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A unique period of bimodal volcanism at 130–110 Ma in the northern Sanandaj-Sirjan Zone: Evidence for an extensional setting
Lithos ( IF 2.9 ) Pub Date : 2021-04-13 , DOI: 10.1016/j.lithos.2021.106155
Bahman Rahimzadeh , Shahryar Mahmoudi , Fernando Corfu , Vahid Ahadnejad , Albrecht Von Quadt

The Sanandaj-Sirjan metamorphic-magmatic Zone (SaSZ) represents the Mesozoic active continental margin of the Neotethys Ocean between the Arabian plate and the Iranian plateau. The zone evolved at the margin of ancient Ediacaran basement, as documented in this paper with an age of 557 Ma for a trondhjemite. The Mesozoic activity of the SaSZ was most intense with sedimentation and magmatism in the Jurassic between 170 and 150 Ma, but this period was then followed by a 20 million years gap with almost no magmatic activity, which has been attributed to flat slab tectonics. The present paper is concentrated on the geochemistry, and zircon CA-ID-TIMS geochronology, of a bimodal, but mainly basaltic, volcanic and subordinate plutonic succession that represents the resumption of magmatism in a deep and gradually shallowing basin in the northern SaSZ between 130 and 110 Ma. The mafic to intermediate volcanic rocks are predominantly calc-alkaline and have εNd values of +0.3 to +3.9. The felsic volcanic rocks are dominantly high-K calc-alkaline with εNd values of −0.5 to +1.9. A suite of Cretaceous trondhjemites yields εNd values of −4.6 to −4.9. Together, the geochemical, lithological and geochronological indications suggest that the thick Barremian-Aptian bimodal magmatic suite represents magmatism in a continental arc to back-arc setting, controlled by extension and probably related to foundering of the flat slab and slab roll-back. These events initiated melting of the mantle in the northern SaSZ, heralding a period of extension and the subsequent development of ophiolites all along the Neothetyan suture.



中文翻译:

Sanandaj-Sirjan北部地区130-110 Ma的双峰火山爆发的独特时期:扩张性环境的证据

Sanandaj-Sirjan变质岩浆带(SaSZ)代表了阿拉伯板块与伊朗高原之间新特提斯海洋的中生界活跃大陆边缘。该区域在古代Ediacaran地下室的边缘演化,如本文所述,年龄为557 Ma的长白云母。SaSZ的中生界活动在侏罗纪的沉积和岩浆作用最强烈,发生在170至150 Ma之间,但随后这段时期是2000万年的缝隙,几乎没有岩浆活动,这归因于平板构造。本文主要研究双峰但主要是玄武岩的地球化学和锆石CA-ID-TIMS年代学。火山岩和次生岩体演替,代表了北萨尔茨堡州北部在130 Ma至110 Ma之间的一个逐渐深浅的盆地中的岩浆活动的恢复。镁铁质至中层火山岩主要为钙碱性且具有εNd值为+0.3至+3.9。长英质火山岩显性高K钙碱性与ε的Nd的-0.5到1.9的值。甲套件白垩纪trondhjemites产率ε的值的-4.6到-4.9。在一起的地球化学,岩性和年代学指示表明,厚的巴里米亚-阿普特双峰岩浆套件代表了大陆弧到背弧环境中的岩浆作用,受伸展作用控制,并且可能与平板的倒塌和平板的回滚有关。这些事件引发了北萨格勒布北部地幔的融化,预示着一段延伸期以及随后沿新山底缝合线形成的蛇绿岩的发展。

更新日期:2021-04-14
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