Jurassic segmentation of the early Andean magmatic Province in southern central Chile (35–39°S): Petrological constrains and tectonic drivers
Jurassic segmentation of the early Andean magmatic Province in southern central Chile (35–39°S): Petrological constrains and tectonic drivers
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智利中南部早期安第斯岩浆省的侏罗纪分段（南纬35-39°）：岩石学约束和构造驱动因素
DOI：
10.1016/j.lithos.2020.105510
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发表时间：
2020
期刊：
影响因子：
3.5
通讯作者：
K. Llanos
中科院分区：
文献类型：
--
作者：
P. Rossel;A. Echaurren;M. Ducea;P. Maldonado;K. Llanos
智利中南部（35°-39 ° S）侏罗纪火山活动主要有两个单元。第一个以位于实际海岸山脉（35°-35 ° 30 ′S）的阿尔托斯de Hualmapu组的火山岩和次火山岩为主的安山质沉积物为特征，第二个对应于位于实际主山脉（39°S）的Nacientes del Biobio组的下部玄武岩和上部安山质至英安质上部段。这两个单位标志着北方和巴塔哥尼亚早期安第斯岩浆省（EAMP），达到最大的岩浆活动在这方面的晚中侏罗世在沿海科迪勒拉，两个小脉冲的活动之间的上三叠世和下侏罗纪之间的过渡。在155 Ma之后，该地区没有记录到弧活动的证据，当时火山轴似乎转移到实际的主科迪勒拉，直到下白垩纪，当它再次向西恢复时。弧锋的不连续性表明在轴向存在一个主要的截止点，在36-37°。全岩地球化学和Sr-Nd-Pb同位素数据表明，这种区域性不连续性与岩浆的富集相一致，表明富集源在岩浆成因中的参与率为20-30%。由于在侏罗纪和早白垩世期间，冈瓦纳西部的构造体制主要是张性到张性的，因此不像在浅层假设高度同化，因此观察到的富集应该反映了由于上三叠世和中侏罗世期间巴塔哥尼亚弧下的海洋板块的大规模回滚和撕裂而被板片拖曳的肥沃软流圈地幔的增加。
Jurassic volcanismin Southern-Central Chile (35°–39°S) is represented mainly by two units. The first characterized by the volcanic and subvolcanic mostly andesitic deposits of the Altos de Hualmapu Formation, located in actual Coastal Cordillera (35°–35°30′S) and the second corresponding to the lower basaltic and upper andesitic to dacitic upper member of Nacientes del Biobio Formation, in actual Main Cordillera (39°S). Both units mark the transition between northern and patagonian segments of Early Andean Magmatic Province (EAMP) that reach its maximum magmatic activity in this area during late Middle Jurassic in Coastal Cordillera, after two minor pulses of activity between Upper Triassic and Lower Jurassic. No evidence of arc activity is recorded in this area after 155 Ma, when volcanic axis seems to shift to actual Main Cordillera until Lower Cretaceous when it is resumed again to the west. The discontinuity of the arc front suggest the presence of a major cutoff in axis at ≈36–37°. Whole rock geochemical and isotopical Sr-Nd-Pb data shows that this areal discontinuity coincides with an enrichment of the magmas that suggest ≈20–30% of participation of an enriched source in the genesis of the magmas. Given the mostly extensional to transtensional tectonic regime of Western Gondwana during Jurassic and Lower Cretaceous it is unlike to assume high degrees of assimilation at shallow levels, so the observed enrichment should reflect the addition of fertile asthenospheric mantle dragged by the slab as result of the massive roll back and tearing of the oceanic plate under the Arc in Patagonia during Upper Triassic and Middle Jurassic.
智利中北部（南纬31â32°）侏罗纪至早白垩世增生后左旋扭扭
影响因子：
2.3
作者：
Willner;Richter
通讯作者：
Richter