This article presents textures, mineral chemistry, and geothermobarometric data for the southeastern Pinheiro Machado Complex rocks (PMC), eastern domain of the Dom Feliciano Belt, Rio Grande do Sul, Brazil. The PMC is composed by comagmatic intrusions of quartz diorite, tonalite, and granodiorite with medium‐ to fine‐grained equigranular and medium‐grained inequigranular textures with subordinate alkali‐feldspar macrocrystals. Partial melting features are observed in the comagmatic as melt pools and melt films. Amphibolite xenoliths also occur, presenting sharp‐angled to rounded contacts with the intrusions and evidences of partial assimilation, marked by mafic schlierens. Electron probe microanalyzer punctual analyses were used to classify amphibole, plagioclase, biotite, epidote, and titanite, as well as for the calculations of the crystallization P–T conditions. Amphiboles consist of pargasite for the comagmatic intrusions, and Mg‐hornblende for the amphibolite. Plagioclase ranges from oligoclase to andesine (An_15‐40) in both units. Biotite corresponds to annite, with Fe/(Fe + Mg) > 0.3. The epidote has mostly magmatic characteristics in the comagmatic intrusions, with pistacite content 25–30%. Titanite has two distinct textures, titanite I is well formed, subhedral to euhedral, with up to 3 mm; while titanite II is anhedral with size >1 mm and rounded shapes, being both chemically homogeneous. The estimated P–T conditions for the amphibolite crystallization, using plagioclase‐hornblende geothermometer are 650–850°C and 3.62–4.95 kbar, whereas the conditions from the comagmatic intrusions are 714–871°C and 4.44–6.10 kbar. In the mineral phases there is a prevalence in the recrystallization field between subgrain rotation (SGR) and grain boundary migration (GBM) in submagmatic flow. These new data indicate that possibly at the end of PMC crystallization, late magmatic fluids caused re‐equilibrium of mineral phases, mainly in biotite and feldspars. Finally, we suggest that the PMC is the result of continuous and repeated comagmatic intrusions in a continental magmatic arc setting at a depth of 20–30 km in an amphibolitic continental crust.

中文翻译：

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有助于理解Pinheiro Machado复合体（巴西Dom Feliciano带）：质地，矿物化学和结晶条件的研究

本文介绍了巴西南里奥格兰德州Dom Feliciano带东区东南部的Pinheiro Machado复杂岩石（PMC）东南的纹理，矿物化学和地热气压数据。PMC由石英闪长岩，方钠石和花岗闪长岩的岩浆侵入组成，具有中等至细粒度的等粒和中等粒度的不等粒组织，并带有次要的碱长石大晶体。在共岩中观察到部分熔融特征，如熔池和熔膜。也出现角闪石异岩，与侵入体呈锐角到圆形接触，并表现出部分吸收的迹象，以铁镁石线虫为特征。电子探针显微分析仪的点检分析可用于区分闪石，斜长石，黑云母，埃迪奥德和钛铁矿，以及结晶PT条件的计算。闪石由辉石组成，用于岩浆岩侵入，镁角闪石用于闪石。斜长石酶的范围从寡糖酶到安地辛（An_15-40）。黑云母对应于铁矿，Fe /（Fe + Mg）> 0.3。岩浆岩在岩浆岩侵入体中主要具有岩浆岩的特征，火山石含量为25％至30％。钛矿具有两种不同的织构，钛矿I形成良好，从正反面到正反面，最大3毫米。而钛矿II是直径大于1毫米且呈圆形的正反面，在化学上均具有均一性。使用斜长石-角闪闪地热仪估计的角闪石结晶的PT条件是650–850°C和3.62–4.95 kbar，而岩浆侵入的条件是714–871°C和4.44–6.10 kbar。在矿物相中，在亚岩浆流中，亚晶粒旋转（SGR）和晶界迁移（GBM）之间的再结晶场普遍存在。这些新数据表明，可能在PMC结晶结束时，晚期岩浆流体引起矿物相的重新平衡，主要在黑云母和长石中。最后，我们认为PMC是在两性大陆结壳中深度20-30 km的大陆岩浆弧环境中连续不断重复的岩浆侵入的结果。