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首页> 外文期刊>Journal of South American earth sciences >Peraluminous leucogranites of the Cordilheira Suite: A record of Neoproterozoic collision and the generation of the Pelotas Batholith, Dom Feliciano Belt, Southern Brazil
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Peraluminous leucogranites of the Cordilheira Suite: A record of Neoproterozoic collision and the generation of the Pelotas Batholith, Dom Feliciano Belt, Southern Brazil

机译：Cordilheira套件中的高铝白云石花岗岩：新元古代碰撞记录和Pelotas岩床的形成，巴西南部Dom Feliciano带

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The Cordilheira Suite is comprised of peraluminous granites that constitute, together with the Quiteria granite, the beginning of the formation of the Pelotas Batholith in the central portion of the Dom Feliciano Belt. The batholith is composed of seven granitic suites with minor occurrences of gabbro, diorite and subvolcanic rocks. Its evolution between 650 and 550 million years ago is characterised by a ranging from metaluminous to peraluminous rocks and from calc-alkaline to alkaline and peralkaline series. The Cordilheira Suite is composed of the Cordilheira, Arroio Francisquinho, Butia and Tres Fi-gueiras granites, which contain muscovite and/or biotite, with the following accessory minerals: tourmaline, garnet, sillimanite, apatite, zircon, monazite and ilmenite. The granitic bodies are elongate; their ascent and emplacement were controlled by high-angle shear zones oriented at N45-70°E. They have mylonitic structures with magmatic foliation accompanied by a low-angle stretching lineation, indicating that these bodies were emplaced under syn-kinematic conditions during a transcurrent event. The granites have high-K calc-alkaline affinity and are peraluminous. The LILE and REE contents are low. The K_2O/Na_2O and CaO/Na_2O ratios are approximately 1 and less than 0.3, respectively. Pseudosections calculated using the Perple X program suggests that the granites were formed at partial melting temperatures between 740 and 820 °C and pressure between 8.5 and 9 kbar. Petrographic and chemical data suggest that the magmas were generated by the partial melting of the migmatitic pelitic gneisses of the Varzea do Capivarita Complex and, to a lesser degree, orthogneisses of the Arroio dos Ratos Complex, which left a granulitic residue. UHT conditions of granulite facies metamorphism were recorded in the Varzea do Capivarita paragneisses by mineral paragenesis and indicate that temperatures between 900 and 1000 °C and pressures between 4 and 8 kbar were required for the partial melting. It is likely that these medium-pressure conditions resulted from the thickening of the continental crust when the Rio de La Plata Craton collided with the Kalahari Craton to form southwestern Gondwana at the end of the Neoproterozoic.
机译：Cordilheira Suite由高铝质花岗岩组成，与Quiteria花岗岩一起构成了Dom Feliciano Belt中部Pelotas岩基的开始。岩床由七个花岗岩组组成，少量出现辉长岩，闪长岩和次火山岩。它在650至5.5亿年前的演变过程中，其特征是从金属矿到高铝岩，从钙碱性到碱性和高碱性系列。 Cordilheira套房由Cordilheira，Arroio Francisquinho，Butia和Tres Fi-gueiras花岗岩组成，这些花岗岩含有白云母和/或黑云母以及以下辅助矿物：电气石，石榴石，硅线石，磷灰石，锆石，独居石和钛铁矿。花岗岩体是细长的。它们的上升和就位由N45-70°E定向的高角度剪切带控制。它们具有带岩浆叶的淀粉状结构，并伴有低角度的伸展线，表明这些物体在跨流事件中处于同运动条件下。花岗岩具有高K钙碱性亲和力，并且是高铝质的。 LILE和REE含量低。 K_2O / Na_2O和CaO / Na_2O之比分别约为1和小于0.3。使用Perple X程序计算的伪截面表明，花岗岩是在740至820°C的部分熔融温度和8.5至9 kbar的压力下形成的。岩石学和化学数据表明，岩浆是由Varzea do Capivarita Complex的多壁胶质片麻岩和部分Arroio dos Ratos Complex的正片麻岩的部分融化而产生的，这留下了粒状残余物。通过矿物共生在Varzea do Capivarita paragneisses中记录了花岗石相变质的UHT条件，表明部分熔化需要900至1000°C的温度和4至8 kbar的压力。这些中压条件很可能是里约热内卢拉普拉塔克拉通与卡拉哈里克拉通相撞形成新元古代末西南冈瓦纳时大陆壳增厚的结果。

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