摘要
本文根据边界断裂的控相特征、区内代表深成构造活动的层状堆晶基性—超基性岩的产出、二叠纪—三叠纪海底拉斑玄武岩的喷溢活动特征、巨厚的浊积岩建造和混杂式建造的共生以及地球物理特征,认为松潘—甘孜地块内部存在炉霍海底裂谷。炉霍裂谷二叠纪—三叠纪经历了初始裂陷、沉积—拗陷、高度裂陷至萎缩消亡的4个阶段。裂谷封闭后,在逆冲挤压造山环境中,形成以Ⅰ型为主的中酸性侵入体,区域构造应力场经历了燕山早期近WSW—ENE向挤压,燕山晚期近NNW—SSE向挤压至喜马拉雅期近NE—SW向挤压的演化。
The Luhuo palaeorift lies in the Garze - Songpan massif. Its boundary faults, the Dingqu -Jiajinong - Quesuo fault and the Ximaliduo - Sertar fault, were reflected as faults cutting the lithosphere during the late Variscan and Indosinian periods. They dip NE and SW respectively, forming the graben -type sea basin. The stratified cumulus basic - ultrabasic intrusive bodies in the rift are the result of deep-seated tectonic intrusion. The Permian and Triassic volcanic rocks outcropping in the region are characteristic of seafloor (or mid - oceanic ridge) tholeiite as viewed from their occurrence, lithology and chemical composition. The Permian basalts and basic-ultrabasic rocks at the bottom of the Permian strata may be the constituents of ophiolite, which may be the primary oceanic crust formed by the spreading of the back - arc marginal sea. The chemical composition of basic-ultrabasic rocks associated with Triassic basalts reveals the tectonic evolution from continental rifting to oceanic rifting. The development of turbidite, volcanic rocks, olistostrome and deep -sea cherts with a considerable thickness is different from that of the adjacent region. The materials for deposition were mainly from the northeastern and southwestern directions, which supports the existence of the rift. The Luhuo belt is also the boundary between subregions of regional magnetic fields, in which linear magnetic anomalies are shown. It can be determined from the above that the Luhuo palaeorift is a Permian - Triassic seafloor rift developed on the Yangtze -type basement. It experienced the primary rifting stage (in the Late Permian) , depositional depression stage (in the Early to Late Triassic) , intense rifting stage (in the middle Late Triassic), and withering stage (in the late Late Triassic). After the closing of the rift, due to the interaction among th Indian plate, Pacific plate and Sino-Korean plate, the Songpan-Garze massif including the Luhuo rift was in a depression environment, in which Yan-shanian intermediate-acid intru
出处
《地质学报》
EI
CAS
CSCD
北大核心
2000年第3期247-253,共7页
Acta Geologica Sinica
基金
国家攀登预选项目(编号95-预-25)
中国科学院重大科研项目(编号KZ951-131-141)
