Collaborative Research: Cenozoic Evolution of the Aleutian-Kamchatka Junction

AbstractOPP-9911925BrandonOPP-9911910GarverThis是与耶鲁大学和联合学院的首席研究人员合作的提案。这项提案得到了波罗的海国家、保加利亚、波兰、前苏联独立国家和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、曝光的记录，这对于确定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9000万-6000万年前的白垩纪晚期和第三纪早期的低纬地区，然后向北移动，与俄罗斯东北部大陆边缘相撞。第一个相撞的是Olyutorsky岛弧，它沿着Vatyna逆冲约45 Ma越过俄罗斯边缘。接下来，堪察加角弧发生了碰撞。碰撞没有得到很好的解决，但可能开始于中新世晚期(15 Ma)，目前似乎活跃在阿留申-堪察加交界处。这次碰撞事件是复杂的，因为碰撞的弧段沿着堪察加半岛东侧的突出海角孤立，还可能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的时间和运动学的宝贵记录。首席调查人员研究了部分瓦蒂纳逆冲推覆的年龄和运动学，并将继续研究横跨堪察加地峡至堪察加角的南部样带的两个碰撞带，以确定Olyutorsky弧和堪察加角弧的碰撞历史。他们选择了三个目标区：1)堪察加地峡莱斯诺夫斯克高地瓦蒂纳冲断的南端；2)卡拉金斯岛东侧，暴露出奥柳托尔斯基弧外形成的一个陈旧的俯冲杂岩--维蒂奥夫斯基杂岩；以及3)堪察加角以西，维蒂奥夫斯基俯冲杂岩被夹在奥柳托斯基弧和更外侧的堪察加角弧之间。他们将确定卡拉金斯岛Vetlovsky杂岩的延续时间，以确定始新世至中新世Tyushev盆地如何以及何时开始与该地区较老的构造单元重叠。这些信息应该提供堪察加角弧第一次到达堪察加边缘的记录。他们将使用裂变径迹测定大陆砂岩中的碎屑锆石。对单个锆石的测年将使他们能够从统计上分离出最年轻的颗粒年龄部分。测年方法是精确的(相对标准误差为-3.5%)，将提供一组具有重要构造意义的岩石的年龄信息。这种方法还将用于测定横切和封闭莱斯诺夫斯克高地瓦蒂纳逆冲推覆的火山岩和深成岩的年代。一些年龄将被更昂贵的高精度铀/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.