Oligocene explosive volcanism is widespread in the central and eastern portion of the Mesa Central (MC), but the origin of the rhyolitic magmas is still under discussion. The Guanamé Ignimbrite is located in the northern portion of the Salinas-Villa de Ramos volcanic field (SVRVF) and a typical rhyolitic and porphyric Oligocene ignimbrite in the central and eastern portion of the MC. U–Pb zircon single grain age determination reveals a crystallization between 30.61 ± 0.73 Ma and 30.73 ± 0.39 Ma and an eruption at 30.12 ± 0.45 Ma (K–Ar whole rock). 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 features and mineral chemistry show that the rhyolitic magmas generated in an intra-plate and extensional setting from partial melting of the lower crust. During the ascent and storage in a shallow magma chamber, fractional crystallization of mainly plagioclase and oxides was the major process taking place in the evolution of the magma. Rhyolite-MELTS models reveal that these rhyolitic magmas were generated by partial melting of the well-studied lower crust in the MC. The models result in a similar mineral assemblage as observed in the samples. The mineral composition and crystallization temperatures of feldspars analyzed in this study are similar to the models confirming the lower crustal origin.

渐新世爆发性火山活动在 Mesa Central (MC) 的中部和东部普遍存在，但流纹质岩浆的成因仍在讨论中。Guanamé Ignimbrite 位于 Salinas-Villa de Ramos 火山区 (SVRVF) 的北部，是 MC 中部和东部的典型流纹质和斑状渐新世 ignimbrite。U-Pb 锆石单粒年龄测定揭示了 30.61 ± 0.73 Ma 和 30.73 ± 0.39 Ma 之间的结晶和 30.12 ± 0.45 Ma（K-Ar 全岩）的喷发。球粒陨石归一化稀土元素图案和原始地幔归一化多元素图案显示富含轻稀土元素 (LREE) 和高场强元素 (HFSE)。地球化学特征和矿物化学表明，流纹质岩浆形成于下地壳部分熔融的板内和伸展环境中。在浅层岩浆房上升和贮存过程中，以斜长石和氧化物为主的分异结晶是岩浆演化的主要过程。流纹岩-熔体模型显示，这些流纹质岩浆是由经过充分研究的 MC 下地壳的部分熔融产生的。这些模型产生了与样品中观察到的相似的矿物组合。本研究中分析的长石的矿物成分和结晶温度与确认下地壳成因的模型相似。主要是斜长石和氧化物的分步结晶是岩浆演化过程中发生的主要过程。流纹岩-熔体模型显示，这些流纹质岩浆是由经过充分研究的 MC 下地壳的部分熔融产生的。这些模型产生了与样品中观察到的相似的矿物组合。本研究中分析的长石的矿物成分和结晶温度与确认下地壳成因的模型相似。主要是斜长石和氧化物的分步结晶是岩浆演化过程中发生的主要过程。流纹岩-熔体模型显示，这些流纹质岩浆是由经过充分研究的 MC 下地壳的部分熔融产生的。这些模型产生了与样品中观察到的相似的矿物组合。本研究中分析的长石的矿物成分和结晶温度与确认下地壳成因的模型相似。