Collaborative Research: Cenozoic Evolution of the Aleutian-Kamchatka Junction

这是一个与耶鲁大学和联合学院的主要研究人员合作的提案。 这项建议得到了波罗的海国家、保加利亚、波兰、前苏联独立国家、国际方案的联合资助。 堪察加半岛地区包含了北太平洋盆地板块构造演化的详细、暴露良好的记录，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。 堪察加半岛的下面至少有两个奇异的岛弧，它们形成于9000 - 6000万年前（Ma）的白垩纪晚期和第三纪早期的低纬度地区，然后向北移动，与俄罗斯东北部的大陆边缘碰撞。 第一次碰撞是奥柳托尔斯基岛弧，它沿着瓦蒂娜逆冲断层沿着覆盖俄罗斯边缘，约45 Ma。堪察加角弧随后相撞。 碰撞是解决不好，但可能已经开始在晚中新世（1 - 5马），目前似乎活跃在阿留申-堪察加交界处。 这一碰撞事件是复杂的，因为碰撞弧的碎片被隔离沿着堪察加半岛半岛东侧的突出海角，也可能包括科曼多尔斯基群岛和阿留申群岛西部。目前这些外来弧的边界的构造带包含了碰撞的时间和运动学的宝贵记录。 主要研究人员已经研究了Vatyna逆冲断层部分的年龄和运动学，并将继续研究横跨堪察加地峡到堪察加角的南部断面的两个碰撞区，以确定Olyutorsky弧和堪察加角弧碰撞历史的年龄。 他们选择了三个目标区域：1）堪察加地峡Lesnovsk高地的Vatyna逆冲断层的南部延续; 2）Karaginsky岛的东侧，暴露了Vetiovsky复合体，这是一个日期不确定的俯冲复合体，形成于Olyutorsky弧的外侧;和3）在堪察加角以西，Vetiovsky俯冲复合体被夹在Olyutorsky弧和更外侧的堪察加角弧之间。 他们将确定从卡拉金斯基岛延续的维特洛夫斯基复合体的日期，以确定始新世到中新世的秋舍夫盆地如何以及何时开始与该地区较老的构造单元重叠。 这些信息将提供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裂变径迹定年法。 对单个锆石的定年将使他们能够在统计上分离出颗粒年龄中最年轻的部分。测年方法是精确的（相对标准误差-3.5%），并将提供有关构造上重要的岩石群的年龄信息。该方法还将用于确定Lesnovsk高地横切和密封Vatyna逆冲断层的火山岩和岩体的年代。 一些年龄将补充更昂贵的高精度铀/铅锆石年龄。

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.