陆相碎屑岩旋回沉积记录中的物质响应及聚集规律——以济阳坳陷王家岗地区古近系孔店组为例

Material responses and accumulation patterns in cyclic sediment records of continental clastic rocks: taking the Paleogene Kongdian Formation of Wangjiagang area in Jiyang Depression as an example

旋回沉积记录中包含着丰富的地质信息。以济阳坳陷王家岗地区古近系孔店组为研究对象,开展了陆相碎屑岩旋回沉积中物质响应特征研究。结果表明,王家岗地区湖平面逐渐收缩的陆源碎屑沉积旋回包括颜色、岩性和粒度旋回,旋回沉积机理主要为间歇性盐湖的振荡作用。矿物旋回从灰色到红色地层,纵向上石英含量逐渐增加,钾长石含量逐渐增加,斜长石含量逐渐减少,方解石含量有所减少,硬石膏含量逐渐增加,矿物变化旋回与颜色旋回的变化具有较好的耦合关系。旋回变化与元素富集也具有一定的耦合关系,纵向上常量元素中Al,Ca,Fe,Mg含量有增加的趋势,微量元素中Sr,Ba,Ga,Co 4种元素含量有增加的趋势。旋回变化与元素含量比值也有较好的耦合关系,特别是Fe/Mn和V/Ni比值,呈现出多级次旋回变化的特征。研究证实了王家岗地区陆相碎屑岩旋回变化与矿物和元素含量具有较好的耦合关系,它们直接控制了矿物和元素的富集规律。后期成岩流体改造通过物质交换,影响旋回变化的物质响应和耦合规律。

Cyclic sediment records contain rich geological information.Taking the Paleogene Kongdian Formation in Wangjiagang area in Jiyang Depression as an example,this paper studied the characteristics of material response in the cyclic sediment records of continental clastic rocks.Three kinds of cycles including color,lithology and grain size were identified in the continental clastic deposits accumulated during the gradual shrinking of lake level in Wangjiagang area and the genetic mechanism of these cycles is intermittent fluctuation of the Salt Lake level.Vertically from gray to red strata,the mineral cycle features in progressively increasing contents of quartz and potassium feldspar,decreasing contents of plagioclasite and calcite,and increasing content of anhydrite.The mineral cycles and color cycles have a good coupling relationship.The cycles also have a certain coupling relationship with element enrichment.Vertically,the contents of major elements such as Al,Ca,Fe and Mg have an increasing trend;while the contents of trace element Sr,Ba,Ga and Co have an increasing trend.The cycles also have a certain coupling relationship with element ratios,especially Fe / Mn and V / Ni ratios,which show multiple cycles.It is confirmed that sedimentary cycles of the continental clastic rocks in Wangjiagang area have relatively significant coupling relationship with mineral contents and element enrichment,and the former directly control the latter.Late diagenetic fluid modification influences material response and coupling patterns of the cycles through material exchange.