利比亚Gharyan火山省晚新生代玄武岩地球化学及40Ar/39Ar年龄

IF 1 4区 地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY
Abdelmoniem Masoud, Abdelsalam Elshaafi, Özgür Karaoğlu, Alsedik Abousif, Michele Lustrino
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引用次数: 0

摘要

新生代Gharyan火山省(GVP)是利比亚四个主要火成岩区之一,面积约4500平方公里。尽管GVP的位置靠近的黎波里西北部的主要人口中心,但关于这种岩浆活动起源的研究数量相对有限。在此,我们讨论了全岩地球化学数据,并提出了一个新的矿物化学和40Ar/39Ar的玄武岩年代学研究。文献中确定的两种类型的玄武岩(定义为“高原”和“晚期”玄武岩)的矿物学和地球化学差异不能与共同母岩浆的分离结晶有关。这两组玄武岩可以更好地解释为来自同一地幔源的液体,经历了不同程度的部分熔融,晚期玄武岩代表了较低程度的熔融萃取,没有地壳污染的迹象。微量元素约束条件支持在~70 ~ 90 km深度处接近尖晶石-石榴石过渡的非均质岩石圈地幔的~2 ~ ~12%部分熔融成因。Gharyan玄武岩的微量元素和Sr-Nd同位素组成与利比亚中部(如Al Haruj火山省)和意大利南部(如Etna和Pantelleria)的其他新生代火山岩重叠,缺乏北非其他新生代玄武岩省所发现的富集地幔成分。新的高精度40Ar/39Ar年龄测定表明,两个玄武岩熔岩系列的喷发年龄大致同步,大部分在5.4 ~ 3.8 Ma范围内,高原玄武岩的喷发年龄在统计上略早于晚期,但有较大的重叠。岩脉的年代测定至~28 Ma,表明存在一个更古老的渐新世火山阶段,其产物几乎完全被侵蚀。本次研究报告的最年轻年龄表明火山活动一直持续到上新世晚期(2.67 Ma)。“高原”玄武岩与“晚期”玄武岩的40Ar/39Ar年龄重叠表明,应重新考虑两个不同火山阶段的存在。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Geochemistry and 40Ar/39Ar ages of late Cenozoic basaltic rocks from Gharyan Volcanic Province, NW Libya
The Cenozoic Gharyan volcanic province (GVP) represents one of the four major igneous districts of Libya, spreading over an area of ~4,500 km2. Despite the location of GVP close to major population centres in northwest Tripoli, the number of studies on the origin of this magmatism is relatively limited. Here, we discuss whole-rock geochemical data and present a new mineral chemistry and a 40Ar/39Ar geochronology study of the basaltic rocks of GVP. The mineralogical and geochemical differences of the two types of basalts identified in literature, definedas “plateau” and “late” basalts cannot be related to fractional crystallisation of a common parent magma. The two groups of basaltic rocks are better interpreted as liquids generated from the same mantle source experiencing different degrees of partial melting, with the late-stage basalts representing lower degrees of melt extraction, without indication of crustal contamination. Trace element constraints support an origin from~2 to ~12% partial melting of a heterogeneous sub-lithospheric mantle close to the spinel-garnet transition at ~70-90 km depth.Trace elements and Sr-Nd isotopic compositions of the Gharyan basaltic rocks overlap the other Cenozoic volcanic rocks of central Libya (e.g., Al Haruj volcanic province) and southern Italy (e.g., Etna and Pantelleria), lacking the presence of the enriched mantle component identified in other North African Cenozoic basaltic provinces. The new high precision 40Ar/39Ar age determinations indicate roughly simultaneous eruption ages of the two basaltic lava series, mostly in the 5.4-3.8 Ma range, with plateau basalts being statistically slightly older than the late stage, but with a large overlap. The dating of a dyke to ~28 Ma indicates the presence of an older Oligocene volcanic phase, whose products have been almost entirely eroded. The youngest age reported in this study indicates that volcanic activity continued until latest Pliocene (2.67 Ma). The overlap of 40Ar/39Ar ages between “plateau” and“late” basalts indicates that the existence of two distinct volcanic phases should be reconsidered.
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来源期刊
Italian Journal of Geosciences
Italian Journal of Geosciences GEOSCIENCES, MULTIDISCIPLINARY-
CiteScore
2.90
自引率
11.10%
发文量
25
审稿时长
>12 weeks
期刊介绍: The Italian Journal of Geosciences (born from the merging of the Bollettino della Società Geologica Italiana and the Bollettino del Servizio Geologico d''Italia) provides an international outlet for the publication of high-quality original research contributions in the broad field of the geosciences. It publishes research papers, special short papers, review papers, discussion-and-replies for their rapid distribution to the international geosciences community. The journal is firstly intended to call attention to the Italian territory and the adjacent areas for the exceptional role they play in the understanding of geological processes, in the development of modern geology and the Earth sciences in general. The main focus of the journal is on the geology of Italy and the surrounding sedimentary basins and landmasses, and on their relationships with the Mediterranean geology and geodynamics. Nevertheless, manuscripts on process-oriented and regional studies concerning any other area of the World are also considered for publication. Papers on structural geology, stratigraphy, sedimentology, basin analysis, paleontology, ecosystems, paleoceanography, paleoclimatology, planetary sciences, geomorphology, volcanology, mineralogy, geochemistry, petrology, geophysics, geodynamics, hydrogeology, geohazards, marine and engineering geology, modelling of geological process, history of geology, the conservation of the geological heritage, and all related applied sciences are welcome.
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