Zircon ages and geochemistry are presented for igneous rocks from SW Vietnam and S Cambodia. Four main age groupings occur: Cretaceous (107-75 Ma), Early Jurassic (195 Ma), Late Triassic (230-222 Ma), and Permian (294-265 Ma). Cretaceous and Jurassic samples are amphibole-bearing biotite granodiorites to biotite granites and occur mainly east of the Kampot Fold Belt. Pre-Cretaceous samples occur within the Kampot Fold Belt and are dominantly felsic volcanics. The rocks are primarily high-K calc-alkaline, weakly peraluminous rhyolites or granites, with similar arc-like trace element patterns. Cretaceous granites are similar to Dalat Zone Granites and formed during Pacific subduction. Two Cretaceous granites have adakite-like signatures. The youngest Cretaceous granite has an A-type signature and may represent post-collision activity following the cessation of subduction. Jurassic granites are also linked to Pacific subduction. Two Triassic samples could be affiliated to similar aged rocks in the Chanthaburi Terrane, or linked to the Loei Fold Belt and related to closure to the Sa Kaeo back arc. We cannot exclude that they are related to Pacific Plate. Correlation of Permian volcanics to paleo-Tethys subduction and the Sukhothai-Chanthaburi arc is not clear as the Cambodian volcanics are older than Chanthaburi rocks, and there are stratigraphic contrasts between S Cambodia and Chanthaburi. Furthermore, such a correlation requires extension of the Sa Kaeo suture into S Cambodia and SW Vietnam at a high angle to regional structures. We propose that the Permian volcanics are also related to Paleo-Pacific subduction as shown in regional reconstructions of the region.

展示了越南西南和柬埔寨南部火成岩的锆石年龄和地球化学。出现四个主要年龄组：白垩纪（107-75 Ma）、早侏罗纪（195 Ma）、晚三叠纪（230-222 Ma）和二叠纪（294-265 Ma）。白垩纪和侏罗纪样品是含角闪石的黑云母花岗闪长岩到黑云母花岗岩，主要产于贡布褶皱带以东。前白垩纪样品出现在贡布褶皱带内，主要是长英质火山岩。岩石主要是高钾钙碱性、弱过铝质流纹岩或花岗岩，具有类似的弧状微量元素模式。白垩纪花岗岩类似于大叻带花岗岩，形成于太平洋俯冲。两块白垩纪花岗岩具有类似埃达克岩的特征。最年轻的白垩纪花岗岩具有 A 型特征，可能代表俯冲停止后的碰撞后活动。侏罗纪花岗岩也与太平洋俯冲有关。两个三叠纪样本可能隶属于尖竹汶地层中类似的老化岩石，或与 Loei 褶皱带有关并与沙缴府后弧的闭合有关。我们不能排除它们与太平洋板块有关。二叠纪火山岩与古特提斯俯冲和素可泰-尖竹汶弧的相关性尚不清楚，因为柬埔寨火山岩比尖竹汶岩石更古老，柬埔寨南部和尖竹汶之间存在地层对比。此外，这种相关性需要将 Sa Kaeo 缝合线以与区域结构的高角度延伸到柬埔寨南部和越南西南部。