CAJ | 학술논문

阿拉善地块的构造归属长期以来存在争议。我们对阿拉善地块东南部牛首山地区中—晚泥盆世砂岩的物源开展碎屑锆石U-Pb年代学与Hf同位素研究。碎屑锆石U-Pb年龄谱主要分布在5个区间：0.4—0.7 Ga,1.0—1.3 Ga,1.5—1.8 Ga,2.4—2.8 Ga和＞3.0 Ga,并获得一颗年龄为(4022±17) Ma的冥古宙锆石。2.4—2.7 Ga、＞3.0 Ga碎屑锆石和它们对应的εHf(t)值明显不同于华北板块同时代碎屑锆石,暗示着阿拉善地块与华北板块中—晚泥盆世并未相连。同时,我们还对地块东部的早石炭世、晚二叠世和早中三叠世地层开展了详细的古地磁研究,获得了相应的视极移曲线。我们结合碎屑锆石年代学和古地磁学研究,提出阿拉善地块前中生代与柴达木—塔里木地块具有亲缘性,而很可能与华北地块分离。印支运动使阿拉善地块相对于华北发生了32度的逆时针旋转,正是这一旋转运动使河西走廊—阿拉善地块最终与华北地块拼合形成了统一地块。
아랍선지괴적구조귀속장기이래존재쟁의。아문대아랍선지괴동남부우수산지구중—만니분세사암적물원개전쇄설고석U-Pb년대학여Hf동위소연구。쇄설고석U-Pb년령보주요분포재5개구간：0.4—0.7 Ga,1.0—1.3 Ga,1.5—1.8 Ga,2.4—2.8 Ga화＞3.0 Ga,병획득일과년령위(4022±17) Ma적명고주고석。2.4—2.7 Ga、＞3.0 Ga쇄설고석화타문대응적εHf(t)치명현불동우화북판괴동시대쇄설고석,암시착아랍선지괴여화북판괴중—만니분세병미상련。동시,아문환대지괴동부적조석탄세、만이첩세화조중삼첩세지층개전료상세적고지자연구,획득료상응적시겁이곡선。아문결합쇄설고석년대학화고지자학연구,제출아랍선지괴전중생대여시체목—탑리목지괴구유친연성,이흔가능여화북지괴분리。인지운동사아랍선지괴상대우화북발생료32도적역시침선전,정시저일선전운동사하서주랑—아랍선지괴최종여화북지괴병합형성료통일지괴。
Tectonic affinity of the Alxa Block has long been a topic of much controversy. In this study, samples of Middle–Late Devonian sedimentary rocks were systematically collected from the Niushou Mountain in southeastern Alxa Block. The detrital zircon U-Pb ages define five age populations: 0.4–0.7 Ga, 1.0–1.3 Ga, 1.5–1.8 Ga, 2.4–2.7 Ga and>3.0 Ga. Zircons with U-Pb age spectra of 2.4–2.7 Ga,>3.0 Ga and their correspondingεHf(t) values are significantly different from data obtained from the North China Block, which implies that the Alxa Block was not part of North China until the Middle–Late Devonian. In addition, paleomagnetic study of the Late Devonian to Middle Triassic strata in the Niushou Mountain and the eastern part of the Alxa Block was carried out and, as a result, the apparent polar wander paths (APWP) were established. These results indicate that the Alxa Block had a close affinity with the Qaidam–Tarim Block, but was separated from the North China Block prior to the Pre-Mesozoic. The Alxa Block suffered from a counterclockwise rotation of 32° with respect to the North China Block during the Indosinian orogeny and finally amalgamated with the North China Block into a unified block before the Early Cretaceous.