Quantitative petrographic, structural, and textural parameters are integrated with geological, geochemical, and Sr-isotope data to examine the emplacement, growth processes, and magmatic evolution of the high-Ti tholeiitic Limeira Intrusion, in the Paraná Magmatic Province of SE Brazil. Our data strongly support a multiple-stage evolution, owing to the nested emplacement of distinct crystal-bearing magma pulses that probably evolved independently, except at their boundaries. A stage of cooling and crystallization between magma injections results in a stepwise T–t path, leading to variations in the plagioclase residence times and effective growth rates inwards, also occasioning sudden changes in crystal shape and size at the boundaries of each magma pulse. The time delay between pulses allows preservation of internal ‘chilled margins’ and the development of near-rigid surfaces at their contacts, increasing the alignment and clustering of crystals during magma replenishment. Isotopic and textural data demonstrate a complex assembly history, in which the appearance of mixed plagioclase populations between magma pulses coincides with the onset of initial Sr isotope ratio increase, which can be attributed to a locally enhanced cooling rate, and the extraction of residual melts from the previous crystallizing batches and mixing with the younger pulses. Typical C- and S-shaped MgO (wt%) compositional profiles within individual pulses indicate that the first one probably evolved by in situ fractional crystallization followed by melt migration inward, whereas the younger ones have contributions from both compaction of the lowermost crystallization front and compositional convection. Mafic globular structures are found at the boundaries of magma pulses and constituting the mafic-rich layers in layered rocks. They are interpreted as evidence for chemical disequilibrium, arguably associated with the trigger of silicate liquid immiscibility. The upwards compositional convection of the silica-rich residual liquid and the accumulation of the Fe–Ti–P-rich crystalbearing end-member in the bottom of the latest magma pulses might represent the most significant mechanism of differentiation in the Limeira Intrusion.

中文翻译：

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巴西巴拉那岩浆省 Limeira 侵入体中多个片状岩浆脉冲的结构和地球化学证据

定量岩相学、结构和结构参数与地质、地球化学和 Sr 同位素数据相结合，以检查巴西东南部巴拉那岩浆省的高钛拉斑斑岩 Limeira 侵入体的侵位、生长过程和岩浆演化。我们的数据强烈支持多阶段演化，因为不同的含晶体岩浆脉冲的嵌套位置可能独立演化，除了它们的边界。岩浆注入之间的冷却和结晶阶段导致逐步的 T-t 路径，导致斜长石停留时间和向内有效生长速率的变化，也导致每个岩浆脉冲边界处晶体形状和尺寸的突然变化。脉冲之间的时间延迟允许保留内部“冷却边缘”并在其接触处形成近刚性表面，从而在岩浆补充过程中增加晶体的排列和聚集。同位素和结构数据显示了复杂的组装历史，其中岩浆脉冲之间混合斜长石群的出现与初始 Sr 同位素比增加的开始相吻合，这可归因于局部提高的冷却速率，以及从岩浆中提取残余熔体先前的结晶批次并与较年轻的脉冲混合。单个脉冲内典型的 C 形和 S 形 MgO（wt%）组成分布表明，第一个可能是通过原位分步结晶演化而来，然后是熔体向内迁移，而较年轻的有来自最低结晶前沿的压实和成分对流的贡献。镁铁质球状结构存在于岩浆脉冲的边界，构成层状岩石中富含镁铁质的层。它们被解释为化学不平衡的证据，可以说与硅酸盐液体不混溶的触发因素有关。最近一次岩浆脉冲底部富含二氧化硅的残余液体的向上成分对流和富含 Fe-Ti-P 晶体的端元的积累可能代表了 Limeira 侵入体中最重要的分异机制。镁铁质球状结构存在于岩浆脉冲的边界，构成层状岩石中富含镁铁质的层。它们被解释为化学不平衡的证据，可以说与硅酸盐液体不混溶的触发因素有关。最近一次岩浆脉冲底部富含二氧化硅的残余液体的向上成分对流和富含 Fe-Ti-P 晶体的端元的积累可能代表了 Limeira 侵入体中最重要的分异机制。镁铁质球状结构存在于岩浆脉冲的边界，构成层状岩石中富含镁铁质的层。它们被解释为化学不平衡的证据，可以说与硅酸盐液体不混溶的触发因素有关。最近一次岩浆脉冲底部富含二氧化硅的残余液体的向上成分对流和富含 Fe-Ti-P 晶体的端元的积累可能代表了 Limeira 侵入体中最重要的分异机制。