Using P-T paths to interpret the tectono thermal setting of prograde metamorphism an example fromthe northeastern
Using P-T paths to interpret the tectono thermal setting of prograde metamorphism an example fromthe northeastern
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利用P-T路径解释前变质作用的构造热背景——以东北地区为例
DOI：
10.1016/j.precamres.2010.12.002
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发表时间：
2011
影响因子：
3.8
通讯作者：
R.
中科院分区：
文献类型：
--
作者：
Forbes;C. J.;Giles;D.;Hand;M.;Betts;P. G.;Suzuki;K.;Chalmers;N.;and Dutch;R.
本文报道了南澳大利亚古中元古代伍兹山（Mount Woods Inlier）的一种斑生石榴石-堇青石-尖晶石岩浆岩的变质分析。岩石学分析与一系列P-T伪剖面相结合，表明由于早期卟啉岩心的生长和富铝、贫硅的化学环境的形成，有效体成分逐渐发生变化，为达到麻粒岩相条件提供了一条渐进路径的证据。红柱石卟卟母细胞被解释为在~ 2-3kbar和~ 550-610°C条件下的前变质作用的早期阶段生长。与早期进阶变质作用有关的地热梯度估计为~ 50-90°km−1。铝硅酸盐卟卟母细胞随后反应形成堇青石-尖晶石复合石，它们被早期形成的堇青石护城河从化学上限制了与大块岩石的剩余部分。峰变质作用在岩石学上以石榴石生长期为代表，达到了~ 4.7kbar和750°C的条件，相当于45-50°Ckm−1的地热梯度。Monazite CHIME分析得出月光山样品的年龄为~ 1615Ma，并被认为是在温度为~ 500-600°C的渐进变质过程中Monazite生长的。高峰变质作用与高勒克拉通（Fleurieu半岛）和澳大利亚东部元古代（如Broken Hill Block， Mount Isa Inlier）的高温/低压变质作用发生在1.61-1.59Ga。由于大量岩浆侵入地壳中上层，其中一些岩浆在挖掘和侵蚀过程中被移除，因此在低压条件下加热了Mount Woods Inlier。热岩随后被掩埋，此时达到了变质高峰。
We present metamorphic analysis from a porphyroblastic garnet–cordierite–spinel pelite from the Palaeo-Mesoproterozoic Mount Woods Inlier in South Australia. Petrographic analysis combined with a series of P–T pseudosections representative of a progressively changing effective bulk composition due to early porphyroblast growth and creation of an Al-rich, Si-poor chemical environment in the porphyroblast cores provides evidence of a prograde path that reached granulite facies conditions. Andalusite porphyroblasts are interpreted to have grown during the early phases of prograde metamorphism at conditions of ∼2–3kbar and ∼550–610°C. Geothermal gradients associated with early stages of prograde metamorphism are estimated to be ∼50–90°Ckm−1. The aluminosilicate porphyroblasts subsequently reacted to form cordierite–spinel symplectites that are chemically restricted from the remainder of the bulk rock by earlier formed cordierite moats. Peak metamorphism is petrographically represented by a phase of garnet growth, and attained conditions of ∼4.7kbar and 750°C, equivalent to a geothermal gradient of 45–50°Ckm−1. Monazite CHIME analysis has yielded an age of ∼1615Ma for the Moonlight Hills samples, and is suggested to represent monazite growth during prograde metamorphism through temperatures of ∼500–600°C. Peak metamorphism was contemporaneous with high-temperature/low-pressure metamorphism elsewhere in the Gawler Craton (Fleurieu Peninsula) and eastern Proterozoic Australia (e.g. Broken Hill Block, Mount Isa Inlier) at ca. 1.61–1.59Ga. The Mount Woods Inlier was heated at low pressure conditions due to intrusion of voluminous magmas to mid- to upper-crustal levels, some of which have been removed during exhumation and erosion. The hot rocks were then buried, at which point peak metamorphic conditions were attained.