The southern section of the Paraná-Etendeka large igneous province exposes a sequence of heterogeneous Low-Ti lava packages that range compositionally from olivine tholeiites to rhyolites. The recent advances in the volcanic stratigraphy provide a high-resolution framework that constrains the spatial and temporal evolution of the lava sequence. The stratigraphy is formed by Low-Ti lavas, separated in four volcanic units, namely: Torres, Vale do Sol, Palmas and Esmeralda. Our data shows that individual volcanic units can be separated chemically and represent distinct batches of magma. The composition of erupted lavas is mostly controlled by a complex interplay between source composition and crystallization (±assimilation) within the crust. The magmatic plumbing system evolved gradually from the onset, towards the climax and waning phase of magmatism. LIP onset is composed by more primitive (MgO > 5%) pahoehoe basalt lava flows of the Torres Formation. These low-volume eruptions were fed by a poorly connected magmatic plumbing system focused within the lower crust. Geochemical evidence suggests that the parental basalts of Torres Formation were derived from picritic primary magmas that have evolved by fractional crystallization and assimilation of enriched lithospheric materials. The main phase of magmatism is formed by thick (>20 m), tabular, crystal-poor lavas with evolved composition, including the basaltic andesite of the Vale do Sol Formation and silicic rocks of the Palmas Formation. These large volume eruptions were formed by extensive fractional crystallization (+assimilation) of precursor basaltic magmas and directly fed by shallow magma chambers within the upper crust. The waning phase of magmatism, recorded in the Esmeralda Formation basalts-basaltic andesite, is marked by low-volume Hawaiian-like eruptions of compound lava flows at the surface and the retraction of the magmatic plumbing system at depth. These lavas also mark a shift towards more primitive (asthenospheric) compositions and the shallowing of mantle melting, reflecting the progressive extension of lithosphere during magmatism. For the Low-Ti lava sequence of the Paraná-Etendeka, the surface expression and composition of lava fields are directly controlled by crystallization (+assimilation) processes, and these petrological processes can account for broad geochemical variations within large igneous provinces.

中文翻译：

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巴拉那-埃滕德卡大火成岩省南部低钛熔岩的岩浆演化

巴拉那-埃滕德卡大型火成岩省的南部暴露出一系列异质低钛熔岩包，其成分范围从橄榄石拉斑岩到流纹岩。火山地层学的最新进展提供了一个高分辨率的框架，限制了熔岩序列的空间和时间演化。地层由低钛熔岩形成，分为四个火山单元，即：托雷斯、Vale do Sol、帕尔马斯和埃斯梅拉达。我们的数据表明，单个火山单元可以通过化学方法分离，并代表不同批次的岩浆。喷发熔岩的成分主要受源成分和地壳内结晶（±同化）之间复杂的相互作用控制。岩浆管道系统从岩浆作用的爆发、高潮和消退阶段逐渐演化。LIP 起始点由托雷斯组 (Torres Formation) 的更原始 (MgO > 5%) 帕霍霍玄武岩熔岩流组成。这些小量的喷发是由集中在下地壳内连接不良的岩浆管道系统供给的。地球化学证据表明，托雷斯组的母体玄武岩源自苦味质原生岩浆，这些岩浆是通过富集岩石圈物质的分步结晶和同化而演化而来的。岩浆作用的主要阶段是由厚（>20 m）、板状、贫晶熔岩形成，其成分已演化，包括 Vale do Sol 组的玄武质安山岩和 Palmas 组的硅质岩。这些大量喷发是由前体玄武岩浆的广泛分异结晶（+同化）形成的，并直接由上地壳内的浅岩浆室供给。埃斯梅拉达组玄武岩-玄武质安山岩中记录的岩浆活动减弱阶段的特点是地表复合熔岩流的低量夏威夷式喷发以及岩浆管道系统在深处的收缩。这些熔岩还标志着向更原始（软流圈）成分的转变和地幔融化的变浅，反映了岩浆作用期间岩石圈的逐渐扩展。对于Paraná-Etendeka 的低钛熔岩序列，熔岩场的表面表达和成分直接受结晶（+同化）过程控制，这些岩石学过程可以解释大型火成岩省内广泛的地球化学变化。