Petrogenesis of the Neoproterozoic Peraluminous Orogenic Granite and Tertiary Phonolites from Jabal Fezzan in Southern Libya

IF 1 4区 地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS
Ali S. Bensera
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Abstract

The majority of Neoproterozoic rocks exposed in southern Libya, are comprised of intrusive coarse-grained porphyritic, two-mica, and high K-calc alkaline granite. The Jabal Fezzan Granite (JFG) is located in southwestern Libya. In this study, trace elements and whole-rock geochemistry have been used to understand the origin and the process of petrogenesis of the studied granites. The JFG is high-Si, Rb, Y, Nb, and (ASI values greater than 1.1). Mineralogically, it is characterized by the presence of minor muscovite and biotite and a lack of hornblende, exhibiting features of S-type granites, and having a character that belongs to an alkali-calcic series. According to geochemical value, light REE-enriched, characterized by moderate enrichments in LREE (La/Sm), HREE, and weak negative Eu-anomalies. The geochemical modeling of the (JFG) reveals that the JFG derived from the melting of the crust and underwent high fractional crystallization (~50%) of plagioclase and K-feldspar at (H-P) conditions (750–980°C/1–4 GPa). The Jabal Fezzan (JFG) formed during Pan-African orogenic events during the destabilization of the interior Saharan metacraton due to compression stress and transpressive movements along pre-existing weakness and reactivation of shear zones inherited from Paleoproterozoic evolution. The Neoproterozoic basement forms the northernmost margin of the intracratonic Muruzq Basin, as evidenced by (greenschist facies) and intruded granitic rocks derived at the syn-collision stage (630–540 Ma).

Abstract Image

Abstract Image

利比亚南部 Jabal Fezzan 新新生代白铝造山花岗岩和第三纪辉绿岩的岩石成因
摘要利比亚南部出露的新新生代岩石大多由侵入性粗粒斑岩、双云母和高钾钙碱性花岗岩组成。Jabal Fezzan 花岗岩(JFG)位于利比亚西南部。本研究采用微量元素和全岩地球化学方法来了解所研究花岗岩的成因和岩石成因过程。JFG 属于高硅、高铷、高钇、高铌和(ASI 值大于 1.1)花岗岩。在矿物学上,它的特征是含有少量的黝帘石和斜长石,缺乏角闪石,表现出 S 型花岗岩的特征,具有属于碱钙质系列的特征。根据地球化学值,富含轻度 REE,其特征是 LREE(La/Sm)、HREE 中度富集,Eu 负异常较弱。JFG的地球化学模型显示,JFG源于地壳熔融,在(H-P)条件下(750-980°C/1-4 GPa)经历了斜长石和K长石的高分化结晶(约50%)。Jabal Fezzan(JFG)是在泛非造山运动中形成的,当时撒哈拉内部的元古宙由于压缩应力和沿原已存在的薄弱剪切带的转位运动以及古新生代演化过程中遗留下来的剪切带的重新激活而导致内部不稳定。新元古代基底构成了地壳内穆鲁兹克盆地的最北缘,其证据是在同步碰撞阶段(630-540Ma)衍生的(绿泥石面)和侵入花岗岩石。
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来源期刊
Petrology
Petrology 地学-地球科学综合
CiteScore
2.40
自引率
20.00%
发文量
27
审稿时长
>12 weeks
期刊介绍: Petrology is a journal of magmatic, metamorphic, and experimental petrology, mineralogy, and geochemistry. The journal offers comprehensive information on all multidisciplinary aspects of theoretical, experimental, and applied petrology. By giving special consideration to studies on the petrography of different regions of the former Soviet Union, Petrology provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.
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