Abstract The Conlara Metamorphic Complex, the easternmost complex of the Sierra de San Luis, is a key unit to understand the relationship between the late Proterozoic-Early Cambrian Pampean and the Upper Cambrian-Middle Ordovician Famatinian orogenies of the Eastern Sierras Pampeanas. The Conlara Metamorphic Complex extends to the east to the foothills of the Sierra de Comechingones and to the west up the Rio Guzman shear zone. The main rock types of the CMC are metaclastic and metaigneous rocks that are intruded by Ordovician and Devonian granitoids. The metaclastic units comprise fine to medium-grained metagreywackes and scarce metapelites with lesser amounts of tourmaline schists and tourmalinites whereas the metaigneous rocks encompass basic and granitoids rocks. The former occur as rare amphibolite interlayered within the metasedimentary rocks. The granitic component corresponds to a series of orthogneisses and migmatites (stromatite and diatexite). The CMC is divided in four groups based on the dominant lithological associations: San Martin and La Cocha correspond mainly to schists and some gneisses and Santa Rosa and San Felipe encompass mainly paragneisses, migmatites and orthogneisses. The Conlara Metamoprphic Complex underwent a polyphase metamorphic evolution. The penetrative D2-S2 foliation was affected by upright, generally isoclinal, N-NE trending D3 folds that control the NNE outcrop patterns of the different groups. An earlier, relic S1 is preserved in microlithons. Discontinuous high-T shear zones within the schists and migmatites are related with D4 whereas some fine-grained discontinuous shear bands attest for a D5 deformation phase. Geochemistry of both non-migmatitic metaclastic units and amphibolites suggest that the Conlara Metamorphic Complex represents an arc related basin. Maximun depositional ages indicate a pre- 570 Ma deposition of the sediments. An ample interval between sedimentation and granite emplacement in the already metamorphic complex is indicated by the 497 ± 8 Ma age of El Penon granite. D1-D2 history took place at 564 ± 21 Ma as indicated by one PbSL age calculated for the M2 garnet of La Cocha Group. D3 is constrained by the pervasively solid-state deformed Early Ordovician granitoids which exhibits folded xenoliths of the D1-D2 deformed metaclastic rocks. Pressure-temperature pseudosections were calculated for one amphibolite using the geologically realistic system MnNCKFMASHTO (MnO–Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3). Peak metamophic conditions (M2) indicate 6 kbar and 620 °C. Late chlorite on the rims and in cracks of garnet, along with titanite rims on ilmenite and matrix plagioclase breaking down to albite suggests that the P-T path moved back down. Monazite analyses yield isochron Th–U–Pb ages ranging from 446 to 418 Ma. The oldest age of 446 ± 5 Ma correspond to a migmatite from the Santa Rosa Group. Monazites in samples from the La Cocha and the San Martin group crystallized at decreasing temperatures, followed by the 418 ± 10 Ma low-Y2O3 monazites in one sample of the la Cocha Group that was also obtained from a migmatite, and would likely mark a later stage of a retrograde metamorphism New CHIME monazite ages presented here likely represent post-peak fluid assisted recrystallization that are similar to amphibole and muscovite cooling ages. Therefore the monazite ages may represent a re-equilibration of the monazite on the cooling path of the basement complex.

中文翻译：

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Conlara 变质杂岩体：岩性、物源、变质岩的变质限制和独居石年代学

摘要 圣路易斯山脉最东端的康拉拉变质杂岩体是了解晚元古代—早寒武世潘佩世与上寒武世—中奥陶世法马提阶造山带关系的关键单元。Conlara 变质复合体向东延伸至 Sierra de Comechingones 山麓，向西延伸至 Rio Guzman 剪切带。CMC的主要岩石类型是奥陶系和泥盆系花岗岩侵入的变质岩和变火成岩。变质岩单元包括细粒至中粒变灰岩和稀有变泥质岩，电气石片岩和电气石数量较少，而变火成岩包括基性和花岗质岩石。前者以稀有的角闪岩夹在变质沉积岩中而出现。花岗质成分对应于一系列正方麻岩和混合岩（叠层石和透闪岩）。CMC 根据主要的岩性组合分为四组：San Martin 和 La Cocha 主要对应于片岩和一些片麻岩，Santa Rosa 和 San Felipe 主要包括副片麻岩、混合岩和正方麻岩。Conlara Metamoprphic Complex 经历了多相变质演化。穿透性 D2-S2 叶理受直立的、通常等斜的、N-NE 趋势的 D3 褶皱的影响，这些褶皱控制着不同组的 NNE 露头模式。早期的遗物 S1 保存在微石中。片岩和混合岩内的不连续高 T 剪切带与 D4 相关，而一些细粒不连续剪切带证明 D5 变形阶段。非混杂变质碎屑单元和角闪岩的地球化学表明，康拉拉变质杂岩体代表了一个弧形相关盆地。最大沉积年龄表明沉积物在 570 Ma 之前沉积。El Penon 花岗岩的年龄为 497 ± 8 Ma，表明在已经变质的复合体中沉积和花岗岩侵位之间有足够的间隔。D1-D2 历史发生在 564 ± 21 Ma，如为 La Cocha Group 的 M2 石榴石计算的一个 PbSL 年龄所示。D3 受到普遍固态变形的早奥陶世花岗岩的限制，该花岗岩显示出 D1-D2 变形变质岩的折叠捕虏体。使用地质现实系统 MnNCKFMASHTO（MnO-Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3）计算了一种角闪岩的压力-温度假截面。峰值变质条件 (M2) 表示 6 kbar 和 620 °C。边缘和石榴石裂缝中的晚期绿泥石，以及钛铁矿上的钛铁矿边缘和分解为钠长石的基质斜长石，表明 PT 路径向下移动。独居石分析得出等时线 Th-U-Pb 年龄范围为 446 至 418 Ma。最古老的 446 ± 5 Ma 年龄对应于来自 Santa Rosa 群的混合岩。来自 La Cocha 和 San Martin 组的样品中的独居石在降低的温度下结晶，随后是 418 ± 10 Ma 低 Y2O3 的独居石，在同样从混合岩中获得的 la Cocha 组的一个样品中，并且可能标志着逆行变质作用的后期阶段 此处呈现的新 CHIME 独居石年龄可能代表峰后流体辅助再结晶，类似于角闪石和白云母冷却年龄。因此，独居石年龄可能代表独居石在基底复合体的冷却路径上的重新平衡。