东北中生代增生杂岩及对古太平洋向欧亚大陆俯冲历史的制约

吉林-黑龙江东部地区的中生代增生杂岩,主要由吉林-黑龙江高压变质带和那丹哈达增生杂岩(或那丹哈达地体)组成。它们将为古亚洲洋与环太平洋构造域的转换作用,大洋板块地层(OPS)层序重建,特别是古太平洋板块向欧亚大陆的俯冲历史提供重要的科学依据。吉林-黑龙江高压带分布在佳木斯-兴凯与松辽地块之间的具有高压变质带性质的缝合带,新的地质年代学研究表明其形成时代为210～180Ma,表明晚三叠-早侏罗世为南北向古亚洲洋关闭和西向俯冲增生开始的关键时期。那丹哈达增生杂岩则发育在佳木斯-兴凯地块东侧,并具体分为西部的跃进山杂岩和东部的饶河杂岩。新近发表的数据显示,跃进山杂岩就位时代为210～180Ma,这与佳木斯-兴凯地块西缘的吉黑高压带形成时代相似。而饶河杂岩就位时代为晚侏罗-早白垩世,最晚期就位的时代为早白垩世(137～130Ma)。因此,吉黑东部地区的中生代增生杂岩为古太平洋向欧亚大陆中生代的俯冲过程提供了关键的信息。

The Mesozoic accretionary complex in NE China and its tectonic implications for the subduction of the Paleo-Pacific plate beneath the Eurasia

The Mesozoic accretionary complex in eastern part of the Jilin-Heilongjiang provinces of China, which mainly consists of the Jilin-Heilongjiang HP belt and the Nadanhada accretionary complex (or Nadanhada terrane), are the key evidence to understand the transformation from closure of Central Asian Ocean and beginning of the subduction of the Pacific plate beneath the Eurasia, reconstruction of the oceanic plate stratigraphy (OPS), especially, the history of the Paleo-Pacific subduction. The Jilin-Heilongjiang HP belt is the typical high-pressure metamorphism suture zone between the Jiamusi-Khanka and Songliao blocks and consists of the Heilongjiang blueschists belt and the Zhangguangcai accretionary complex. The Heilongjiang blueschist belt was overthrust onto the Jiamusi Block along the Mudanjiang fault in the western part of the Jiamusi massif and the blueschist facies metamorphism on these rocks has been recognized by the occurrence of diagnostic mineral glaucophane. The glaucophane in the blueschist often occurs in two forms:one is in fibrous structure, and the other occurs at the boundary between albite crystals, defining a strong lineation. The glaucophane was identified as crossite by electron microscopy, indicating epidote-blueschist facies metamorphic conditions. The Zhangguangcai complex consisting of the majority of the Jilin-Heilongjiang HP belt is located to the west of the Heilongjiang complex. It is mainly composed of greenschist, marble, two-mica schist, quartz schist, quartzite and metavolcanic rocks; all these units occur as tectonic blocks in the Mesozoic granite. New geochronological data indicate that the collision between the Jiamusi-Khanka and Songliao blocks along the Jilin-Heilongjiang HP belt occurred between 210Ma and 180Ma, suggesting that the Jilin-Heilongjiang HP belt is an important unit for characterizing the geodynamic switch from the north-south closure of the Central Asian Orogenic Belt to the onset of westward-directed accretion related to subduction of the Pacific plate during the Latest Triassic to Early Jurassic. The Nadanhada accretionary complex lies to the east of the Jiamusi-Khanka Block, and is composed of the Yuejinshan and Raohe complexes. The Yuejinshan complex is located adjacent to the Jiamusi-Khanka block and consists of metamorphosed marine clastic rocks, interpreted as continental slope sediments, in association with ophiolitic components consisting of metabasalt with N-MORB affinity, gabbro, and ultramafic rocks that include dunite, wehrlite and clinopyroxenite. The Raohe complex, the major component of the Nadanhada terrane, is mostly located to the east of the Yuejinshan complex. The Raohe complex is mainly composed of limestone, chert, clastic sedimentary rocks, basaltic pillow lava with OIB affinity and mafic-ultramafic rocks, all these units occur as blocks in a weakly deformed clastic sedimentary matrix and are thus olistoliths in an accretionary complex. New data indicate that the Yuejinshan complex was probably formed between 210 Ma and 180Ma, similar ages to the Jilin-Heilongjiang HP belt along the western margin of the Jiamusi-Khanka Block. The Raohe complex was formed later in the Late Jurassic to Early-Cretaceous (170~137Ma), likely more related to the Paleo-Pacific plate subduction-accretion. The final accretion in the area took place in the Early Cretaceous (137~130Ma). Therefore, the Mesozoic accretionary complex, in eastern part of the Jilin-Heilongjiang provinces of NE China, which provide key information to discovery the process of the Paleo-Pacific plate beneath the Eurasia during the Mesozoic.