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Eoarchean to Neoproterozoic Detrital Zircons from the South of Meiganga Gold-Bearing Sediments (Adamawa, Cameroon): Their Closeness with Rocks of the Pan-African Cameroon Mobile Belt and Congo Craton
Minerals ( IF 2.2 ) Pub Date : 2021-01-15 , DOI: 10.3390/min11010077
Nguo Sylvestre Kanouo , Arnaud Patrice Kouske , Gabriel Ngueutchoua , Akella Satya Venkatesh , Prabodha Ranjan Sahoo , Emmanuel Archelaus Afanga Basua

The core of detrital zircons from the southern Meiganga gold-bearing placers were analyzed by Laser Ablation Split Stream analytical techniques to determine their trace element abundances and U-Pb ages. The obtained data were used to characterize each grain, determine its formation condition, and try to trace the provenance. The Hf (5980 to 12010 ppm), Y (27–1650 ppm), U (25–954 ppm), Th (8–674 ppm), Ti (2–256 ppm), Ta, Nb, and Sr (mainly <5 ppm), Th/U (0.06–2.35), Ti zircon temperature (617–1180 °C), ∑REE (total rare earth element) (98–1030 ppm), and Eu/Eu* (0.03 to <1.35) are predominant values for igneous crustal-derived zircons, with very few from mantle sources and of metamorphic origin. Crustal igneous zircons are mainly inherited grains crystallized in granitic magmas (with some charnockitic and tonalitic affinities) and a few from syenitic melts. Mantle zircons were crystallized in trace element depleted mantle source magmatic intrusion during crustal opening. Metamorphic zircons grown in sub-solidus solution in equilibrium with garnet “syn-metamorphic zircons” and in equilibrium with anatectic melts “anatectic zircons” during crustal tectono-metamorphic events. The U-Pb (3671 ± 23–612 ± 11 Ma) ages distinguish: Eoarchean to Neoproterozoic igneous zircons; Neoarchean to Mid Paleoproterozoic anatectic zircons; and Late Neoproterozoic syn-metamorphic grains. The Mesoarchean to Middle Paleoproterozoic igneous zircons are probably inherited from pyroxene-amphibole-bearing gneiss (TTGs composition) and amphibole-biotite gneiss, whose features are similar to those of the granites, granodiorites, TTG, and charnockites found in the Congo Craton, south Cameroon. The youngest igneous zircons could be grains eroded from Pan-African intrusion(s) found locally. Anatectic and syn-metamorphic zircons could have originated from amphibole-biotite gneiss underlying the zircon-gold bearing placers and from locally found migmatized rocks that are from the Cameroon mobile belt, which could be used as proxies for tracking gold.

中文翻译:

梅冈加含金沉积物南部(喀麦隆的阿达玛瓦)的南部至新元古代碎屑锆石:它们与泛非喀麦隆移动带和刚果克拉通的岩石紧密

通过激光烧蚀分流分析技术分析了Meiganga南部含金砂矿中碎屑锆石的核心,以确定其痕量元素丰度和U-Pb年龄。获得的数据用于表征每个晶粒,确定其形成条件,并试图追溯其出处。Hf(5980至12010 ppm),Y(27–1650 ppm),U(25–954 ppm),Th(8–674 ppm),Ti(2–256 ppm),Ta,Nb和Sr(主要< 5 ppm),Th / U(0.06-2.35),钛锆石温度(617-1180°C),∑REE(稀土元素总量)(98-1030 ppm)和Eu / Eu *(0.03至<1.35)是火成的地壳锆石的主要值,很少来自地幔来源和变质成因。地壳火成锆石主要是在花岗岩岩浆中结晶的遗传晶粒(具有一定的质性和tonalitic亲和力),而少数则来自于辉绿岩熔体。地壳开放期间,地幔锆石在贫化地幔元素源岩浆侵入中结晶。在地壳构造变质事件中,在亚固相线溶液中生长的变质锆石与石榴石“同型变质锆石”保持平衡,与无熔体熔体“过氧化锆石”保持平衡。U-Pb(3671±23–612±11 Ma)年龄区分:始新世至新元古代的火成锆石。新古宙至古元古代中古锆石;和晚新元古代同变质晶粒。中古元古代至中古元古代火成锆石可能来自辉石-斜方岩片麻岩(TTGs组成)和角闪石-黑云母片岩,其特征类似于喀麦隆南部刚果克拉通发现的花岗岩,花岗闪长岩,TTG和霞长岩。最年轻的火成锆石可能是从当地发现的泛非侵入物侵蚀而来的谷物。滑冰和同变质锆石可能起源于锆石含金砂岩下的角闪石-黑云母片麻岩以及喀麦隆移动带中的局部发现的浸蚀岩石,可以用作跟踪黄金的代理。
更新日期:2021-01-15
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