Petrological and zircon evidence for the Early Cretaceous granulite-facies metamorphism in the Dabie orogen, China
Petrological and zircon evidence for the Early Cretaceous granulite-facies metamorphism in the Dabie orogen, China
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中国大别造山带早白垩世麻粒岩相变质作用的岩石学和锆石证据
DOI：
10.1016/j.lithos.2017.03.024
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发表时间：
2017-07
期刊：
影响因子：
3.5
通讯作者：
Chen Yi-Xiang
中科院分区：
文献类型：
--
作者：
Gao Xiao-Ying;Zhang Qiang-Qiang;Zheng Yong-Fei;Chen Yi-Xiang
对大别造山带同生镁铁质麻粒岩和闪长岩进行了岩石学、矿物学、地球化学和年代学的综合研究。这些结果为碰撞造山带超高压变质岩的麻粒岩相改造提供了证据。麻粒岩中的锆石大多是新生的，其U-Pb年龄明显分为122~127 Ma和188 Ma±5.2 Ma两组。尽管这两组锆石具有相似的陡峭重稀土配分模式和可变的负Eu异常，但年轻组的U、Th和REE含量和Th/U比要比年长组高得多，εHf(T)值则低得多。这表明它们的生长与不同类型的脱水反应有关。较老的锆石区域含有石榴石+单斜辉石±石英的矿物包裹体，表明它们是在高压下通过变质反应生长的。相反，年轻的锆石区域只含有少量的石英包裹体，石榴石-单斜辉石-斜长石-石英压力计的压力为4.9~12.5kb。此外，单斜辉石-石榴石-铁-镁交换测温法测得的温度为738-951℃，因此，年轻的锆石微区在中低压力下可能是通过包晶反应生长的。较年轻的麻粒岩相变质年龄不仅与邻近闪长岩的年龄(125°±6.1 Ma)一致，而且与大别造山带中同时代镁铁质和长英质岩浆的大量侵位相一致。镁铁质麻粒岩及其邻近闪长岩矿物的δ~(18)O值均低于正常地幔，与大别造山带超高压榴辉岩相变质岩相似。结合主量元素和锆石Lu-Hf同位素组成，推测镁铁质麻粒岩的原岩与闪长岩的源岩相同，均为大陆俯冲通道板幔界面的镁铁质交代岩。该区早白垩世麻粒岩相变质岩的时空分布与碰撞后短短120~130 Ma的双峰式岩浆作用有关。这为碰撞造山带中的花岗岩、混合岩和岩浆岩与活动大陆裂谷之间的成岩作用提供了直接联系，从而将高热流从软流圈地幔转移到变薄的造山岩石圈进行部分熔融。
An integrated study of petrology, mineralogy, geochemistry, and geochronology was carried out for contemporaneous mafic granulite and diorite from the Dabie orogen. The results provide evidence for granulite-facies reworking of the ultrahigh-pressure (UHP) metamorphic rock in the collisional orogen. Most zircons from the granulite are new growth, and their U-Pb ages are clearly categorized into two groups at 122–127 Ma and 188 ± 2 Ma. Although these two groups of zircons show similarly steep HREE patterns and variably negative Eu anomalies, the younger group has much higher U, Th and REE contents and Th/U ratios, much lower εHf(t) values than the older group. This suggests their growth is associated with different types of dehydration reactions. The older zircon domains contain mineral inclusions of garnet + clinopyroxene ± quartz, indicating their growth through metamorphic reactions at high pressures. In contrast, the young zircon domains only contain a few quartz inclusions and the garnet-clinopyroxene-plagioclase-quartz barometry yields pressures of 4.9 to 12.5 kb. In addition, the clinopyroxene-garnet Fe-Mg exchange thermometry gives temperatures of 738–951 °C. Therefore, the young zircon domains would have grown through peritectic reaction at low to medium pressures. The younger granulite-facies metamorphic age is in agreement not only with the adjacent diorite at 125 ± 1 Ma in this study but also the voluminous emplacement of coeval mafic and felsic magmas in the Dabie orogen. Mineral separates from both mafic granulite and its adjacent diorite show uniformly lower δ18O values than normal mantle, similar to those for UHP eclogite-facies metaigneous rocks in the Dabie orogen. In combination with major-trace elements and zircon Lu-Hf isotope compositions, it is inferred that the protolith of mafic granulites shares with the source rock of diorites, both being a kind of mafic metasomatites at the slab-mantle interface in the continental subduction channel. The spatial and temporal distribution of Early Cretaceous granulite-facies metamorphic rocks in this region is associated with the bimodal magmatism within a short period of 120–130 Ma in the postcollisional stage. This provides a direct link in petrogenesis between the granulitic, migmatic and magmatic rocks in the collisional orogen to active continental rifting, whereby high heat flow was transferred from the asthenospheric mantle into the thinned orogenic lithosphere for partial melting.
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影响因子：
3.9
作者：
D. Cherniak
通讯作者：
D. Cherniak
DOI：
10.1007/978-3-319-78527-1
发表时间：
1973
期刊：
Stable Isotope Geochemistry
影响因子：
--
作者：
J. Hoefs
通讯作者：
J. Hoefs
影响因子：
3.9
作者：
F. Tomaschek;A. Kennedy;I. Villa;M. Lagos;C. Ballhaus
通讯作者：
F. Tomaschek;A. Kennedy;I. Villa;M. Lagos;C. Ballhaus
影响因子：
3.4
作者：
R. Zhang;J. Liou;Chin-Ho Tsai
通讯作者：
R. Zhang;J. Liou;Chin-Ho Tsai
影响因子：
5
作者：
D. Rubatto;J. Hermann
通讯作者：
D. Rubatto;J. Hermann