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首页> 外文期刊>Journal of South American earth sciences >Geochemistry and origin of the early Mesoproterozoic mangerite-charnockite- rapakivi granite association of the Serra da Providencia suite and associated gabbros, central-eastern Rondonia, SW Amazonian Craton, Brazil
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Geochemistry and origin of the early Mesoproterozoic mangerite-charnockite- rapakivi granite association of the Serra da Providencia suite and associated gabbros, central-eastern Rondonia, SW Amazonian Craton, Brazil

机译：巴西西南部隆多尼亚中东部的Serra da Providencia套件的中元古生代锰铁矿-霞石-rapakivi花岗岩协会和相关的辉长岩的地球化学和成因

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摘要

The Serra da Providencia suite (SPS) is constituted of quartz mangerite-charnockite-rapakivi granite and coeval mafic rocks, intruded during the 1.60-1.53 Ga interval into Paleoproterozoic metamorphic basement (Jamari Complex) in the Juruena-Rondonia geochronologic province, SW Amazonian Craton. In this region the Serra da Providencia suite consists of two batholiths and several small plutons repre-sented by syeno-monzogranites and igneous quartz mangerite and charnockites. The Serra da Providencia granites are ferroan, calc-alkalic to alkali-calcic and characterized by high Na_2O + K_2O, Rb, Zr, Y, Nb, Ta, Ce, Zn, Ga, and REE (except for Eu), moderate Ba, and low Sr, MgO, and CaO. Ga/Al, Y/Nb, FeO_T/(FeO_T + MgO) and K_2O/Na_2O ratios are high and Sr/Ba and Rb/Ba are low and are geochemically similar to typical A2-subtype granites. The SPS charnockites and quartz mangerites display values of FeOr, MgO, CaO, Ba, Rb, Sr, Nb/Ta and Zr/Hf similar to the SPS A-type granites. The occurrence of magnetite as an accessory phase and the high FeOT/(FeO_T + MgO) in granites, charnockites and quartz mangerites suggest crystallization from a relatively oxidized magma and also explain the occurrence of titanite as a primary phase in these granites, similar to those reported in several localities of the Amazonian Craton. The parental magma of the mafic rocks of the SPS probably had mainly enriched sources and resulted from melting of heterogeneous mantle reservoirs with coherent chemical characteristics. Trace elements data indicate subduction-modified mantle sources for the mafic rocks that are in agreement with the post-collisional character of this magmatism. A large set of whole-rock Sm-Nd isotope data (Bettencourt et al., 1999; Scandolara, 2006; Santos et al., 2008 and this work) demonstrate that granites, charnockites and quartz mangerites of the study area are the product of magmas derived from interaction between enriched mantle derived magmas (in very subordinate proportions) and recycled crust in larger proportion. The source region is dominated by Paleoproterozoic material, but several samples yield Archaean model ages that are the first evidence for such ancient source materials in the SW Amazonian Craton. The Serra da Providencia suite was emplaced during the post-collisional stage of the Juruena-Jamari arc and Madeirinha orogeny (Scandolara et al., 2011), and post-dates the collision between the Tapajos (Tapajos-Parima geochronological province, Para, Brazil) and Bolivia (palaeocontinent which precedes Sunsas geochronological province) blocks. Its geochemical and structural features are coincident with those recognized in post-collisional granitoids. Geochemical data suggest that complex processes which involved crustal melting, fractional crystalli-zation, magma mixing and, in some extent, crustal assimilation were responsible for the magmatism of the Serra da Providencia suite. The magmas that constitute the Serra da Providencia suite resulted from varying degrees of partial melting of a compositionally heterogeneous source. The nature of the source and the degree of melting exerted a significant control over compositional variation in some of the parental magmas which were also affected by subsequent fractional crystallization and mingling pro-cesses. Internal variations in composition observed in several bodies can be the result of incremental amalgamation of different magma pulses that varied mainly in the degree of partial melting.
机译：Serra da Providencia套房（SPS）由石英马格石-霞石-rapakivi花岗岩和中世纪的镁铁质岩石组成，在1.60-1.53​​ Ga间隔内侵入到Juruena-Rondonia年代学省西南亚马逊古克拉通的古元古代变质基底（Jamari Complex）中。 。在该地区，Serra da Providencia套房包括两个蜡基岩和几个小潘氏岩体，它们由同辉辉石花岗岩，火成的石英锰铁矿和方沸石组成。普罗维登西亚山脉的花岗岩为亚铁，钙碱性至钙碱性，其特征为高Na_2O + K_2O，Rb，Zr，Y，Nb，Ta，Ce，Zn，Ga和REE（Eu除外），中等Ba，以及低的Sr，MgO和CaO。 Ga / Al，Y / Nb，FeO_T /（FeO_T + MgO）和K_2O / Na_2O的比率高，而Sr / Ba和Rb / Ba的比率低，并且在地球化学上类似于典型的A2亚型花岗岩。与SPS A型花岗岩相似，SPS霞石和石英quartz石显示的FeOr，MgO，CaO，Ba，Rb，Sr，Nb / Ta和Zr / Hf值。花岗岩，菱锰矿和石英锰铁矿中磁铁矿作为副相的存在和高FeOT /（FeO_T + MgO）的存在暗示着从相对氧化的岩浆中结晶，也解释了钛铁矿作为这些花岗岩中的主要相的发生。在亚马逊克雷顿州的几个地方都有报道。 SPS镁铁质岩体的母岩浆可能主要是富集的来源，是由于具有相干化学特征的非均质地幔储层融化所致。痕量元素数据表明，镁铁质岩的俯冲修饰地幔源与这种岩浆作用的碰撞后特征一致。大量的全岩石Sm-Nd同位素数据（Bettencourt等，1999； Scandolara，2006； Santos等，2008和这项工作）表明，研究区的花岗岩，霞石岩和石英锰铁矿是该区域的产物。富集地幔衍生岩浆（比例非常低）与回收地壳之间的相互作用所产生的岩浆。源区以古元古代材料为主，但一些样品产生了古生代模型年龄，这是西南亚亚马逊克拉通这种古老源材料的第一个证据。 Serra da Providencia套件是在Juruena-Jamari弧和Madeirinha造山运动的碰撞后阶段（Scandolara等，2011）放置的，并在Tapajos（Tapajos-Parima地质年代省，巴西帕拉）之间发生碰撞后进行了定位。 ）和玻利维亚（在Sunsas年代学省之前的古大陆）区块。它的地球化学和结构特征与碰撞后的花岗岩类一致。地球化学数据表明，涉及地壳融化，部分结晶，岩浆混合以及在某种程度上地壳同化的复杂过程是造成Serra da Providencia组岩浆作用的原因。构成Serra da Providencia套件的岩浆是由于成分异质源的部分熔融程度不同而引起的。源的性质和熔化程度对某些母体岩浆中的成分变化起了重要的控制作用，这些母质岩浆也受到随后的分步结晶和混合过程的影响。在几个物体中观察到的成分内部变化可能是不同岩浆脉冲逐渐合并的结果，这些岩浆脉冲主要在部分熔融的程度上发生变化。

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