structurally similar locations to modern arc systems . The near absence of andesite may reflect the detachment of the crustal magmatic anarcorphic magma during the separation and crystallization.