Greenstone bodies emplaced upon or into clastic sediments crop out ubiquitously in the Hidaka belt (early Paleogene accretionary and collisional complexes exposed in the central part of northern Hokkaido, NE Japan), but the timing and setting of their emplacement has remained poorly constrained. Here, we report new zircon U–Pb ages for the sedimentary complexes surrounding these greenstones. The Hidaka Supergroup in the northern Hidaka belt is divided into four zones from west to east: zones S, U, and R, which contain in situ greenstones; and zone Y, which does not. Detrital zircons in zones S, U, and R have early Eocene U–Pb ages (55–47 Ma) and these strata are intruded by early Eocene granites (46–45 Ma), indicating that they were deposited between 55 and 46 Ma. Therefore, in situ greenstones in the northern Hidaka belt can only be explained by the subduction of the Izanagi–Pacific Ridge during 55–47 Ma. In contrast, the deposition of zone Y (the Yubetsu Group, younging to the west) began by 73–71 Ma, indicating that the accretionary prism in front of the paleo‐Kuril arc formed at the same time as that in the Idonnappu zone and grew continuously until 48 Ma. The plutonic rocks that intruded the Hidaka belt are roughly divided into three stages: (1) early Eocene granites intruded the northern Hidaka belt at 46–45 Ma, during subduction of the Izanagi–Pacific Ridge; (2) the upper sequence of the Hidaka metamorphic zone was metamorphosed by magmatism at 40–37 Ma associated with the collision of the paleo‐Kuril arc and NE Asia; and (3) younger granites intruded the entire Hidaka belt at 20–17 Ma in association with asthenospheric upwelling caused by back‐arc expansion.

中文翻译：

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日高北部地带原位绿岩的埋置：伊萨纳吉-太平洋山脊俯冲与日高岩浆活动之间的构造关系

在日高地带（在日本东北部北海道中部暴露出的古近代增生和碰撞复合体）中，到处都是碎屑沉积物或碎屑沉积物中的绿岩体，随处可见。在这里，我们报告了这些绿岩周围沉积复合物的新锆石U–Pb年龄。日高北部地带的日高超群从西到东分为四个区域：S，U和R区，其中包含原位绿岩。和区域Y，但没有。S，U和R区的碎屑锆石具有早始新世U-Pb年龄（55-47 Ma），这些地层被早始新世花岗岩（46-45 Ma）侵入，表明它们沉积在55-46 Ma之间。因此，就地日高北部地带的绿岩只能由伊萨纳吉-太平洋海岭在55-47 Ma的俯冲来解释。相比之下，Y区（尤别津族，向西年轻）的沉积始于73-71 Ma，表明古-库里尔弧前的增生棱镜与Idonnappu区同时形成。持续生长直到48 Ma。侵入日高地带的深成岩大致分为三个阶段：（1）在伊萨纳吉-太平洋山脊俯冲期间，始新世早期花岗岩侵入日高地带的北部为46-45 Ma。（2）日高变质带的上层层序是在40-37 Ma的岩浆作用下变质的，与古库里尔弧和东北亚的碰撞有关。