On the basis of rock type, type of intrusion, chemistry, and age of rocks, two main groups of younger Early Paleoproterozoic igneous intrusive (plutonic) rocks have been distinguished within the Vishnu Basement Rocks. One group, which dates between 1.74 and 1.71 billion years ago, consists of large plutons such as the Zoroaster pluton, the Ruby pluton, and the Diamond Creek pluton. There is no noticeable baking and metamorphism of the country rock adjacent to them. Because of this, they were likely shallowly emplaced beneath the volcanic arc in which the metavolcanics and metasediments of the Granite Gorge Metamorphic Suite accumulated. In addition, these intrusive rocks have undergone all the deformation that has also affected their adjacent country rock. This further indicates that they are just slightly younger than the metavolcanic and metasedimentary rocks they intrude. This and their calc-alkaline granitic composition, which is similar to plutons forming in modern 'subduction zone related' volcanic arcs, indicates that they are remnants of early volcanic arc systems associated with Early Paleoproterozoic subduction zones. Comparable volcanic arc systems, which are associated with subduction zones, are active today in the Aleutian Islands and Indonesia (e.g., Sumatra and Java).