新疆北部泥盆纪火山沉积岩系作用相类型、序列及其与板块构造的关系

PROCESS-FACIES TYPES AND SEQUENCES OF DEVONIAN VOLCANIC-SEDIMENTARY SUCCESSIONS IN NORTHERN XINJIANG AND THEIR RELATION TO PLATE TECTONICS

新疆北部泥盆纪火山沉积岩系的作用相类型主要包括:爆发相、溢流相,火山碎屑、钙屑、陆屑风暴岩相,火山喷发海啸岩相,粗粒、中粒、细粒火山碎屑浊积岩相,同沉积、软变形震积岩相和砂质、粉砂泥质等积岩相。文章阐述了它们的特征和识别标志,并以东准噶尔纸房剖面和西准噶尔沙尔布尔提山剖面为例,讨论了作用相和环境相的时空结构及与板块构造的关系。并认为以作用相为主体的相分析是槽区、造山带和活动大陆边缘相分析的特色所在。

The process-facies types of Devonian volcano-sedimentary successions in northern Xinjiang include explosive and effusive facies, pyroclastic and calcareous and terrigenous tempestite facies, and coarse-, medium-and fine-grained pyroclastic turbidite facies, volcanic eruption tsunamite facies, syndepositional and soft- deformed seismite facies, sandy and silt-muddy contourite facies. Their characteristics and diagnostic indicators have been presented. Sedimentary dynamic and facies dynamic studies indicate that from the Early Devonian to Late Devonian, the environment-facies sequence of the Zhifang section, east Junggar, is represented by the littoral→littoral and neritic→bathyal and abyssal transgressive one, rather than the facies sequence of marine facies (D_1)→transition facies (D_2)→ continental facies (D_3) as suggested by predecessors. The Process-facies sequence of the Zhifang section is dominated by the event-facies cycles. The proportion of the endogenic event-facies in the process-facies increases from 28.6%(D_1) to 46.5% (D_2) to 55.0% (D_3). The above features show that the interaction of the east Junggar slab and the south continental margin of the Siberian plate strengthened gradually from Early Devonian to Late Devonian. Extension might take place in the early Early Devonian. Convergence might be dominant from the late Early Devonian to Late Devonian. The Early Devonian to Late Devonian environment-facies sequence of the Mount Sarburti section, west Junggar, is bathyal, neritic and littoral facies (D_1)→continental facies(D_2-D_3~1)→littoral and neritic facies (D_3~2). The process-facies sequence of the Mount Surburti section shows complex volcano-sedimentary cycles. The proportion of the endogenic event-facies in the process-facies increases from 27.8% (D_1) to 50.1% (D_2) to 22.4%(D_3), which indicates that the interaction of the west Junggar slab and the south continental margin of the Siberian plate underwent the evolution from convergence to extension during the Devonian.