Contrasting tectonic settings in Northern Chon Aike Igneous Province of Patagonia: subduction and mantle plume-related volcanism in the Marifil formation

The northern zone of the Chon Aike Igneous Province, located in the North Patagonian Massif, exhibits extensive outcrops of Jurassic volcanic rocks of the Marifil Formation. In the Arroyo Verde area, the initial volcanic stage of the Marifil Formation, that we denominate V0 (192.6 ± 2.5 Ma), includes coulées, megabreccias and lapilli tuffs assigned to plinian-type volcanism. This magmatism was generated by cold-wet-oxidized magmas that resemble those produced in active continental margins and volcanic arcs. The second stage, located unconformably over the first, includes welded lava-like ignimbrites, massive lapilli tuff and rhyolitic lava flow that resemble the Snake River-type volcanism. The magma that produces this volcanic stage exhibit the characteristics of hot-dry-reduced magmas emplaced in intraplate continental environments associated with continental rifting. This stage coincides with the V1 volcanic episode early recorded in the Marifil Formation.

位于北巴塔哥尼亚地块（North Patagonian Massif）的乔艾克火成岩省（Chon Aike Igneous Province）北部区域，广泛出露侏罗纪时期的马里菲尔组（Marifil Formation）火山岩。在阿罗约韦尔德（Arroyo Verde）地区，我们将马里菲尔组的初始火山阶段命名为V0（192.6 ± 2.5 Ma），该阶段包含归属于普林尼式（plinian-type）火山作用的熔岩流（coulées）、巨角砾岩（megabreccias）与火山砾凝灰岩（lapilli tuffs）。该套岩浆作用由冷湿氧化型岩浆形成，其特征与活动大陆边缘及火山弧环境下产出的岩浆相似。不整合覆于初始阶段之上的第二火山阶段，则包含熔结熔岩状熔结凝灰岩（welded lava-like ignimbrites）、块状火山砾凝灰岩与流纹岩熔岩流（rhyolitic lava flow），其火山作用特征类似斯内克河型（Snake River-type）火山作用。该阶段的岩浆，具备在与大陆裂谷（continental rifting）作用相关的板内大陆环境中侵位的热干还原型岩浆的特征。该火山阶段与此前在马里菲尔组中记录到的V1火山事件相吻合。