【摘要】 发育于秦岭板块结合部位的黑河砾岩是由水下碎屑流，颗粒流和砾质高密度浊流形成的。它们与周围相关岩相一起构成了二个明显的相组合，代有了二个独立的裙状沉积体。组合Ⅰ中的砾岩是由火山泥流泻入浅水碳酸盐台地之上沉积而成，而组合Ⅱ中的砾岩则与中一细粒浊积岩一起表现为深水远端沉积。砾岩的形成和发展与古生代秦岭板块的俯冲及相邻火山岛弧的演化密切相关，是当时弧前盆地沉积体的一个组成部分。更多还原

【Abstract】 Abstract The Shangdan fault zone is the most important tectonic boundary within the Qinling orogen during the Phanerozic. A large volume of sedimentary rocks, which formed in the suobduction process of north and south Qinling plates, is preserved in the zone. Conglomerate is the facies which is believed to be closely related to orogenesis. Different sorts of conglomerate are produced in distinct tectonic settings. Heihe conglomerate within the Shangdan zone was considered to be Mollasse of hasal conglomerate in previous studies, and accordingly served as a crucial piece of evidence suppotting the inferrence that the Qinlin orogenic belt was built during the Caledonian Period. However, this study shows that Heihe conglomerates is actually fore-arc deposits in the process of plate subouction and can not be interpreted as product resulting from plate collison.Heihe conglomerate can be divided into six different factes and two distinct f&cies associations. Most fscies were depotted from debris flows and density-modified grainflows, and conglomeratic beds show clear evidence of laminar flow. The others represent gravelly high-density turbidites.Grading is well developed in conglomerate beds, including inverse, inverse-to-normal, and normal, but structureless or massive beds are also common. Some of gravity flows probsbly underwent flow transformation, for instance, certain debris flows might originate from turbidity currents. It is proved that all the conglomerate formed in a subaqueous environments. This conclusion is mainly based upon the analyses of internal sedimentary structures of conglomerates and their close association with turbidites. Two distinct facies associations actually build two independent conglomerate lenticular bodies in space. AssociationⅠconsists predominantly of clast-supported conglomerate with abundant are derived materials, and pyroclastic rocks are clearly coexisting It is believed that AssociationⅠwas depotted from lahar which flowed from volcanic island to a foreare basin. Matrix-supported conglomerate is characteristic of Association Ⅱand obviously interlayered with fine to medium grained turbidites. Especially, the two associations occurred separately, indicating that they were typically two independent subaqueous apron deposit. Different fsctors controlled the development of the two distinct aprons. Volcanic eruptions were the main cause of initiation of lahar which produced AssociationⅠ, while faulting triggered the occurrence of submarine gravity flows which brought about formation of Assocition Ⅱ.A direct relationship exists between sedimentation of conglomerate and co-existing lithofacies and evolution of Danfeng ophiolites. Sedimentary sequence conformably overlies volcanic rocks of southern arc flank of the inferred arc and is approximately concurrent with arc development. Conglomerate, together with other lithofacies, was evidently fore-are basin fills and resulted from coeval subouction tectonism. The two associations occurred in different parts of basin and therefore possessed distinct factes sequences. Heihe area was marked by occurrence of small-scale apron dealts instead of well-developed large-scale submarine fans. reflecting an unstable tectonic sedimentary environment at that time.更多还原