Tectonic Environments of Cenozoic Volcanic Rocks in China and Characteristics of the Source Regions in the Mantle

Extensive volcanism is one of the important features of Cenozoic geology in China.Based on temporal-spatial distribution,the volcanism was associated with three major different geological settings:1)the continental rift basalts in Northeast and North China;2)the tension-fault basalts on the continental margins of Southeast China; and 3) the collision-zone high-K volcanics in the Qinghai-Xizang Plateau and its vicinities.The characteristics of “depletion in the south and enrichment in the north“of the China continental mantle are strongly supported by isotopic evidence.The Cenozoic continental cal characters,into the following geochemical provinces:1)the depleted mantle in South China;2)the primary mantle in Northeast and NorthChina; 3)the hybrid and transi-tional mantle in the region of Shandong ,Anhui,Jiangsu and northern Zhejiang;4)the depleted mantle around the Bohai Bay and the Lower Liaohe River;5)the K-metasomatic enriched mantle in the northern part of Northeast China;and 6)the re-cycled enriched mantle in the ancient subduction zone in the Qinghai-Xizang Plateau and its surround-ings.These geochemical characteristics on a regional scale must be a reflection of the nature of lithosphere evolution.

Tectonic environments of Cenozoic volcanic rocks in China and characteristics of the source regions in the mantle

Extensive volcanism is one of the important features of Cenozoic geology in China. Based on temporal-spatial distribution, the volcanism was associated with three major different geological settings: 1) the continental rift basalts in Northeast and North China; 2) the tension-fault basalts on the continental margins of Southeast China; and 3) the collision-zone high-K volcanics in the Qinghai-Xizang Plateau and its vicinities. The characteristics of “depletion in the south and enrichment in the north” of the China continental mantle are strongly supported by isotopic evidence. The Cenozoic continental mantle of China can be divided, on the basis of isotopic evidence and regionally geological characters, into the following geochemical provinces: 1) the depleted mantle in South China; 2) the primary mantle in Northeast and North China; 3) the hybrid and transitional mantle in the region of Shandong, Anhui, Jiangsu and northern Zhejiang; 4) the depleted mantle around the Bohai Bay and the Lower Liaohe River; 5) the K-metasomatic enriched mantle in the northern part of Northeast China; and 6) the re-cycled enriched mantle in the ancient subduction zone in the Qinghai-Xizang Plateau and its surroundings. These geochemical characteristics on a regional scale must be a reflection of the nature of lithosphere evolution.