Upper Precambrian to lower Paleozoic crystalline basement of the Southern Pampean Ranges is composed of (1) a narrow western zone, having low to medium grade metamorphic rocks and relatively few granites and migmatites and (2) a wide central eastern Hercynotype low‐pressure zone with abundant granitoids. The internal structures fall into three distinct domains characterized by the following orientations: Dl, nearly E‐W; D2, NNW‐SSE; and D3, NNE‐SSW.The tectonic evolution is interpreted as having begun in an upper Precambrian orogenic cycle commencing with lithospheric rifting, followed by compression forming D1 structures. Next was a mobile belt cycle composed of two main stages. The first one, which generated the main tectonic features (D2) of the igneous—metamorphic complex, coincided with a syntectonic to late tectonic granitic intrusive event, with the principal metamorphic episode, and with Paleozoic Andean tectonic trends related to the activity of the Gondwanaland Pacific margin. The last one, was a fracturing and an open weak folding (D3) event with local low‐grade metamorphism; it occurred during t
展开▼
