SOME ISOTOPIC CONSTRAINTS ON THE EVOLUTION OF THE GRANULITE AND UPPER AMPHIBOLITE FACIES TERRANES IN THE EASTERN MUSGRAVE BLOCK, CENTRAL AUSTRALIA
SOME ISOTOPIC CONSTRAINTS ON THE EVOLUTION OF THE GRANULITE AND UPPER AMPHIBOLITE FACIES TERRANES IN THE EASTERN MUSGRAVE BLOCK, CENTRAL AUSTRALIA
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DOI：
10.1016/0301-9268(94)00060-5
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发表时间：
1995-02-01
影响因子：
3.8
通讯作者：
FANNING, CM
中科院分区：
文献类型：
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作者：
CAMACHO, A;FANNING, CM
澳大利亚中部马斯格雷夫地块的中东部由中新元古代的Fallon和Mulga Park子域组成，它们被称为Woodroffe逆冲断层的糜棱岩和假玄武玻璃岩区隔开，这些子域以前被认为经历了不同的地质历史，但差异主要与变质等级有关。其中，Festival亚域至少达到了过渡麻粒岩相变质条件，Mulga Park亚域达到了上角闪岩相变质条件。长英质片麻岩从Festival和Mulga公园子域包含锆石的自形中心过度生长的圆形细长边缘结构。离子探针U-Pb分析结果分别为1557 +/- 24和1554 +/- 28 Ma，并被解释为代表了岩浆结晶的时间。这些年龄对片麻岩前体的沉积或侵位有最大的年龄限制。高级变质作用发生在1200 ~ 1150 Ma之间，在1150 Ma左右侵入几个花岗岩类岩套之前，变质作用从上部角闪岩相逐渐过渡到麻粒岩相。Fengten次域的Kulgera二长花岗岩和Ayers Ranges二长花岗岩类岩套分别获得1150 +/- 12和1152 +/- 11 Ma的离子探针U-Pb结晶年龄。对艾尔斯岭的二长花岗岩进行一致的U-Pb同位素稀释分析，得到更精确的年龄为1152 +/- 3 Ma。侵入Mulga Park次区域的斑状岩套的离子探针U-Pb岩浆年龄为1159 +/- 20 Ma。这些侵位年龄表明，广泛的格伦维尔式长英质岩浆活动，以前没有在澳大利亚承认。伍德罗夫冲断形成期间，大量的地壳缩短，彼得曼造山运动（类似于550马），当Festival Subdomain被推到Mulga公园Subdomain。同运动学白云母和黑云母记录了560 ~ 520 Ma的K-Ar和Rb-Sr年龄。由于应变和相关矿物重结晶局限于下伏的Mulga Park子域，因此在February子域没有记录到Petermann事件。我们认为，在Petermann造山运动之前，麻粒岩没有暴露。因为阿玛迪斯盆地的基底石英岩只出现在角闪岩相的Mulga Park子域上。
The central to eastern Musgrave Block, central Australia, consists of the Meso- to Neoproterozoic Fregon and Mulga Park subdomains that are separated by a zone of mylonites and pseudotachylytes known as the Woodroffe Thrust, The subdomains were previously considered to have undergone different geological histories, but the differences relate mainly to metamorphic grade. The Fregon Subdomain attained at least transitional granulite facies metamorphic conditions and the Mulga Park Subdomain reached upper amphibolite facies. Felsic gneisses from both the Fregon and Mulga Park subdomains contain zircons that are structured with euhedral centres overgrown by round elongate rims. Ion-microprobe U-Pb analyses of the cores yield ages of 1557 +/- 24 and 1554 +/- 28 Ma, respectively, and are interpreted to represent the time of igneous crystallization. These ages place a maximum age constraint on the deposition or emplacement of the gneiss precursor.High-grade metamorphism, grading from upper amphibolite to granulite facies, took place between 1200 and 1150 Ma and prior to the intrusion of several granitoid suites at around 1150 Ma. The Kulgera Adamellite and Ayers Ranges Adamellite granitoid suites of the Fregon Subdomain yield ion-microprobe U-Pb crystallization ages of 1150 +/- 12 and 1152 +/- 11 Ma, respectively. A concordant U-Pb isotope dilution analysis on the Ayers Ranges Adamellite yields a more precise age of 1152 +/- 3 Ma. The porphyritic suite intruding the Mulga Park Subdomain yield an ion-microprobe U-Pb magmatic age of 1159 +/- 20 Ma. These emplacement ages indicate extensive Grenvillian felsic magmatism not previously recognized in Australia.The Woodroffe Thrust formed during a period of substantial crustal shortening, the Petermann Orogeny (similar to 550 Ma), when the Fregon Subdomain was thrust onto the Mulga Park Subdomain. Synkinematic muscovite and biotite record K-Ar and Rb-Sr ages between 560 and 520 Ma, This Petermann event is not recorded in the Fregon Subdomain due to confinement of the strain and associated mineral recrystallization to the underlying Mulga Park Subdomain, We suggest that the granulites were not exposed prior to the Petermann Orogeny, as the basal quartzites of the Amadeus Basin occur only on the amphibolite facies Mulga Park Subdomain.