Infiltration of prograde Cl-rich fluid into the granulitic continental crust from a collision zone in East Antarctica (Perlebandet, Sør Rondane Mountains)
Infiltration of prograde Cl-rich fluid into the granulitic continental crust from a collision zone in East Antarctica (Perlebandet, Sør Rondane Mountains)
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富含 Cl 的前流流体从南极洲东部的碰撞带渗透到粒状大陆地壳中（Perlebandet，S）
DOI：
10.1016/j.lithos.2016.12.028
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发表时间：
2017
期刊：
影响因子：
3.5
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Kawakami;T.;Higashino;F.;Skrzypek;E.;Satish-Kumar;M.;Grantham;G.;Tsuchiya;N.;Ishikawa;M.;Sakata;S.;Hirata;T.
利用泥质和长英质变质岩中含Cl黑云母的显微结构，将富Cl流体的入渗时间与东南极南龙格尔山脉（SRM）Perlebandet上部角闪岩-麻粒岩相变质岩的压力-温度-时间（P-T-t）路径进行了对比。显微结构观察表明，稳定的Al_2SiO_5多晶型由硅线石转变为蓝晶石+红柱石+硅线石，由地质温压法估算的P-T路径为逆时针P-T路径特征的SRM SW线。激光原位烧蚀电感耦合等离子体质谱法对石榴石中锆石包裹体进行U-Pb定年，结果表明：石榴子石、硅线石和富Cl黑云母（Cl > 0.4wt%）之间的包体-寄主关系表明，富Cl黑云母的形成是在硅线石稳定区的俯冲变质作用过程中进行的。这一过程可能早于部分熔融消耗黑云母（Cl = 0.1- 0.3wt%）。其次是逆行，中度含Cl的黑云母（Cl = 0.1-0.3重量%）取代石榴石。不同样品中富Cl黑云母形成的时间相似，各阶段共存流体的（H_2O）/f（HCl）值相似，这可以用富Cl流体的渗透来解释。流体存在的部分熔融在开始的变质作用可能有助于提高Cl浓度（和可能的盐度）的流体，和消耗的流体导致的脱水熔融的进展。逆行流体从结晶Cl-轴承部分熔体或外部衍生释放。Perlebandet的富Cl流体渗透大概发生在碰撞边界下盘的最上部。富Cl黑云母和角闪石沿着大规模剪切带和碎屑岩的局部分布支持了大陆碰撞期间富Cl流体通过构造边界的外部输入。
Utilizing microstructures of Cl-bearing biotite in pelitic and felsic metamorphic rocks, the timing of Cl-rich fluid infiltration is correlated with the pressure-temperature-time (P-T-t) path of upper amphibolite- to granulite-facies metamorphic rocks from Perlebandet, Sør Rondane Mountains (SRM), East Antarctica. Microstructural observation indicates that the stable Al2SiO5polymorph changed from sillimanite to kyanite + andalusite + sillimanite, andP-Testimates from geothermobarometry point to a counterclockwiseP-Tpath characteristic of the SW terrane of the SRM. In situ laser ablation inductively coupled plasma mass spectrometry for U–Pb dating of zircon inclusions in garnet yielded ca. 580 Ma, likely representing the age of garnet-forming metamorphism at Perlebandet.Inclusion-host relationships among garnet, sillimanite, and Cl-rich biotite (Cl > 0.4 wt%) reveal that formation of Cl-rich biotite took place during prograde metamorphism in the sillimanite stability field. This process probably predated partial melting consuming biotite (Cl = 0.1–0.3 wt%). This was followed by retrograde, moderately Cl-bearing biotite (Cl = 0.1–0.3 wt%) replacing garnet. Similar timings of Cl-rich biotite formation in different samples, and similarf(H2O)/f(HCl) values of coexisting fluid estimated for each stage can be best explained by prograde Cl-rich fluid infiltration. Fluid-present partial melting at the onset of prograde metamorphism probably contributed to elevate the Cl concentration (and possibly salinity) of the fluid, and consumption of the fluid resulted in the progress of dehydration melting. The retrograde fluid was released from crystallizing Cl-bearing partial melts or derived externally. The prograde Cl-rich fluid infiltration in Perlebandet presumably took place at the uppermost part of the footwall of the collision boundary. Localized distribution of Cl-rich biotite and hornblende along large-scale shear zones and detachments in the SRM supports external input of Cl-rich fluids through tectonic boundaries during continental collision.