现代地质
現代地質
현대지질
GEOSCIENCE-JOURNAL OF GRADUATE SCHOOL CHINA UNIVERSITY OF GEOSCIENCES
2013年
6期
1340-1347
,共8页
豫西%早二叠世%碳酸盐台地%稀土元素%演化
豫西%早二疊世%碳痠鹽檯地%稀土元素%縯化
예서%조이첩세%탄산염태지%희토원소%연화
western Henan%Early Permian%carbonate platform%rare earth element%evolution
焦作-禹州地区下二叠统太原组沉积相可划分为5类:开阔台地相、局限台地相、障壁岛相、泻湖-沼泽相和潮坪相,海相碳酸盐岩地层中风暴沉积事件普遍发育。开阔台地主要发育生物碎屑灰岩,生物碎屑含量高且较为破碎,以 LREE 明显富集,∑REE、(LREE /HREE)N值与 Fe 含量正相关为特点,反映古水体开阔、动荡且富含生物碎屑和胶体。局限台地主要沉积泥晶灰岩,古水体环境表现为受限、相对安静的特点。研究区太原组下部灰岩段的底部灰岩形成于海侵体系域(TST),生物碎屑含量、∑REE 相对较高且轻重稀土无显著分异,Sr/Ba 比值小而 Ba 丰度高;顶部灰岩形成于高水位体系域(HST),显示台地水体逐渐受到限制,陆源控制作用减弱,演化为更加安静低能环境。不同体系域中局限台地灰岩的对比分析,可为恢复南华北二叠纪陆表海盆地古地理特征及演化提供重要资料。
焦作-禹州地區下二疊統太原組沉積相可劃分為5類:開闊檯地相、跼限檯地相、障壁島相、瀉湖-沼澤相和潮坪相,海相碳痠鹽巖地層中風暴沉積事件普遍髮育。開闊檯地主要髮育生物碎屑灰巖,生物碎屑含量高且較為破碎,以 LREE 明顯富集,∑REE、(LREE /HREE)N值與 Fe 含量正相關為特點,反映古水體開闊、動盪且富含生物碎屑和膠體。跼限檯地主要沉積泥晶灰巖,古水體環境錶現為受限、相對安靜的特點。研究區太原組下部灰巖段的底部灰巖形成于海侵體繫域(TST),生物碎屑含量、∑REE 相對較高且輕重稀土無顯著分異,Sr/Ba 比值小而 Ba 豐度高;頂部灰巖形成于高水位體繫域(HST),顯示檯地水體逐漸受到限製,陸源控製作用減弱,縯化為更加安靜低能環境。不同體繫域中跼限檯地灰巖的對比分析,可為恢複南華北二疊紀陸錶海盆地古地理特徵及縯化提供重要資料。
초작-우주지구하이첩통태원조침적상가화분위5류:개활태지상、국한태지상、장벽도상、사호-소택상화조평상,해상탄산염암지층중풍폭침적사건보편발육。개활태지주요발육생물쇄설회암,생물쇄설함량고차교위파쇄,이 LREE 명현부집,∑REE、(LREE /HREE)N치여 Fe 함량정상관위특점,반영고수체개활、동탕차부함생물쇄설화효체。국한태지주요침적니정회암,고수체배경표현위수한、상대안정적특점。연구구태원조하부회암단적저부회암형성우해침체계역(TST),생물쇄설함량、∑REE 상대교고차경중희토무현저분이,Sr/Ba 비치소이 Ba 봉도고;정부회암형성우고수위체계역(HST),현시태지수체축점수도한제,륙원공제작용감약,연화위경가안정저능배경。불동체계역중국한태지회암적대비분석,가위회복남화북이첩기륙표해분지고지리특정급연화제공중요자료。
This paper presents the study of the sedimentary facies of Taiyuan Formation in typical sections from Jiaozuo area to Yuzhou area,mainly focusing on the platform sedimentary characteristics and evolution of epi-continental sea.Sedimentary facies of Taiyuan Formation,which is mainly featured by limestones along with in-terlayered siltstones,mud shales and coal seams,can be divided into five facies including open carbonate plat-form,limited carbonate platform,barrier island,lagoon-swamp and tidal-flat facies.The storm depositional events widely developed in the carbonate platform,which can be divided into several sedimentary cycles.Open carbonate platform (mainly in Yuzhou area)mainly contain amount of bioclastic,featured by substantial broken fossils,high content of trace elements and rare earth elements,much higher content of LREE than that of HREE,the respectively positive correlations between the value of ∑REE and the content of Fe as well as between that of LREE /HREE and Fe.Compared with open carbonate platform,restricted carbonate platform (mainly in Jiaozuo area)is featured by the widespread micrite,which infer that the ancient ocean in the restricted carbonate platform contained less fossils and colloids,and became much more restricted and quieter than that of open carbonate platform.The bottom limestones of the Lower Limestone Section of Taiyuan Forma-tion,which is formed in transgressive systems tract(TST)during the early phase of first transgression,are fea-tured by high content of biodetritus,Sc,Ba and ∑REE,low value of Sr/Ba,low differentiation between LREE and HREE.The top limestones of the Lower Limestone Section formed in highstand systems tract (HST), which reflected the sedimentary environment of the limited carbonate platform in the research area evolving from the previous turbulent water into confined and quite surroundings with biodetritus and collides diminishing and evaporation strengthening.It aims to put implications on the research of the characteristics and evolution by comparing with the sedimentary characteristics of Taiyuan Formation limestones in different stage of the system tracts in restricted carbonate platform.