Major and trace element and Sr-Nd-Hf-Pb isotopic data for the most primitive Tertiary lavas from the Veneto region (South-Eastern Alps, Italy) show the typical features of HIMU hotspot volcanism, variably diluted by a depleted asthenospheric mantle component (Sr-87/Sr-86(i) = 0.70306-0.70378; epsilon(Ndi) = +3.9 to + 6.8; epsilon(Hfi) = + 6.4 to + 8.1, Pb-206/Pb-204(i) = 18.786-19.574). P-wave seismic tomography of the mantle below the Veneto region shows the presence of low-velocity anomalies at depth, which is consistent with possible upwellings of plume material. Between the depths of 100-250 km the velocity anomalies are approximately 2-2.5% slower than average, implying a temperature excess of about 220-280 K, in agreement with estimates for other mantle plumes in the world. In this context, the Veneto volcanics may represent the shallow expression of a mantle upflow. The presence of a HIMU-DM component in a collision environment has significant geodynamic implications. Slab detachment and ensuing rise of deep mantle material into the lithospheric gap is proposed to be a viable mechanism of hotspot magmatism in a subduction zone setting.
Geodynamic implications of deep mantle upwelling in the source of Tertiary volcanics from the Veneto region (South-Eastern Alps)
MACERA, PATRIZIA;
2003-01-01
Abstract
Major and trace element and Sr-Nd-Hf-Pb isotopic data for the most primitive Tertiary lavas from the Veneto region (South-Eastern Alps, Italy) show the typical features of HIMU hotspot volcanism, variably diluted by a depleted asthenospheric mantle component (Sr-87/Sr-86(i) = 0.70306-0.70378; epsilon(Ndi) = +3.9 to + 6.8; epsilon(Hfi) = + 6.4 to + 8.1, Pb-206/Pb-204(i) = 18.786-19.574). P-wave seismic tomography of the mantle below the Veneto region shows the presence of low-velocity anomalies at depth, which is consistent with possible upwellings of plume material. Between the depths of 100-250 km the velocity anomalies are approximately 2-2.5% slower than average, implying a temperature excess of about 220-280 K, in agreement with estimates for other mantle plumes in the world. In this context, the Veneto volcanics may represent the shallow expression of a mantle upflow. The presence of a HIMU-DM component in a collision environment has significant geodynamic implications. Slab detachment and ensuing rise of deep mantle material into the lithospheric gap is proposed to be a viable mechanism of hotspot magmatism in a subduction zone setting.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
