Collaborative Research: Cenozoic Evolution of the Aleutian-Kamchatka Junction

这是一项与耶鲁大学和联合学院首席研究员的合作提案。这项提议得到了波罗的海国家、保加利亚、波兰、前苏联独立国家、国际项目的联合资助。堪察加地区包含了北太平洋盆地板块构造演化的详细、完整的记录，这对于解决阿留申火山弧的起源和白令海下的主要地质特征至关重要。堪察加半岛下面至少有两个奇异的岛弧，它们形成于白垩纪晚期和第三纪早期的低纬度地区，距今9000万至6000万年前（Ma），然后向北移动，与俄罗斯东北大陆边缘碰撞。首先发生碰撞的是奥利托尔斯基岛弧，它沿瓦季纳逆冲带覆盖了俄罗斯的边缘，大约45毫安。堪察加角弧线接着相撞。这次碰撞没有得到很好的解决，但可能开始于中新世晚期（15 Ma），目前似乎在阿留申-堪察加交界处活跃。这次碰撞事件很复杂，因为碰撞弧线的碎片沿着堪察加半岛东侧的突出海角被隔离，可能还包括科曼多尔斯基群岛和阿留申群岛西部。目前与这些奇异弧线接壤的构造带包含了碰撞时间和运动学的宝贵记录。主要研究人员已经研究了瓦提纳部分逆冲的年龄和运动学，并将继续研究横跨堪察加地峡到堪察加角的南部横断面的两个碰撞区，以确定Olyutorsky弧和堪察加角弧的碰撞历史的年龄。他们选择了三个目标区域：1)在堪察加地峡的列斯诺夫斯克高地的瓦季纳断裂带的南部延续性；2)卡拉金斯基岛东侧暴露出Vetiovsky杂岩，这是一个形成于Olyutorsky弧外侧的年代不确定的俯冲杂岩；3)在堪察加角以西，维捷洛夫斯基俯冲复合体被夹在奥利托尔斯基弧和堪察加角弧之间。他们将确定从卡拉金斯基岛开始的维特洛夫斯基复合体的延续时间，以确定始新世到中新世的秋舍夫盆地是如何以及何时开始与该地区的旧构造单元重叠的。这一信息应该提供了堪察加角弧首次到达堪察加边缘的记录。他们将使用来自大陆砂岩的碎屑锆石的裂变径迹测年法。对单个锆石定年将使他们能够从统计上分离出最年轻的颗粒年龄。测年方法是精确的（相对标准误差为3.5%），并将提供构造上重要的岩石组的年龄信息。该方法还将用于确定纵横切和封闭列诺夫斯克高地瓦季纳逆冲构造的火山岩和岩体的年代。一些年龄将由更昂贵的高精度铀/铅锆石年龄补充。

AbstractOPP-9911925BrandonOPP-9911910GarverThis is a collaborative proposal with Principal Investigators from Yale University and Union College. This proposal is receiving joint funding from the Baltic States, Bulgaria, Poland, Independent States of the Former Soviet Union, International Programs. The Kamchatka region contains a detailed, well-exposed record of the plate tectonic evolution of the north Pacific basin, essential for resolving the origin of the Aleutian volcanic arc and major geologic features beneath the Bering Sea. The Kamchatka is underlain by at least two exotic island arcs, which formed at low latitudes during the late Cretaceous and early Tertiary, 90-60 million years ago (Ma), and then moved north, colliding with the northeast Russian continental margin. The first to collide was the Olyutorsky island arc which overrode the Russian margin along the Vatyna thrust about 45 Ma. The Cape Kamchatka arc collided next. The collision is poorly resolved, but may have started in late Miocene (1 5 Ma) and appears to be presently active at the Aleutian-Kamchatka junction. This collision event is complicated because the pieces of the collided arc are isolated along the prominent capes on the east side of the Kamchatka Peninsula and may also include the Komandorsky Islands and western Aleutian Islands.The tectonic zones that presently border these exotic arcs contain a valuable record of the timing and kinematics of the collisions. The Principal Investigators have studied the age and kinematics of part of the Vatyna thrust and will continue to study both collision zones in the southern transect across the Kamchatka Isthmus to Cape Kamchatka to establish the ages for the collisional history of the Olyutorsky and Cape Kamchatka arcs. They have selected three target areas: 1) southern continuation of the Vatyna thrust in the Lesnovsk Highland of the Kamchatka Isthmus; 2) the east side of Karaginsky Island which exposes the Vetiovsky complex, a poorly dated subduction complex that formed outboard of the Olyutorsky arc; and 3) west of Cape Kamchatka where the Vetiovsky subduction complex has been pinched between the Olyutorsky arc and the more outboard Cape Kamchatka arc. They will date the continuation of the Vetlovsky complex from Karaginsky Island to determine how and when the Eocene to Miocene Tyushev basin began to overlap the older tectonic units in this area. This information should provide a record of the first arrival of the Cape Kamchatka arc at the Kamchatka margin.They will use fission-track dating of detrital zircons from continental-derived sandstones. Dating of individual zircons will allow them to statistically isolate the youngest fraction of grain ages. The dating method is precise (relative standard error - 3.5%) and will provide age information about a tectonically important group of rocks. The method will also be used to date volcanic rocks and plutons that crosscut and seal the Vatyna thrust in the Lesnovsk highlands. Some ages will be supplemented by more expensive high precision uranium/lead zircon ages.