• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of South American earth sciences >Geochemistry of Jamari complex, central-eastern Rondonia: Andean-type magmatic arc and Paleoproterozoic crustal growth of the southwestern Amazonian Craton, Brazil
【24h】

Geochemistry of Jamari complex, central-eastern Rondonia: Andean-type magmatic arc and Paleoproterozoic crustal growth of the southwestern Amazonian Craton, Brazil

机译：中部隆多尼亚Jamari复杂区的地球化学：巴西西南亚马逊克拉通的安第斯型岩浆弧和古元古代地壳生长

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The Jamari complex (gabbro-diorite-tonalite/enderbite-granodiorite/charnoenderbite) represents a Paleoproterozoic (ca. 1.76-1.74 Ga) magmatic arc emplaced along the southwestern Amazonian Craton in central-eastern Rondonia, Brazil. Comprising metaplutonic and metasedimentary rocks, the Jamari complex constitutes the polydeformed Paleoproterozoic basement of Rondonia state. Together with regional data from the Rondonia-Juruena Province, our findings suggest that the southwestern border of the Amazonian Craton was the site of magmatic arc evolution from at least ca. 1.78 to 1.63 Ga. Elemental geochemical data show that intermediate/acid orthogneisses are metaluminous to mildly peraluminous, and have a medium to high-K, calc-alkaline signature, suggesting that they were formed in an immature Andean-type magmatic arc. Gabbros have signatures similar to tholeiites of active continental margin and diorites show characteristics compatible with rocks of tholeiite/calc-alkaline active continental margin volcanic arc. The chemical data of the Jamari complex felsic plutonic rocks show general trends of increasing contents of incompatible elements (K_2O, Rb, Nb, Th, La, Ba and Sr) and decreasing contents of compatible elements (Ni, V, Sc, MgO, Fe_2O_3, AI_2O_3, CaO and TiO_2) with increasing SiO_2. Although these variations are consistent with closed system fractional crystallization processes, the wide variation of Rb/ Zr, La/Sm, K/Rb, Nb/Y, Th/Y and Th/Yb in the felsic rocks may indicate random crustal contamination during the evolution of these rocks. Normalized trace element patterns show enrichment in LILEs (Rb, Ba, K, Th and Ce) relative to HFSEs (Nb, Zr, P and Ti) and are very similar to calc-alkaline subduction-related rocks from orogenic belts. The Jamari complex represents the western extension of similar metaplutonic rocks (Juruena Complex, Mato Grosso), occurring along some 500 km of the Paleoproterozoic Madeirinha orogen (1.78-1.63 Ga). During this event the rocks were metamorphosed under upper amphibolite to granulite facies conditions that only mildly disturbed their igneous characteristics. Zircon U-Pb crystallization ages (ID-TIMS, SHRIMP and LA-ICP-MS) set the acretional phase of the magmatic arc in Rondonia between 1.76 and 1.74 Ga. Metamorphic mineral paragenesis and textural features in these rocks, combined with geochronologic data, indicate that metamorphic conditions in the study area reached the granulite facies (T = ca. 750-800 ℃, P = 7 to 8 kbar) in a tectonothermal collisional event that occurred between 1.67 and 1.63 Ga. The Jamari complex in this region was subsequently reworked during the Rondonian-San Ignacio Orogeny (1.50-1.30 Ga), a tectonic episode characterized by crytical metamorphic mineral assemblages and anatexis, suggesting upper-amphibolite-facies metamorphism. The youngest tectonic event recognized in the Jamari complex is associated with tectonic reactivation, deformation, thermal overprint, and magmatism related to the Sunsas Orogeny (1.30-0.95 Ga). Its effects are represented by extensive development of shear zones (Ji-Parana system), mylonitic belts, rifts and sedimentary deposits, and post-collisional A-type intrusions.
机译：Jamari复杂体（辉闪闪长闪闪岩-辉长岩/ enderbite-granodiorite / charnoenderbite）代表古元古代（约1.76-1.74 Ga）岩浆弧，沿巴西东南部中部的亚马逊河克拉通西南部。 Jamari复合体包含准成岩和准沉积岩，构成了Rondonia州多变形的古元古代基底。结合来自Rondonia-Juruena省的区域数据，我们的发现表明，至少从大约20世纪30年代以来，亚马逊克拉通的西南边界是岩浆弧演化的地点。 1.78至1.63 Ga。元素地球化学数据显示，中度/酸性直生片麻岩属金属性至轻度铝质，并具有中等至高K的钙碱性特征，表明它们形成于不成熟的安第斯型岩浆弧中。长辉岩具有类似于活动大陆边缘的冲孔岩的特征，并且闪长岩显示出与冲孔岩/钙碱性活动大陆边缘火山弧的岩石相容的特征。 Jamari复杂长英质岩体的化学数据表明不相容元素（K_2O，Rb，Nb，Th，La，Ba和Sr）含量增加而相容元素（Ni，V，Sc，MgO，Fe_2O_3含量减少）的总体趋势，Al_2O_3，CaO和TiO_2）随着SiO_2的增加而增加。尽管这些变化与封闭的系统分步结晶过程一致，但长英质岩石中Rb / Zr，La / Sm，K / Rb，Nb / Y，Th / Y和Th / Yb的宽泛变化可能表明在该过程中地壳受到随机污染。这些岩石的演化。归一化的痕量元素模式显示相对于HFSE（Nb，Zr，P和Ti）的LILE（Rb，Ba，K，Th和Ce）富集，并且与造山带的钙碱性俯冲相关的岩石非常相似。 Jamari复合体代表了类似的古生代岩石（Juruena复合体，Mato Grosso）向西延伸，发生在古元古代Madeirinha造山带（1.78-1.63 Ga）中。在此事件中，岩石在上闪石下变质为花岗石相，仅轻度干扰了它们的火成岩特征。锆石的U-Pb结晶年龄（ID-TIMS，SHRIMP和LA-ICP-MS）将朗多尼亚岩浆弧的上升阶段设定在1.76和1.74 Ga之间。这些岩石的变质矿物共生作用和构造特征，再加上地质数据，结果表明，研究区的变质条件在1.67和1.63 Ga之间发生的构造热碰撞事件中达到了花岗石相（T = 750-800℃，P = 7至8 kbar）。在Rondonian-San Ignacio造山运动（1.50-1.30 Ga）期间进行了重做，这是一个构造性事件，其特征是冰晶变质矿物组合和后遗岩，表明上闪石相变质。 Jamari复合体中识别出的最年轻的构造事件与与Sunsas造山带（1.30-0.95 Ga）有关的构造再活化，变形，热套印和岩浆活动有关。它的作用表现为剪切带（Ji-Parana系统），Mylonitic带，裂谷和沉积物以及碰撞后的A型侵入带的广泛发展。

著录项

相似文献

  • 外文文献
  • 中文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号