ABSTRACT

Transform margins represent lithospheric plate boundaries with horizontal sliding of the oceanic plate, which in time and space replaced the subduction-related convergent margins. This happened due to the following: ridge-crest–trench intersection or ridge death along a continental margin (recent California and Baja California, Queen Charlotte–Northern Cordilleran, west of the Antarctic Peninsula, and probably Late Miocene–Pleistocene southernmost South America); change in the direction of oceanic plate movement (western Aleutian–Komandorsk and southernmost tip of the Andes); and island arc-continent collision (New Guinea Island). Post-subduction magmatism is related to a slab window that resulted from the spreading ridge collision (subduction) with a continental margin or slab tear formation after subduction cessation. Igneous magmatic series formed above the slab window or slab tear are similar in composition and show diversity of tholeiitic (sub-alkaline), alkaline, or even calc-alkaline and peraluminous rocks. The comprehensive geochemical dataset for igneous rocks (more than 2400 analyses) from the recent model geodynamic settings allowed us to build discriminant diagrams for the petrogenic oxides TiO₂ × 10–Fe₂O₃^Tot–MgO and trace elements Nb*5–Ba/La–Yb*10, which show distinctive rock features present on both convergent and Pacific-type transform margins. The author’s diagrams are capable of distinguishing volcanic and plutonic rocks formed above the subduction zones at an island arc and continental margin (related to convergent margins), from those formed in the strike-slip tectonic setting of transform margins along continents or island arcs.

抽象的

转换边距代表岩石圈板块边界，洋洋板块水平滑动，这在时间和空间上取代了与俯冲有关的会聚边缘。之所以发生这种情况，是由于以下原因：大陆边缘的山脊-顶峰-海沟相交或山脊死亡（最近的加利福尼亚州和下加利福尼亚州，南夏半岛西部的夏洛特皇后区-北山脉山脉，以及南美洲最南端的中新世-更新世）；海洋板块运动方向的变化（西阿留申－科曼多尔斯克和安第斯山脉的最南端）；与岛弧-大陆碰撞（新几内亚岛）。俯冲后岩浆作用与板块窗口有关，该板块窗口是由俯冲停止后大陆边缘或板块撕裂形成而引起的扩散脊碰撞（俯冲）引起的。在板状窗口或板状撕裂上方形成的火成岩浆系列成分相似，并显示出生烃性（次碱性），碱性甚至钙碱性和高铝质岩石的多样性。来自最新模型地球动力学设置的火成岩综合地球化学数据集（进行了2400多次分析）使我们能够建立成因氧化物TiO的判别图₂  ×10–Fe ₂ O ₃ ^Tot –MgO和痕量元素Nb * 5–Ba / La–Yb * 10，它们在会聚和太平洋类型转换边缘都表现出独特的岩石特征。作者的图能够区分在岛弧和大陆边缘俯冲带上方俯冲带上方形成的火山岩和深成岩（与收敛边缘相关），与沿大陆或岛弧的转换边缘走滑构造环境中形成的火山岩和深部岩石区分开来。