Neoproterozoic pre-collisional events recorded in the Sergipano belt, Southern Borborema Province, West Gondwana

The Canindé Domain is crucial for understanding the pre-collisional events in Sergipano Belt, Borborema Province, especially during the Late Stenian/Early Tonian (740–680 Ma). We present thermobarometric, geochronology, and isotopic studies of the metavolcanosedimentary rocks of the Novo Gosto unit. The calculated metamorphic conditions resulted in a range of T: 600–740°C and P: 3.5–10.0 kbar for non-mylonitic amphibolites and values of T: 636–808°C and P: 7.0–12.0 kbar for mylonites, both of amphibolite facies. The minimum metamorphic conditions imprint in these rocks are T: 390°C and P: 2.5 kbar, indicating retrometamorphism in greenschist facies. The probable age of the peak metamorphic event was obtained in zircon rims from a quartzite at 692 ± 8.5 Ma. U-Pb detrital zircon and Nd model ages of the metasedimentary rocks point out Early Tonian as primary source rocks. Subordinate contributions of Mesoproterozoic, Paleoproterozoic, and Neoarchean sources were also recognized. These primary sources are related to Cariris Velhos event rocks, whereas the subordinate sources are from the Pernambuco-Alagoas superterrane. Early Tonian and Late Stenian ages were recognized for the first time in the Canindé Domain, with U-Pb zircon ages of 1005 ± 3 and 989 ± 6 Ma in amphibolites and mylonitized granites, mostly outcropping at the southwestern limit of the area. New ages were also obtained in the Novo Gosto surrounding intrusions: Canindé Layered Gabbroic Intrusion (~718 Ma), Garrote (~715 Ma) and Curralinho/Boa Esperança (~708 Ma) metagranites, and Gentileza metavolcanic rock (~700), which integrate the early pre-collisional magmatism of the Sergipano Belt (~740-680 Ma). Finally, U-Pb zircon ages were obtained in the Poço Redondo Domain, potential source area of the Novo Gosto metasedimentary rocks, resulting in ages of 957 ± 11 and 988 ± 15 Ma. The new data bring perspective to future correlations with adjacent belts and the understanding of the structuration of West Gondwana during the Brasiliano-Pan-African Orogeny.

卡尼德地体（Canindé Domain）对于厘清博尔博雷马省（Borborema Province）塞尔吉皮造山带（Sergipano Belt）的碰撞前构造事件至关重要，尤其针对斯泰内纪晚期（Late Stenian）/托南纪早期（Early Tonian，740–680 Ma）这一阶段。本研究针对诺沃戈斯托岩组（Novo Gosto Unit）的变火山沉积岩（metavolcanosedimentary rocks）开展了温压测定、地质年代学与同位素研究。计算得到的变质条件显示：非糜棱岩化角闪岩的温度区间为600–740°C，压力区间为3.5–10.0 kbar；糜棱岩化角闪岩的温度区间为636–808°C，压力区间为7.0–12.0 kbar，二者均属于角闪岩相（amphibolite facies）。上述岩石记录的最低变质条件为390°C、2.5 kbar，指示其经历了绿片岩相（greenschist facies）退变质作用。对一块石英岩的锆石边（zircon rims）进行定年，得到峰期变质事件的可能年龄为692 ± 8.5 Ma。变沉积岩的碎屑锆石（detrital zircon）U-Pb年龄与Nd模式年龄（Nd model ages）表明，其主要物源为托南纪早期岩石，同时识别出中元古代、古元古代及新太古代物源的次要贡献。上述主要物源与卡里里斯韦卢什事件（Cariris Velhos event）相关岩石对应，而次要物源则来自伯南布哥-阿拉戈斯地体（Pernambuco-Alagoas superterrane）。本研究首次在卡尼德地体中识别出斯泰内纪晚期与托南纪早期的年龄数据：角闪岩与糜棱岩化花岗岩的U-Pb锆石年龄分别为1005 ± 3 Ma与989 ± 6 Ma，二者主要出露于研究区西南边界。诺沃戈斯托岩组周边的侵入体也获得了新的定年结果：卡尼德层状辉长岩侵入体（Canindé Layered Gabbroic Intrusion，~718 Ma）、加罗特（Garrote，~715 Ma）变质花岗岩（metagranites）、库拉林霍/博阿埃斯佩兰萨（Curralinho/Boa Esperança，~708 Ma）变质花岗岩，以及Gentileza变火山岩（metavolcanic rock，~700 Ma），这些岩体均属于塞尔吉皮造山带（~740–680 Ma）的早期碰撞前岩浆作用（pre-collisional magmatism）序列。此外，本研究还对诺沃戈斯托变沉积岩的潜在物源区——波孔雷东多地体（Poço Redondo Domain）开展了锆石U-Pb定年，得到957 ± 11 Ma与988 ± 15 Ma的年龄数据。本研究的新数据为后续与相邻造山带的对比，以及对巴西利亚诺-泛非造山运动（Brasiliano-Pan-African Orogeny）期间西冈瓦纳（West Gondwana）构造演化的认识提供了全新视角。