Abstract This work reports on the geology and U–Pb LA-ICPMS zircon geochronology of a crustal section that is part of the Jurassic magmatic arc in the Magdalena quadrangle of north-central Sonora, Mexico. This rock succession is variably metamorphosed and strained as it was affected by Late Cretaceous shortening, intruded by early Tertiary granitoids, and further exhumed in the lower plate of the early Miocene Magdalena metamorphic core complex. The older and more extensively exposed Jurassic unit is the >3.5 km thick Sierra Guacomea rhyolite that is composed of massive to poorly bedded rhyolite, bedded quartz-phyric rhyolitic ignimbrite and interbedded ash-fall tuffs and quartz-rich sandstone beds. Three rhyolite samples collected at different localities of its outcrops yielded concordia ages of 175.2 ± 0.9, 171.7 ± 0.6, and 171.4 ± 0.7 Ma. The quartz-phyric Rancho La Vibora, Los Vallecitos, and the Agua Caliente rhyolitic domes that are associated with the Sierra Guacomea rhyolite yield concordia ages of 176 ± 0.8, 174.4 ± 0.9 and 173.1 ± 0.8 Ma, respectively. The Rancho Los Pozos unit composed of interbedded rhyolitic ash-fall tuff and flows, sandstone, siltstone and subordinate limestone beds has an estimated thickness of 600 m and yielded a crystallization concordia age of 170.7 ± 0.6 Ma from a rhyolite bed. The porphyritic El Rincon granite that intrudes into the Sierra Guacomea rhyolite yields crystallization ages of 167.43 ± 0.42 and 164.4 ± 0.7 in samples from different localities. The La Jojoba metasandstone that consists of foliated, quartz-rich to arkosic clastic strata of fluvial origin is at least 900 m thick; detrital zircons dated from three sandstone samples yielded dominantly Jurassic zircon grains with peak ages at 172, 170, and 163.7 Ma, and a combined maximum depositional age of ca. 163 Ma. The younger plutons are the porphyritic El Nopalito granite that has an interpreted crystallization age of 160.8 ± 0.6 Ma, and the leucocratic, two-mica, garnet-bearing La Cebolla granite that yielded a concordia age of 158.1 ± 1 Ma. These granitic intrusions record the waning magmatic pulses of the arc, in the study quadrangle, but their volcanic equivalents were not identified. Inherited zircon grains in the volcanic and plutonic units are only of Jurassic age, except by two Proterozoic zircon grains yielded by the El Nopalito granite. The El Salto granite augen gneiss is a xenolith dated at 1071.9 ± 5 Ma that indicates the presence of Grenvillian basement in the study area. Major- and trace-element geochemical data indicate that the volcanic and plutonic units are silica-rich, mostly high K calc-alkaline to shoshonitic rocks associated with a continental margin arc setting. The plutons are mostly peraluminous, and in conjunction with trace element geochemistry data, they suggest crustal assimilation of magmas emplaced in a probably thickened continental crust. Chondrite-normalized REE patterns and primitive mantle-normalized trace element diagrams also suggest partial melting and fractional crystallization processes. The ages obtained indicate that the arc in the study area developed from ca. 176 to 158 Ma, encompassing a 17 m.y. interval of magmatism and associated sedimentation. Regional correlation and geochronologic published data indicate that the arc crustal section of the Magdalena quadrangle is part of the Jurassic magmatic arc that regionally lasted from ca. 190 to 158 Ma.

中文翻译：

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墨西哥索诺拉州中北部马格达莱纳四边形侏罗纪岩浆弧的地质和年代学

摘要 这项工作报告了墨西哥索诺拉州中北部马格达莱纳四边形侏罗纪岩浆弧一部分的地壳剖面的地质和 U-Pb LA-ICPMS 锆石年代学。由于受到晚白垩世缩短的影响，受到早第三纪花岗岩的侵入，并在早中新世马格达莱纳变质核复合体的下板块进一步挖掘，该岩石序列发生了不同程度的变质和应变。更古老和更广泛暴露的侏罗纪单元是 > 3.5 公里厚的 Sierra Guacomea 流纹岩，它由块状至层状较差的流纹岩、层状石英-岩质流纹质凝灰岩和夹层灰烬凝灰岩和富含石英的砂岩层组成。在其露头的不同地点收集的三个流纹岩样品产生的协和年龄分别为 175.2 ± 0.9、171.7 ± 0.6 和 171.4 ± 0.7 Ma。与 Sierra Guacomea 流纹岩相关的石英岩 Rancho La Vibora、Los Vallecitos 和 Agua Caliente 流纹岩穹顶的协和年龄分别为 176 ± 0.8、174.4 ± 0.9 和 173.1 ± 0.8 Ma。Rancho Los Pozos 单元由流纹质灰凝灰岩和流、砂岩、粉砂岩和附属石灰岩层的互层组成，估计厚度为 600 m，从流纹岩层产生的结晶协和年龄为 170.7 ± 0.6 Ma。侵入到 Sierra Guacomea 流纹岩中的斑状 El Rincon 花岗岩在来自不同地点的样品中产生了 167.43 ± 0.42 和 164.4 ± 0.7 的结晶年龄。La Jojoba 变砂岩由叶状的、富含石英的至河流成因的长石质碎屑岩层组成，厚度至少为 900 m；从三个砂岩样品中测得的碎屑锆石主要是侏罗纪锆石颗粒，峰值年龄分别为 172、170 和 163.7 Ma，最大沉积年龄组合约为 163 马。较年轻的岩体是斑状的 El Nopalito 花岗岩，其解释的结晶年龄为 160.8 ± 0.6 Ma，以及白晶质、两云母、含石榴石的 La Cebolla 花岗岩，其协和年龄为 158.1 ± 1 Ma。这些花岗岩侵入体在研究四边形中记录了弧的减弱的岩浆脉冲，但没有确定它们的火山等效物。火山和深成岩单元中的继承锆石颗粒只有侏罗纪时代，除了 El Nopalito 花岗岩产生的两个元古代锆石颗粒。El Salto 花岗岩片麻岩是一种可追溯到 1071 年的包体。9 ± 5 Ma，表明研究区存在 Grenvillian 地下室。主要元素和微量元素地球化学数据表明，火山和深成岩单元富含二氧化硅，主要是高钾钙碱性到与大陆边缘弧环境相关的钾长石。岩体大多是过铝质的，结合微量元素地球化学数据，它们表明岩浆在可能增厚的大陆地壳中被地壳同化。球粒陨石归一化 REE 模式和原始地幔归一化微量元素图也表明部分熔融和分步结晶过程。获得的年龄表明研究区的弧是从约。176 至 158 Ma，包括 17 my 岩浆作用和相关沉积的间隔。区域相关性和已发表的地质年代学数据表明，马格达莱纳四边形的弧形地壳剖面是侏罗纪岩浆弧的一部分，从大约 190 到 158 毫安。