西昆仑及邻区区域构造演化的碎屑锆石裂变径迹年龄记录

通过对西昆仑北部山前的碎屑锆石裂变径迹年代学分析,将年龄划分为8个峰值区间:P1—4.7Ma以来;P2—13～9Ma;P3—24～18Ma;P4—47～33Ma;P5—79～57Ma;P6—131～103Ma;P7—185～180Ma;P8—267～235Ma,各峰值分布受阶段性抬升剥露和热事件共同影响。P8与P5主要受热事件控制,P6、P4、P3、P2、P1主要和抬升剥露有关,P7主控因素不明显。裂变径迹年龄峰值与西昆仑及邻区发生的一系列重大构造事件的时限吻合,并伴随强烈的区域性断裂活动,指示裂变径迹年龄峰值记录了西昆仑及邻区构造演化的重大事件;其中,晚白垩世以来喜马拉雅东、西构造结抬升具有相似性,反映了青藏高原自印度板块与欧亚大陆碰撞以来经历了相似的阶段性抬升。柯克亚连续沉积剖面显示西昆仑及邻区4.7Ma以来开始最后一次大规模抬升,并指示上新世以来西昆仑及邻区的径迹年龄储备表现出由多样性向一致性、由无规律向年轻化的发展趋势,暗示4.7Ma以来的抬升具整体抬升性质;3.6Ma为抬升的转折点,表现为抬升剥露速率加快、基底开始大规模出露地表,西昆仑山对南边的水流形成障碍。

The detrital zircon fission-track ages constraint to tectonic processes in west Kunlun and adjacent regions

Based on the detrital zircon fission-track age analysis on the northern foot of the western Kunlun Mountains,we plotted out 8 ranges of peak values,P1:since 4.7 Ma,P2:13-9 Ma,P3:24-18 Ma,P4:47-33 Ma,P5:79-57 Ma,P6:131-103 Ma,P7:185-180 Ma,P8:267-235 Ma;all the peaks resulted from the periodical uplift and thermal events.The main control factor of P8 and P5 are thermal events;and that of P6,P4,P3,P2,P1 are uplift and exhumation;the cause of P7 is unsure.The consistency of a series of important tectonic events and associated intensive regional fault activities reveal that the fission-track peaks recorded important tectonic events around the western Kunlun Mountains and adjacent regions;among them,the uplifts of west and east tectonic syntaxes of the Tibetan plateau since the late Cretaceous are similar,which reflects that the Tibetan plateau underwent similar periodical uplifts since the collision between Indian and Eurasian plates.The continuous depositional succession of Kekeya reveals that 4.7 Ma was the beginning of the last large scale uplift,and it shows that the fission-track age trend evolved since the Pliocene from diversity to simplicity and from irregularity to becoming younger in these regions.It implies that the uplifts behaved as an integration and 3.6 Ma was the turning point of uplift process,since then the uplift and exhumation rate had been accelerated,most of the basement rocks began to outcrop onto the surface and the western Kunlun Mountains became the obstacle to the currents from the south.