The southern portion of the Mesa Central (MC) physiographic province is covered by numerous Oligocene to Miocene volcanic successions that are part of the Sierra Madre Occidental silicic large igneous province. The MC merges with the Sierra Madre Occidental and the southern Basin and Range extensional province. The voluminous Villa Garcia-Loreto Volcanic Complex (VGLVC) is located in the southern portion of the MC and consists of predominantly rhyolitic lava flows, and voluminous products of explosive rhyolitic volcanism, mainly as lava-like to rheomorphic ignimbrite sheets. The volcanism in the area appears in two events, first, at 60.4 ± 0.3 Ma (K–Ar whole-rock age) with the fissure-fed eruption of an andesitic lava and second, with the fissure-fed eruption of two densely-welded, crystal-poor ignimbrites at 31.59 ± 0.14 Ma and 28.66 ± 0.07 Ma (⁴⁰Ar–³⁹Ar sanidine ages). Chondrite-normalized rare earth element patterns and primitive mantle normalized multi-element patterns show enrichment in light rare earth elements (LREE) and high field strength elements (HFSE). Geochemical analysis and mineral chemistry show that the andesitic magmas were generated by partial melting of the uppermost mantle in a subduction-related setting and ascended directly through the brittle crust and erupted along N-S trending faults. Rhyolitic magmas were generated by partial melting of the lower crust in an intra-plate and extensional setting, associated with an intense phase of the southern Basin and Range extension. During the ascent and storage in a shallow magma chamber fractional crystallization of mainly feldspars and pyroxene was the major process taking place in the evolution of the magma. Geophysical results suggest that the volcanic rocks of the VGLVC were originated by fissure-fed eruptions associated with the Loreto Graben fault. The major Basin and Range faults locally reach a depth of 7 km and trending in NNW-SSE direction. The combined results show that the Basin and Range extension favored the formation, ascent, and eruption of rhyolitic and andesitic magmas in the southern MC.

梅萨中部（MC）地理省的南部被许多渐新世至中新世火山岩层所覆盖，这是西马德雷西部硅质大火成岩省的一部分。MC与西马德雷山脉，南部盆地和山脉延伸省合并。巨大的Villa Garcia-Loreto火山复合体（VGLVC）位于MC的南部，主要由流纹岩性熔岩流和爆炸性流纹岩性火山岩的大量产物组成，主要是类熔岩到流变型火成岩片。该地区的火山活动有两次发生，首先是安第斯山熔岩的裂隙性火山喷发，发生在60.4±0.3 Ma（K-Ar全岩时代），其次是两次致密焊接的裂隙性火山喷发。 ，晶体贫乏的火成岩在31.59±0.14 Ma和28.66±0.07 Ma（⁴⁰ Ar– ³⁹Ar Sanidine年龄）。球粒晶归一化的稀土元素模式和原始地幔归一化的多元素模式显示出富含轻稀土元素（LREE）和高场强元素（HFSE）。地球化学分析和矿物化学表明，安山岩岩浆是由俯冲相关环境中最上层地幔的部分熔融而产生的，并直接通过脆性地壳上升，并沿NS趋势断裂喷发。流变岩浆是由于板内和伸展背景下地壳的部分融化而产生的，与南部盆地的强烈期相和范围伸展有关。在浅岩浆室内上升和储存期间，主要长石和辉石的部分结晶是岩浆演化的主要过程。地球物理结果表明，VGLVC的火山岩是由与Loreto Graben断层有关的裂隙性火山喷发形成的。盆地和山脉的主要断层局部深度达7 km，并在NNW-SSE方向上呈趋势。综合结果表明，盆地和山脉的延伸有利于南部MC流纹岩和安山岩岩浆的形成，上升和喷发。