Provenance, age constraints and metamorphism of Ediacaran metasedimentary rocks from the El Triunfo Complex (SE Chiapas, México): evidence for Rodinia breakup and Iapetus active margin

Metasedimentary rocks from the El Triunfo Complex (Jocote Unit) in the southern Chiapas Massif (SE México) are constituted mainly by sillimanite-rich micaschist, locally intercalated with marble and calc-silicate rocks. Mafic rocks (now amphibolite) intruded the sequence prior to deformation and folding. Peak metamorphic conditions are estimated by geothermobaromerty at ~6.0 kbar and ~650ºC. The timing of the metamorphic event is dated by LA-MC-ICPMS analysis on zircon rims at 438+23/–12 Ma. Furthermore, detrital zircon grains yield mainly Stenian–Tonian and minor early Mesoproterozoic ages, indicating provenance from Grenville-type orogens (such as Oaxaquia) and some older cratonic sources. The 87Sr/86Sr values of 0.70775–0.70777 and the δ13C values from +1.9‰ to +2.7‰ in associated calcite marble define the time of deposition between 600 and 580 Ma. Geochemical markers from metapelite samples (such as La/Th > 3.94, La/Sc > 3.72, Th/U > 8.19, Th/Co > 0.42 and CIA = 74 to 83), as well as Sm–Nd isotope data (εNdi = −8.1 to −4.0, TDM(Nd) = 1.65–1.32 Ga) suggest weathering of Mesoproterozoic felsic rocks during temperate to warm climate. Furthermore, Zr/Sc values (9.1–21.0), chondrite-normalized REE patterns [La/Yb]N = 10.3–23.3, Eu/Eu*

墨西哥东南部恰帕斯地块南部的埃尔特里温福杂岩（霍科特岩组）中的变沉积岩，主要由富红柱石云母片岩构成，局部夹有大理岩与钙硅酸盐岩。镁铁质岩（现已变质为角闪岩）在变形与褶皱作用发生前侵入该地层序列。通过地热温压计（geothermobarometry）估算得到其峰期变质条件约为6.0 kbar与650℃。变质事件的时代通过LA-MC-ICPMS对锆石边部的分析限定为438+23/–12 Ma。碎屑锆石颗粒的年龄主要集中在斯泰尼纪-通古斯纪，少量为早中元古代，指示物源来自格林威尔型造山带（如Oaxaquia瓦哈卡地块）以及部分更古老的克拉通物源。伴生方解石大理岩的87Sr/86Sr比值介于0.70775~0.70777之间，δ13C值为+1.9‰~+2.7‰，据此限定其沉积时代为600~580 Ma。变泥质岩样品的地球化学指标（如La/Th>3.94、La/Sc>3.72、Th/U>8.19、Th/Co>0.42，以及化学风化指数CIA为74~83），以及钐-钕同位素数据（初始εNd值εNdi为-8.1~-4.0，Nd模式年龄TDM(Nd)为1.65~1.32 Ga）表明，中元古代长英质岩在温和至温暖的气候条件下发生风化作用。此外，Zr/Sc比值（9.1~21.0）、球粒陨石标准化稀土元素配分模式[La/Yb]N=10.3~23.3、Eu/Eu*