Evidence of Gondwana early rifting process recorded by Resende-Ilha Grande Dike Swarm, southern Rio de Janeiro, Brazil
Evidence of Gondwana early rifting process recorded by Resende-Ilha Grande Dike Swarm, southern Rio de Janeiro, Brazil
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巴西里约热内卢南部 Resende-Ilha Grande Dike Swarm 记录的冈瓦纳早期裂谷过程的证据
DOI：
10.1016/j.jsames.2016.01.004
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发表时间：
2016
影响因子：
1.8
通讯作者：
P. Szatmari
中科院分区：
文献类型：
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作者：
E. Guedes;M. Heilbron;C. Valeriano;J. Almeida;P. Szatmari
陆相洪泛玄武岩和岩脉群的形成与整个地质时代的大陆分裂过程有关。位于巴西东南部的Resende - Ilha Grande岩脉群（RIGDS）与Gondwana碎裂有关，由侵入于前寒武纪片麻岩中的岩脉/岩台组成。堤防有三种明显的走向：偏北西向内陆；中部为NS-NNE向，海岸线为NE向，与前寒武纪构造线相一致。根据稀土、锶和钕同位素数据，该群由高tio2拉斑玄武岩组成，分为3套。Resende和Volta Redonda套房的初始87sr /86Sr比值较高，为0.7077 ~ 0.7065，而Angra dos Reis套房的初始87sr /86Sr比值为0.7066 ~ 0.7057。地球化学和同位素资料支持次大陆岩石圈地幔（SCLM）是高tio2玄武岩的主要来源。套间非均质性可以用前寒武纪地体中scm成分的不同和（或）不同程度的部分熔融和分块来解释。40Ar/39Ar数据表明，该群的年龄间隔约为156 - 144 Ma，比冈瓦纳破裂的平均年龄（约130-120 Ma）要老。年龄间隔将RIGDS置于Karoo岩浆活动（181 ~ 178 Ma）和Paraná-Etendeka岩浆活动（133 ~ 134 Ma）之间，表明超大陆在断裂之前受到了伸展作用的影响。
Continental flood basalts and dike swarm have been related to continental breakup process through geological time. The Resende – Ilha Grande Dike swarm (RIGDS) located in the southeast Brazil, is related the Gondwana breakup and composed of dikes/sills intruded in Precambrian gneiss. The dikes have three distinguish orientations: NNW more inland; NS-NNE in the central segment and NE orientation in the coast line, consistent with Precambrian structural lineaments. The swarm comprises high-TiO2tholeiitic basalts divided into three suites based on REE and Sr and Nd isotope data. The Resende and Volta Redonda suites present higher initial87Sr/86Sr ratios between 0.7077 and 0.7065, while Angra dos Reis suite presents values of 0.7066 to 0.7057. Geochemical and isotopic data support the sub-continental lithospheric mantle (SCLM) as the main source for the high-TiO2basalts. The suites heterogeneities are explained by different compositions of SCLM in accreted Precambrian terranes and/or different degree of partial melting and fractional.40Ar/39Ar data indicate age interval between ca. 156 to 144 Ma for the swarm, older than the average for Gondwana breakup (ca. 130-120 Ma). The age interval places the RIGDS between the Karoo magmatism (181-178 Ma) and the Paraná-Etendeka magmatism (133–134 Ma) and indicates that extensional process affected the supercontinent prior the break-up.
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