Zircon trace element geochemistry and Ti-in-zircon thermometry of the Linté Pan-African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications,Geological Journal

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Zircon trace element geochemistry and Ti-in-zircon thermometry of the Linté Pan-African granitoids, Central Cameroon: Constraints on the genesis of host magma and tectonic implications
Geological Journal ( IF 1.4 ) Pub Date : 2021-07-15 , DOI: 10.1002/gj.4208
Patrick Ayonta Kenne ₁ , Evine Laure Tanko Njiosseu ₁ , Sylvestre Ganno ₂ , Timoleon Ngnotue ₁ , Donald Hermann Fossi ₂ , Alexis Hamdja Ngoniri ₁ , Philomene Nga Essomba ₂ , Jean Paul Nzenti ₂

Affiliation

The Linté area belongs to the central part of the Adamawa-Yadé Domain (AYD) within the Pan-African Central African Fold Belt (CAFB) in Cameroon. This area is dominated by Neoproterozoic high-K calc-alkaline syenite and monzonite intruding Archean to Palaeoproterozoic gneisses. In this contribution, trace element compositions of zircon obtained using laser ablation inductively coupled plasma mass spectrometry are used to constrain the petrogenesis and tectonic setting of Linté area. The analysed zircon grains display restricted ranges of Hf contents with an average of 8,197 ppm in syenite, 8,220 ppm in alkali-feldspar syenite, and 9,026 ppm in monzonite. They display high Th/U ratios (>0.5) typical of magmatic zircons. The monzonite zircons have a higher ∑REE content (483.42 ppm) than the syenite zircons (237.70 ppm). The chondrite-normalized rare-earth element (REE) diagram of Linté samples shows very similar patterns, characterized by a steeply rising slope due to important heavy rare-earth element enrichment relative to light rare-earth element, with distinctive positive Ce and negative Eu anomalies. The application of the Ti-in-zircon thermometer reveals a wide range of crystallization temperatures (574–1,137°C for syenites and 713–1,008°C for monzonite), implying a deep level of melting, likely within the lower continental crust of the CAFB. The integration of geochemical behaviours of some trace elements (U, Hf, Zr, Ce, Th, and Nb), together with discrimination diagrams, suggests the crystallization of a continental crust-derived magma under variable oxidation states and emplacement in a magmatic-arc setting. This finding represents and adds on to the N-S geodynamic convergence model between the AYD and the northern border of the Congo Craton.

中文翻译：

喀麦隆中部 Linté Pan-African 花岗岩的锆石微量元素地球化学和 Ti-in-zircon 温度测量：对寄主岩浆成因和构造意义的限制

林特地区属于喀麦隆泛非中非褶皱带 (CAFB) 内阿达马瓦-亚德域 (AYD) 的中部。该区以新元古代高钾钙碱性正长岩和侵入太古代至古元古代片麻岩的二长岩为主。在这项贡献中，使用激光烧蚀电感耦合等离子体质谱法获得的锆石的微量元素组成用于限制林特地区的岩石成因和构造环境。分析的锆石晶粒显示 Hf 含量s 的限制范围正长岩平均为 8,197 ppm，碱长石正长石为 8,220 ppm，二长石为 9,026 ppm。它们显示出岩浆锆石典型的高 Th/U 比 (>0.5)。二长岩锆石的∑REE 含量（483.42 ppm）高于正长岩锆石（237.70 ppm）。Linté 样品的球粒陨石归一化稀土元素 (REE) 图显示出非常相似的模式，其特征是由于相对于轻稀土元素重要的重稀土元素富集，斜率急剧上升，具有明显的正 Ce 和负 Eu异常。Ti-in-zircon 温度计的应用揭示了广泛的结晶温度（正长岩为 574-1,137°C，二长岩为 713-1,008°C），这意味着深度熔化，可能在下大陆地壳内咖啡厅。一些微量元素（U、Hf、Zr、Ce、Th 和 Nb）的地球化学行为的综合，连同判别图，表明大陆地壳来源的岩浆在不同氧化态下结晶并在岩浆弧中侵位环境。这一发现代表并补充了 AYD 和刚果克拉通北部边界之间的 NS 地球动力学收敛模型。

更新日期：2021-09-02

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