黑龙江跃进山杂岩中砾岩的碎屑锆石年代学及其大地构造意义

黑龙江省饶河县石场一带分布的跃进山杂岩为一套富含晚三叠世化石的海陆交互相沉积地层.砾岩样品中的LA-ICP-MS锆石U-Pb测年结果显示，样品中的碎屑锆石年龄谱具有4组年龄，分别为800 Ma以上、500 Ma、251~284 Ma和219~222 Ma.前三者与佳木斯地块中的热事件年龄完全一致，表明其沉积物源主要来自佳木斯地块；后者为砾岩最小年龄组，大致可将这组最小年龄视为这套砾岩的沉积时代下限，与西侧松辽地块东缘的张广才岭地区广泛分布的210~228 Ma的晚三叠世早期花岗岩基本一致，说明具有最小年龄组的碎屑锆石可能来自松辽地块东部.碎屑锆石年龄及其源区特征表明，在晚三叠世之前，跃进山增生杂岩已经就位在佳木斯地块东缘，并成为佳木斯地块东部大陆边缘的一部分.

DETRITAL ZIRCON CHRONOLOGY OF CONGLOMERATE IN YUEJINSHAN COMPLEX,HEILONGJIANG PROVINCE: Geotectonic Implications

The Yuejinshan Complex developed in Shichang area of Raohe County, Heilongjiang Province, is a set of marine-terrigenous sedimentary strata with rich Late Triassic fossils. The LA-ICP-MS zircon U-Pb dating results of conglomerate samples yield four groups of age, namely, above 800 Ma, 500 Ma, 251-284 Ma and 219-222 Ma respectively. The former three are completely in accordance with the ages of thermal events in Jiamusi massif, reflecting the sediment source mainly from Jiamusi massif. The latter, the youngest age group, can be roughly regarded as the latest sedimentary age of conglomerate. It is basically consistent with the early Late Triassic granite (210-228 Ma) widely distributed in Zhangguangcailing area of the east margin of Songliao massif, which indicates that the youngest detrital zircons are probably from the eastern Songliao massif. The characteristics of detrital zircon ages and source area reveal that the Yuejinshan accretionary complex has been located on and become a part of the east continental margin of Jiamusi massif before Late Triassic.