华北中元古代浅海碳酸盐沉淀方式变化: 海水氧化还原条件波动的响应?*

2021-07-21 12:20吴孟亭孙龙飞史晓颖1汤冬杰
古地理学报 2021年4期
关键词:文石蓟县铁岭

吴孟亭 方 浩 孙龙飞 史晓颖1, 汤冬杰

1中国地质大学(北京)生物地质与环境地质国家重点实验室,北京 100083 2中国地质大学(北京)科学研究院,北京 100083 3中国地质大学(北京)地球科学与资源学院,北京 100083

1 概述

要全面了解元古宙中期大气和浅海氧化还原状态的演变规律,需开展跨盆地、长序列、多剖面、多指标的沉积地球化学综合研究。元古宙中期沉积地层厚度巨大并以碳酸盐岩为主,华北地台发育的长城系(1.8~1.6Ga)、蓟县系(1.6~1.4Ga)和青白口系(1.0~0.8Ga)总厚度可达9000m(Luetal.,2002),华南神农架群(1.46~1.06Ga)厚度可达12000m(Canfieldetal.,2018;旷红伟等,2018)。由于对这种巨厚的沉积序列进行连续系统的地球化学分析难度很大,因此,有必要开发更直观的、野外可识别的海水氧化还原条件指标。前人的研究成果表明,沉积岩的矿物学特征或可能直观地反映海水氧化还原条件,例如华北串岭沟组(1.65~1.64Ga)由赤铁矿构成的鲕铁岩和叠层石铁岩(Linetal.,2019)、下马岭组(1.40~1.35Ga)二段下部以鲕绿泥石(Tangetal.,2017a)和菱铁矿(Canfieldetal.,2018;Tangetal.,2018)为主的铁岩以及铁岭组(1.45~1.40Ga)二段叠层石微生物礁体内大量产出的海绿石,均可以反映浅海缺氧铁化的地球化学条件;反之,高于庄组(1.60~1.54Ga)二段产出的锰氧化物结核(Fangetal.,2020)和下马岭组二段中部发育的赤铁矿海相红层(Tangetal.,2020),则指示适度氧化的海洋化学条件。由此可见,矿物组合具有指示海水氧化还原条件的重要潜力。然而,上述矿物在地层中的产出并不连续,因此有必要开发更多在地层记录中相对连续的沉积学和矿物学标识,对直观反映海水氧化还原条件具有重要科学意义。

大量研究表明,随着大气和浅海氧化程度的逐步增强,前寒武纪浅海碳酸盐沉淀方式也发生了显著的改变: 在太古宙至古元古代往往发育大量海底沉淀(纤维状文石或方解石、微指状叠层石、鱼骨状方解石等),新元古代则常以水柱沉淀的碳酸盐灰泥占优势,而中元古代则表现出碳酸盐沉淀方式的过渡,存在2种沉淀方式的多次转换(Grotzinger,1989;Knoll and Swett,1990;Grotzinger and Kasting,1993;Sami and James,1994;Sumner and Grotzinger,1996)。碳酸盐沉淀方式的长期变化是随海水氧化还原条件的演变而发生的。有研究者提出,在缺氧、铁化的海洋化学条件下,Fe2+和Mn2+作为碳酸盐沉淀的强力抑制剂可能限制了方解石在水柱中成核—生长,但允许文石以海底沉淀形式产出(Sumner and Grotzinger,1996)。随着海洋氧化水体的扩张,Fe2+和Mn2+被氧化而从浅海中移除,使方解石可在水柱中成核—生长—沉淀。因此,碳酸盐岩序列中不同类型的碳酸盐沉淀,可能具有直观反映海水氧化还原条件的潜力,进而对全面了解元古宙中期大气和浅海复杂的氧化还原状态具有重要意义,尽管这仍然需要有针对性的地球化学数据验证。值得指出的是,碳酸盐沉淀方式多样,本研究所指的碳酸盐仅包括水柱沉淀的灰泥和海底沉淀的文石等原生沉淀,不包括机械破碎形成的内碎屑颗粒和早期成岩在孔隙水中形成的碳酸盐沉淀等其他类型的碳酸盐。

在将碳酸盐沉淀方式应用于前寒武纪浅海氧化还原条件分析之前,还有2种观点需要进一步验证。第1种观点是碳酸盐沉淀方式的长期变化可能只是由于碳酸盐饱和度长期下降所致(Grotzinger,1989,1990;Knoll and Swett,1990;Grotzinger and Kasting,1993;Grotzinger and James,2000),其与海水氧化还原条件并不直接相关。这种低饱和度条件不利于海底沉淀的快速形成,从而易被异地运移的沉积物所覆盖而终止生长。第2种观点则认为水柱中碳酸盐灰泥的沉淀是在大气低二氧化碳浓度背景下,如小于10 PAL(现代大气水平),通过蓝细菌的二氧化碳浓缩机制(CCM)所导致的(Riding,2006;Kah and Riding,2007)。由于这2种机制产生的碳酸盐在特征上相近,目前要准确判断究竟是哪种机制发挥了更大的作用,还需要进行大量细致的碳酸盐沉积学和配套的地球化学指标研究来验证。

为进一步拓展古海水化学条件分析的沉积学指标,从而高效、简便地实施碳酸盐岩地层氧化还原条件的直观分析,作者系统分析华北中元古代碳酸盐岩地层的沉积相特征,测试并收集了相关层位的氧化还原地球化学数据。试图通过对碳酸盐沉淀方式与海水氧化还原条件变化之间的相关性分析,为快速直观地分析前寒武纪碳酸盐沉积的氧化还原条件提供一种新的途径。

2 地质背景

2.1 地质概况

位于华北克拉通中部的燕辽盆地发育并保存了全球最好的元古宙中期沉积地层,总厚度超过9km(Luetal.,2002)。这套地层沉积于Columbia超大陆裂解(Zhaoetal.,2003,2011;Zhangetal., 2012)和Rodinia超大陆聚合(Lietal.,2008)期间,可划分为3系12组(陈晋镳等,1980),自下而上包括长城系(常州沟组、串岭沟组、团山子组、大红峪组)、蓟县系(高于庄组、杨庄组、雾迷山组、洪水庄组、铁岭组、下马岭组)和青白口系(长龙山组、景儿峪组)。长城系主要由石英砂岩和暗色页岩以及少量白云岩组成(Linetal.,2019);蓟县系以浅水碳酸盐岩为主,夹有较深水沉积的黑色页岩(Tangetal.,2016;Zhangetal.,2016);青白口系由下部长龙山组砂岩和上部景儿峪组碳酸盐岩组成(Tangetal.,2016)。由于蓟县系大部分地层连续(高林志等,2009;Suetal.,2010;Lietal.,2013;苏文博,2014)、变质程度较低、普遍低于葡萄石—绿纤石相(Lietal.,2003;Chuetal.,2007),因此笔者以蓟县高于庄组、野三坡雾迷山组、凌源雾迷山组和蓟县铁岭组(图 1)的若干层段为例,重点研究碳酸盐沉淀特征及与之配套的海洋化学条件。

A—研究区域交通位置简图;B—蓟县地区地质简图;C—平泉和凌源地区地质简图;D—野三坡地区地质简图。 B、C、D据全国1︰50万地质图(中国地质调查局,2013)图 1 华北中元古界碳酸盐岩剖面位置及地质背景Fig.1 Location of the Mesoproterozoic carbonate rock sections in North China and their geological background

2.2 沉积特征

A—蓟县高于庄组三段暗色钙质泥岩夹白云质灰岩;B—蓟县高于庄组三段臼齿构造;C—蓟县高于庄组三段似丘状交错层理(箭头示冲刷面);D—凌源雾迷山组四段交错层理;E—凌源雾迷山组四段微生物席纹层(风化面灰白色)与灰泥沉积互层(风化面深灰色);F—凌源雾迷山组四段扁平状砾石;G—蓟县铁岭组一段含锰白云岩夹浅绿色海绿石页岩;H—蓟县铁岭组二段底部竹叶状砾屑灰岩中的扁平状砾石; I—蓟县铁岭组二段柱状叠层石图 2 华北高于庄组、雾迷山组和铁岭组沉积特征Fig.2 Sedimentary features of the Gaoyuzhuang,Wumishan and Tieling Formations in North China

高于庄组与下伏大红峪组呈不整合接触,与上覆杨庄组呈整合接触。高于庄组自下而上分为4个亚组(或段): 官地亚组(一段)、桑树鞍亚组(二段)、张家峪亚组(三段)、环秀寺亚组(四段)(陈晋镳等,1980)。在蓟县剖面上,高于庄组厚约1500m,以中—厚层碳酸盐岩为主,夹少量薄层黑色页岩。一段底部为1层厚约3m的砂岩,其内波痕发育;主体以中厚层白云岩为主,富含丘状叠层石,常发生硅化,表现为浅潮下带沉积(乔秀夫等,2007)。二段底部发育约20m 厚的紫黑色薄层泥质白云岩夹富Mn页岩,缺乏波浪和潮汐构造,可见0.5~1mm直径的Mn结核,为正常浪基面以下的深潮下带沉积(Fangetal.,2020)。富Mn段上部为约40m厚的含Mn厚层白云岩,发育微生物席和波痕,为正常浪基面以上的浅潮下带至潮间带沉积(梅冥相,2007)。三段下部为薄—中层状微晶白云质灰岩,夹黑色页岩(图 2-A)和较多20~30cm大小的灰岩结核;上部为中—厚层微晶白云质灰岩,发育臼齿状构造(图 2-B;梅冥相,2005,2007)和微生物席纹层(Fangetal.,2020)。该段中与波浪和水流相关的沉积构造少见,但偶见丘状层理(图 2-C),代表风暴浪基面附近的深潮下带沉积(梅冥相,2005;Guoetal.,2015)。四段下部见有分米级纤维状文石海底扇,中—上部以块状微生物岩和厚层白云岩为主,主要形成于潮下带微生物礁岩环境(梅冥相,2005)。

凌源地区雾迷山组厚约2800m,与下伏杨庄组和上覆洪水庄组均为整合接触,为一套连续沉积的浅海碳酸盐岩,可识别出4个段,代表 4个沉积旋回(旷红伟等,2009;罗顺社等,2010)。一段由厚层微晶灰质白云岩和粉晶白云岩组成,含燧石条带和结核以及波纹状叠层石。二段为巨厚层微晶白云岩和纹层状粉晶白云岩,含少量燧石,叠层石以层状和波状为主。三段为厚层微晶—粉晶白云岩,含丰富的硅质条带,发育丘状和缓波状叠层石及凝块石。四段以中厚—薄层微晶灰岩为主,夹燧石条带和结核;微晶灰岩中发育臼齿构造(旷红伟等,2009),叠层石呈缓波状—柱状—层纹状过渡。雾迷山组发育多种浅水沉积标志(图 2-D),有丰富的叠层石、微生物席纹层(图 2-E)、内碎屑砾石(图 2-F)和大量燧石条带和结核,普遍缺乏陆源碎屑,代表环潮坪沉积(罗顺社等,2010;Kuangetal.,2012)。

铁岭组分为2段: 一段为富锰白云岩夹页岩(Guoetal.,2013;Tangetal.,2017b);二段以灰岩为主,发育大量叠层石。在蓟县铁岭子剖面,该组厚度超过300m(郭文琳等,2019)。铁岭组一段下部为中厚层含锰泥质白云岩夹薄层海绿石页岩(图 2-G),向上页岩夹层增多,并发育丘状交错层理(Tangetal.,2018);中部为中厚层富锰泥质白云岩,夹厚度较大的深绿色海绿石页岩;上部为泥质白云岩夹少量薄层含海绿石页岩;顶部见1层红褐色泥质胶结砂砾岩,代表古风化壳残余。铁岭组一段代表风暴浪基面附近沉积,水深波动频繁。铁岭组二段中下部为泥质灰岩夹竹叶状砾屑灰岩(图 2-H)和厚层叠层石灰岩,上部为厚层块状叠层石微晶灰岩(图 2-I)。铁岭组二段主要发育于风暴浪基面之上的浅潮下带环境。

2.3 年代框架

华北长城系和蓟县系是目前全球同期地层年代约束最好的岩石地层单元(图 3)。位于常州沟组底部不整合面之下的侵入环斑花岗岩体的LA-MC-ICP-MS锆石U-Pb年龄为1673±10Ma(Lietal.,2013);串岭沟组底部碎屑锆石U-Pb年龄为1657.4Ma(段超等,2014);团山子组顶部LA-MC-ICP-MS钾质火山岩锆石U-Pb年龄为1637±15Ma(张拴宏等,2013);大红峪组火山岩SHRIMP锆石U-Pb年龄为1622±23Ma和1626±9Ma(高林志等,2008a;Luetal.,2008);蓟县高于庄组三段下部LA-MC-ICP-MS凝灰岩锆石U-Pb年龄为1577±12Ma(田辉等,2015);延庆高于庄组三段上部分别获得凝灰岩的SHRIMP和LA-MC-ICP-MS锆石年龄1559±12Ma和1560±5Ma(李怀坤等,2010);雾迷山组三段凝灰岩SHRIMP锆石U-Pb年龄分别为1487±16Ma和1483±13Ma(李怀坤等,2014);铁岭组斑脱岩SHRIMP锆石U-Pb年龄为1437±21Ma(Suetal.,2010);下马岭组凝灰岩SHRIMP锆石U-Pb年龄为1366±9Ma(高林志等,2008b),且凝灰岩层和斑脱岩高精度TIMS锆石U-Pb年龄分别为1384.4±1.4Ma和1392.2±1.0Ma(Zhangetal.,2015)。依据上述高精度定年数据和地层序列,将高于庄组、雾迷山组、铁岭组的年龄分别估计为1600~1540Ma(李怀坤等,2010,2014)、1520~1470Ma(李怀坤等,2014)和1450~1400Ma(Zhangetal.,2009,2015)(图 3)。

图 3 华北元古宇地层序列和锆石U-Pb年龄(据Tang et al.,2016,有修改)Fig.3 Stratigraphic subdivisions and zircon U-Pb age constraints of the Proterozoic succession in North China Platform(modified from Tang et al.,2016)

3 材料和方法

研究样品分别采自蓟县高于庄组(40°09′2.09″N, 117°28′34.32″E)、凌源大河北村雾迷山组(40°53′21.72″N, 118°57′23.64″E)、野三坡雾迷山组(39°39′58.37″N, 115°28′02.81″E)和天津铁岭子村铁岭组(40°05′29.21″N, 117°23′53.63″E)(图 1)。共采集碳酸盐岩样品84份,磨制探针片40张,对84份样品进行了I/(Ca+Mg)值测试分析。

宏观沉积特征主要基于野外露头观察,薄片微观特征使用Zeiss Scope A1偏光显微镜观察,超微构造使用Zeiss Supra 55型场发射扫描电镜分析,其中SE2探头用于获取二次电子图像,AsB探头用于获取背散射电子图像。I/(Ca+Mg)值测试方法据Shang等(2019),简述如下:称取200目样品粉末约5mg,用超纯(MQ)水润洗4次去除黏土矿物(Tangetal.,2017b)和可溶性盐;润洗样品离心干燥后在玛瑙钵中碾细,再次称重;用3%硝酸充分溶解样品40min,然后离心,分取2次上清液,用于主量元素和碘测试。主量元素测试取0.2mL上清液,用3%HNO3稀释至1︰51000;碘测试取1mL上清液,添加3%叔胺溶液,然后用MQ水稀释至0.5%以抑制溶液中的碘挥发(Luetal.,2010;Hardistyetal.,2017)。为了进一步避免碘的流失,实验需在48 h内测试完成。主量元素和碘元素测试均在国家地质实验测试中心完成,其中主量元素使用PerkinElmer NexION 300Q电感耦合等离子体质谱仪(ICP-MS)测试,JDo-1标样监测显示测试误差小于5%;碘元素采用MC-ICP-MS(Neptune Plus,Thermo Fisher Scientific,Germany)测试,标样GSR-12监测显示测量误差小于6%(1σ)(Shangetal.,2019),Ⅰ/(Ca+Mg)值的检测限约为0.1μmol/mol。

4 结果

4.1 碳酸盐灰泥和海底沉淀特征

4.1.1 宏观特征

在研究区,灰泥集中发育在高于庄组三段、雾迷山组四段以及铁岭组二段(图 3;图 4)。野外观察发现,在灰泥集中发育的层位,纤维状文石海底沉淀往往不发育。高于庄组三段灰泥层的厚度通常为0.5~3cm,横向厚度较稳定,露头呈灰色,而相邻的含泥白云质灰岩风化面则呈淡黄色(图 4-A);这些灰泥层主要发育在从泥质灰岩向钙质泥岩的过渡层中。雾迷山组四段的灰泥层特征与高于庄组相近,但更加发育(图 4-D),尽管其多与含陆源碎屑的微生物席纹层交互产出,但成分较微生物席更纯净,缺乏陆源碎屑和席纹层;而邻近岩层中可见灰色不连续硅质条带或结核,并常见有风暴砾岩透镜体和软沉积变形。铁岭组二段的灰泥多以厚层叠层石形式产出,与高于庄组和雾迷山组的灰泥层产出形式明显不同(图 4-G):这些灰泥同时构成了叠层石的柱体和柱间充填物(Tosti and Riding,2017a,2017b),叠层石柱体宽窄不一,大部分小于10cm,常有分支,其间由狭长的柱间水道分隔(图 4-G);叠层石纹层隆起较低,纹层之间常呈不完全叠覆,致使纹层纵向发育不稳定,表明叠层石生长过程中受水体扰动明显;叠层石柱体早期矿化不明显,易被流水冲刷形成内碎屑,可见弯曲变形,表明属水柱沉淀灰泥而不是席内早期矿化产物(Tosti and Riding,2017a,2017b)。

以纤维状文石扇形式产出的海底沉淀集中发育在高于庄组四段下部和雾迷山组二段中部。虽然在这些层位有可能发育少量灰泥沉淀,但后者通常并不独立成层。高于庄组四段下部的晶体扇最大直径约20cm,高可达约10cm(图 4-J)。晶体扇密集发育的层段可厚达十余米。在剖面上可见由晶体扇压实形成的“薄饼”(图 4-J),其层面密布文石纤维(图 4-K)。雾迷山组二段中部发育厘米级晶体扇沉积,扇体最大直径约3cm(图 4-M)。它们通常与微指状叠层石、黑色纹层石和微晶白云岩在纵向上相互叠置。文石扇可见扇根,并向上过渡为微指状叠层石(图 4-M),其间可见扁平砾石和波状层理。值得注意的是,文石不稳定,难以在深时记录中保存,而是会转化成为低镁方解石或白云石。本研究中,高于庄组的文石扇实际已转化为方解石扇,雾迷山组文石扇则已转化为白云石扇,它们均是文石扇假晶(见 表 1 中Mg/Ca值)。

A—蓟县高于庄组三段上部灰泥沉淀层,单层厚0.5~3cm,侧向平直连续延伸,呈浅灰色(箭头);B—蓟县高于庄组三段上部球粒灰泥(有重结晶),贫陆源碎屑(单偏光);C—背散射照片,示蓟县高于庄组三段上部灰泥晶粒(浅灰色)“悬浮”在白云石(深灰色)晶粒间;D—凌源雾迷山组四段灰泥沉淀层,单层厚1~2cm,侧向平直连续延伸,呈浅灰色(箭头);E和F—凌源雾迷山组四段灰泥沉淀主要由近球形微晶方解石晶粒组成,重结晶较弱,贫陆源碎屑(单偏光);G—蓟县铁岭组二段叠层石,柱体和柱间充填均由灰泥组成;H和Ⅰ—蓟县铁岭组二段叠层石主要由近球形灰泥晶粒组成,呈麻点状;J—蓟县高于庄组四段下部文石扇(黄色箭头)与微生物席纹层(白色箭头)共同发育,文石扇被压扁(单偏光);K—蓟县高于庄组四段下部文石扇(层面);L—蓟县高于庄组四段下部文石扇,可见纤维状晶体(红色虚线),末端平滑(黄色箭头);M—蓟县高于庄组四段下部“压扁”文石扇纵切面,可见横向展布的纤维状文石;N—野三坡雾迷山组二段文石扇(黄色箭头)和微指状叠层石(白色箭头); O—野三坡雾迷山组二段文石扇“扇根”单偏光显微特征。J-M中文石扇已方解石化,N和O中的文石扇已白云石化图 4 华北高于庄组、雾迷山组和铁岭组碳酸盐岩沉积特征和显微特征Fig.4 Macroscopic and microscopic features of carbonate rocks from the Gaoyuzhuang,Wumishan and Tieling Formations in North China

4.1.2 微观特征

显微观察表明,高于庄组三段灰泥的晶粒呈次圆—圆形,重结晶可导致其粒径大于灰泥标准(5μm)并达到细粉晶级,通常约10μm,少量大于20μm,普遍缺乏微生物席和陆源碎屑(图 4-B,4-C)。雾迷山组的灰泥较纯净、贫陆源碎屑和有机质,少见后期脉体,显示较弱的成岩改造特征;灰泥晶粒大小均一,平均粒径不超过30μm,且大部分表现为近球形(图 4-E,4-F)。铁岭组叠层石柱体与柱间均被灰泥充填,贫生物扰动和陆源碎屑(图 4-H),灰泥晶粒大小均一,通常10~15μm,略大于高于庄组与雾迷山组,但铁岭组的灰泥略显不纯,呈麻点状(图 4-I)。

纤维状文石海底沉淀与灰泥在镜下呈现出截然不同的特征。蓟县高于庄组晶体扇中柱状文石晶体宽约1mm,从晶体底部到顶部,晶体宽度略有增大(图 4-L)。雾迷山组中部文石扇呈向上散开的扇状发育,底部可见扇根,向上宽度增大,内隐约可见垂向生长的文石纤维,单根纤维宽度较难辨识(图 4-N,4-O)。

4.2 地球化学特征

图中问号处缺乏Ce异常数据,据Ⅰ/(Ca+Mg)值为0μmol/mol推测Ce/Ce*值约为1图 5 华北蓟县高于庄组、凌源雾迷山组四段下部和蓟县铁岭组地层柱状图和地球化学特征(据Zhang et al.,2018;孙龙飞等,2020;周泓屹,2020;有修改)Fig.5 Geochemical data and lithostratigraphic column of the Gaoyuzhuang Formation,lower part of Member 4 of Wumishan Formation and Tieling Formation in North China(modified from Zhang et al.,2018;Sun et al.,2020;Zhou,2020)

据本研究收集的大部分研究层段与氧化还原条件相关的地球化学数据分析,蓟县高于庄组三段下部有1次显著的Ce异常负偏,Ce/Ce*值从约1.0转变为约0.8并在三段中—上部以及四段部分地层内持续,但在文石海底沉淀发育层位,Ce异常数据缺失(图 5;Zhangetal.,2018)。凌源雾迷山组四段下部厚约150m的地层内存在明显的Ce负异常,Ce/Ce*值为约0.8(孙龙飞等,2020)。蓟县铁岭组二段Ce异常持续存在,Ce/Ce*值可低至0.8以下;短暂的Cr同位素正异常也指示在铁岭组二段沉积期,大气存在短暂的增氧过程(Weietal.,2021)。蓟县铁岭组二段具有较高的I/(Ca+Mg)值,最高可达3.15μmol/mol,其中大于0.5μmol/mol的样品占比为22/35。

本研究进一步分析了高于庄组四段和雾迷山组二段文石海底沉淀产出层位的氧化还原地球化学数据,发现在蓟县高于庄组四段的21个文石海底沉淀样品中,仅有2个样品的碘含量分别为0.07 μg/g和0.03 μg/g,其余均无信号检出(表 1)。样品中Sr含量较高,最高可达1388 μg/g,最低值为40 μg/g,平均值598 μg/g。Mg/Ca摩尔比值最高为0.85,最低为0.01,平均值为0.11。野三坡雾迷山组二段的17个样品中,黑色纹层石(由亚毫米级纤维状文石等厚层与微亮晶层交互构成;Tangetal.,2014)样品14个,文石扇样品2个,文石扇紧邻的微指状叠层石样品1个。所有这些测试样品均未检测到碘信号,Mg/Ca摩尔比值最高为1.02,最低为0.95,平均值为0.98;Sr含量最高30 μg/g,最低10 μg/g,平均值为23.81 μg/g;Mn/Sr摩尔比值最高2.23,最低0.51,平均值为0.93。由于碳酸盐沉淀抑制剂在碳酸盐沉淀过程中一般会被排出碳酸盐晶格(Sumner and Grotzinger,1996),而且Fe、Mn含量因容易受到早期成岩过程影响而增加(Tangetal.,2018;Fangetal.,2020),因此,笔者并未针对性地开展不同类型碳酸盐沉淀的Fe、Mn含量分析。

5 讨论

5.1 华北中元古代浅海碳酸盐沉淀方式

5.1.1 海底沉淀

海底沉淀和水柱灰泥沉淀是前寒武纪碳酸盐岩中最引人注目的2种沉淀方式(Sumner and Grotzinger,1996)。碳酸盐海底沉淀的产出形式主要包括纤维状文石扇(Grotzinger,1989;Grotzinger and Kasting,1993;Grotzinger and James,2000;Sumner and Grotzinger,2000,2004;Tangetal.,2014,2015)、微指状叠层石(Hofmann and Jackson,1987;Tangetal.,2013)和鱼骨状方解石(Sumner and Grotzinger,1996,2000;Grotzinger and James,2000;汤冬杰等,2017)。这些海底沉淀一般垂直层面生长,晶体常具纤维状形态,其内缺乏碎屑混入,从而显著区别于相邻的其他沉积。在本研究中,蓟县高于庄组四段的纤维状文石扇特征在层面上十分典型(图 4-K),但这些晶体扇常被压扁,在剖面上呈厘米至分米级透镜体,较难辨识(图 4-J)。由于这些文石扇较围岩颜色更深,曾被称为“沥青质”(天津地质矿产局,1992),实则为压扁的纤维状文石扇海底沉淀(谢树成等,2016)。野三坡雾迷山组二段的纤维状文石扇内可见“扇根”,内部纯净,垂向纤维状晶体虽受重结晶影响但仍清晰可见,属典型的纤维状文石扇(图 4-M)。这种晶体扇高度近10cm,与古元古代典型文石扇的大小相当(Sumner and Grotzinger,2000,2004)。

一般认为纤维状文石扇原始沉淀的矿物为文石,由于文石不稳定,在成岩阶段可转化为方解石或白云石(Hood and Wallace,2012,2015)。但也有研究认为这些文石海底沉淀可能并非碳酸盐沉淀,而是由石膏晶体转变而成(Holland,1984;Hofmannetal.,1985)。然而,由于前寒武纪大气整体低氧,有氧风化输入到海洋的硫酸根通量极低(Luoetal.,2015),海水以缺氧、铁化为主,因此不易形成石膏沉淀。另一方面,高于庄组文石晶体末端平滑(图 4-L),为典型的文石特征,与石膏或方解石的茅状末端明显不同。

由于海底沉淀内部较围岩显著缺乏碎屑沉积,且碎屑沉积会导致其生长终止,因此海底沉淀通常被认为是碳酸盐快速沉淀的标志(Grotzinger and Kasting,1993)。文中研究的文石海底沉淀矿物纯净,缺乏陆源碎屑,且不含微生物席纹层。由于微生物席一般具有快速生长特征,如果条件适宜,数周内便可覆盖整个海岸带(Noffkeetal.,2001),因此这些快速沉淀文石晶体扇的发育反映海水具有高碳酸盐饱和度。

5.1.2 水柱灰泥沉淀

在研究的样品中,灰泥晶粒呈近球状,略有重结晶,直径10~20μm,缺乏破碎和磨圆现象,且缺乏其他碎屑伴生(图 4-A至4-I),表明它们并非机械破碎而成,而很可能是由蓝细菌光合作用诱发的水柱方解石沉淀。在灰泥层相邻的灰质白云岩中可见方解石晶粒“悬浮”于白云石基质内(图 4-C),进一步表明方解石微晶为水柱灰泥沉淀成因。灰泥层内方解石晶粒纯净,缺乏微生物席和碎屑颗粒,从而与围岩形成鲜明对比,表明灰泥与纤维状文石海底沉淀类似,具有快速沉淀的特征,指示海水具有碳酸钙过饱和特征。

5.2 华北中元古代浅海氧化还原条件波动

图 6 华北高于庄组和雾迷山组碳酸盐岩Ⅰ/(Ca+Mg)值与Sr和Mg/Ca值的协变关系Fig.6 Ⅰ/(Ca+Mg)values versus Sr and Mg/Ca values in carbonate rocks of the Gaoyuzhuang and Wumishan Formations in North China

5.3 华北中元古代浅海碳酸盐沉淀的控制因素

前寒武纪碳酸盐海底沉淀丰度降低以及灰泥丰度增加的长期趋势曾被归因为碳酸钙饱和度的持续下降(Grotzinger,1990;Grotzinger and James,2000)。由于陆源碎屑输入可造成文石海底沉淀的生长中断,大尺度(如分米级)文石扇被认为代表了海水具有极高碳酸钙饱和度条件下的快速沉淀产物(Sumner and Grotzinger,2000),灰泥的相对增加则可能表明海水的碳酸盐饱和度有所降低。如前所述,本研究中的灰泥可构成纯净的厘米级灰泥层,与相邻的微生物席层和富碎屑颗粒层形成鲜明对比(图 4-B,4-E,4-H),表明其也具有快速沉淀的特征,反映海水同样具有高碳酸钙饱和度。因此,中元古代生物碳酸盐沉淀在海底沉淀与水柱沉淀之间的频繁转换,并非主要受控于海水碳酸钙饱和度的增加或降低。

蓝细菌的二氧化碳浓缩机制(CCM)被认为是导致灰泥从水柱中沉淀的关键因素(Riding,2006)。由于海水中存在大量且多样的碳酸盐沉淀抑制剂,即使海水碳酸钙过饱和,碳酸盐矿物也很难直接从海水中成核—生长—沉淀(Okuboetal.,2018)。有关蓝细菌二氧化碳CCM启动所需的pCO2临界值和启动时间还存在一定的不确定性。实验研究表明,当pCO2低于10 PAL时(约0.4%),即可触发底栖蓝细菌的CCM启动(Badgeretal.,2002)。已知最早且保存较好的钙化底栖蓝细菌发现于加拿大约1200Ma的Society Cliffs组叠层石内,并被认为是当时大气pCO2降低至10 PAL的重要标志(Kah and Riding,2007)。浮游蓝细菌CCM启动的临界pCO2可能相对较高,约为现代水平的33倍(Arpetal.,2002)。Sherman等(2000)发现在1400~1300Ma,灰泥已在碳酸盐沉积中占据重要比例,故推测浮游蓝细菌CCM启动可能远早于1400Ma(Fralick and Riding,2015)。因此,在中元古代之前浮游蓝细菌的CCM可能已经启动,中元古代碳酸盐海底沉淀与水柱沉淀的交替,可能并非受控于大气pCO2波动,而是受其他因素影响。

5.4 碳酸盐沉淀方式在古氧相分析中的应用价值和适用条件

适度氧化的浅海是早期真核生物的重要生态空间,故研究浅海的氧化还原状态具有重要的意义。由于在前寒武纪大气整体低氧的背景下,浅海的氧化还原状态具有显著的时空动态波动和不均一性(Poultonetal.,2010;Sperlingetal.,2014;Gilleaudeau and Kah,2015;Reinhardetal.,2016;Wangetal.,2020),因此开展长序列、多剖面的研究是认识这个时期浅海氧化还原条件动态演化的关键。但是这个时期的地层厚度巨大,较难开展高密度的长序列地球化学研究。碳酸盐沉淀方式与海水氧化还原条件关系的确立,为直观、便捷、高效、定性地识别海水氧化还原状态提供了重要方法。这种方法可有效地用于野外初步分析氧化还原条件、为选定进一步地球化学研究的关键层位提供依据。此外,由于碳酸盐岩易受重结晶和成岩改造的影响,对于强烈重结晶和成岩改造的样品,运用地球化学指标存在一定的局限性甚至不能进行有效的地球化学分析,而碳酸盐沉淀方式变化则可以提供较为可靠的判断氧化还原条件的途径。

由于Fe3+/Fe2+(+0.77 V)具有较低的氧化还原电势(Lietal.,2019),当缺氧海水中氧含量增加时,Fe2+就会被氧化而从海水中移除,从而改变碳酸盐的沉淀方式。因此,碳酸盐沉淀方式的变化非常适合反映前寒武纪大气低氧背景下(Planavskyetal.,2014;Coleetal.,2016;Tangetal.,2016;Bellefroidetal.,2018)较弱的氧化还原条件波动。这一特性使得该指标可以灵敏地反映海水轻微的氧化还原波动,但也因此限制了其在显生宙总体高氧背景下的应用。

6 结论

通过对华北中元古界高于庄组、雾迷山组和铁岭组碳酸盐沉淀方式及其对氧化还原条件变化响应机理的分析,得出了以下结论:

1)在高于庄组三段、雾迷山组四段和铁岭组二段发育大量从水柱沉淀的层状灰泥,在高于庄组四段下部和雾迷山组二段中部发现纤维状文石海底沉淀;它们均具有快速沉淀的性质,可反映海水碳酸钙过饱和特征。

2)碳酸盐岩氧化还原状态指标Ⅰ/(Ca+Mg)值和Ce异常的研究表明,层状灰泥沉淀形成于适度氧化的水体条件,而纤维状文石扇海底沉淀形成于缺氧、铁化的底层海水中。对氧化还原敏感的碳酸盐沉淀抑制剂Fe2+和Mn2+是连接水体氧化还原与碳酸盐沉淀方式的桥梁。

3)碳酸盐沉淀方式(水柱沉淀和海底沉淀)广泛适用于整体低氧背景下的前寒武纪碳酸盐岩地层的氧化还原状态分析。

致谢感谢中国地质大学(北京)研究生谢宝增在样品采集及尚墨翰、李杨在样品测试中提供的帮助,感谢中国科学院地质与地球物理研究所周锡强老师对文章提出的宝贵修改建议。

参考文献(References)

陈晋镳,张惠民,朱士兴,赵震,王振刚. 1980. 蓟县震旦亚界的研究. 见: 中国地质科学院天津地质矿产研究所编. 中国震旦亚界. 天津: 天津科学技术出版社,56-114. [Chen J Z,Zhang H M,Zhu S X,Zhao Z,Wang Z G. 1980. The study of Sinian subboundary in Ji-xian County. In: Tianjin Institute of Geology and Mineral Resources,Chinese Academy of Geological Sciences(ed). Sinian Subboundary in China. Tianjin: Tianjin Science and Technology Press,56-114]

段超,李延河,魏明辉,杨云,侯可军,陈小丹,邹斌. 2014. 河北宣化姜家寨铁矿床串岭沟组底部碎屑锆石LA-MC-ICP-MS U-Pb年龄及其地质意义. 岩石学报, 30(1): 35-48. [Duan C,Li Y H,Wei M H,Yang Y,Hou K J,Chen X D,Zou B. 2014. U-Pb dating study of detrital zircons from the Chuanlinggou Formation in Jiang-jiazhai iron deposit,North China Craton and its geological significances. Acta Petrologica Sinica, 30(1): 35-48]

高林志,张传恒,尹崇玉,史晓颖,王自强,刘耀明,刘鹏举,唐烽,宋彪. 2008a. 华北古陆中、新元古代年代地层框架SHRIMP锆石年龄新依据. 地球学报, 29(3): 366-376. [Gao L Z,Zhang C H,Yin C Y,Shi X Y,Wang Z Q,Liu Y M,Liu P J,Tang F,Song B. 2008a. SHRIMP ZIRCON ages: basis for refining the chronostratigraphic classification of the Meso- and Neoproterozoic strata in North China old land. Acta Geoscientica Sinica, 29(3): 366-376]

高林志,张传恒,史晓颖,宋彪,王自强,刘耀明. 2008b. 华北古陆下马岭组归属中元古界的锆石SHRIMP年龄新证据. 科学通报, 53(21): 2617-2623. [Gao L Z,Zhang C H,Shi X Y,Song B,Wang Z Q,Liu Y M. 2008b. Mesoproterozoic age for Xiamaling Formation in North China Plate indicated by ZIRCON SHRIMP dating. Chinese Science Bulletin, 53(21): 2665-2671]

高林志,张传恒,刘鹏举,丁孝忠,王自强,张彦杰. 2009. 华北—江南地区中、新元古代地层格架的再认识. 地球学报, 30(4): 433-446. [Gao L Z,Zhang C H,Liu P J,Ding X Z,Wang Z Q,Zhang Y J. 2009. Recognition of Meso- and Neoproterozoic stratigraphic framework in North and South China. Acta Geoscientica Sinica, 30(4): 433-446]

郭文琳,苏文博,张健,李惠民,周红英,李怀坤,Ettensohn F R,Huff W D. 2019. 天津蓟县铁岭组新剖面钾质斑脱岩锆石U-Pb测年及Hf同位素研究. 岩石学报, 35(8): 2433-2454. [Guo W L,Su W B,Zhang J,Li H M,Zhou H Y,Li H K,Ettensohn F R,Huff W D. 2019. Zircon U-Pb dating and Hf isotopes of K-bentonites from the Tieling Formation in a new exposure of the Jixian Section,Tianjin,North China Craton. Acta Petrologica Sinica, 35(8): 2433-2454]

李怀坤,朱士兴,相振群,苏文博,陆松年,周红英,耿建珍,李生,杨峰杰. 2010. 北京延庆高于庄组凝灰岩的锆石U-Pb定年研究及其对华北北部中元古界划分新方案的进一步约束. 岩石学报, 26(7): 2131-2140. [Li H K,Zhu S X,Xiang Z Q,Su W B,Lu S N,Zhou H Y,Geng J Z,Li S,Yang F J. 2010. Zircon U-Pb dating on tuff bed from Gaoyuzhuang Formation in Yanqing,Beijing: further constraints on the new subdivision of the Mesoproterozoic stratigraphy in the northern North China. Acta Petrologica Sinica, 26(7): 2131-2140]

李怀坤,苏文博,周红英,相振群,田辉,杨立公,Huff W D,Ettensohn F R. 2014. 中—新元古界标准剖面蓟县系首获高精度年龄制约: 蓟县剖面雾迷山组和铁岭组斑脱岩锆石SHRIMP U-Pb同位素定年研究. 岩石学报, 30(10): 2999-3012. [Li H K,Su W B,Zhou H Y,Xiang Z Q,Tian H,Yang L G,Huff W D,Ettensohn F R. 2014. The first precise age constraints on the Jixian System of the Meso- to Neoproterozoic Standard Section of China: SHRIMP zircon U-Pb dating of bentonites from the Wumishan and Tieling Formations in the Jixian Section,North China Craton. Acta Petrologica Sinica, 30(10): 2999-3012]

旷红伟,彭楠,罗顺社,岑超,李家华,陈铭培. 2009. 燕山中东部凌源地区雾迷山组MT构造的发现、地质特征和研究意义. 自然科学进展, 19(12): 1308-1318. [Kuang H W,Peng N,Luo S S,Cen C,Li J H,Chen M P. 2009. Discovery of MT structure and its geological features and studying significance in the eastern Yanshan in Lingyuan,Liaoning Province. Progress in Natural Science, 19(12): 1308-1318]

旷红伟,柳永清,范正秀,彭楠,许欢,安伟,王能盛,耿元生,朱志才,夏晓旭,王玉冲. 2018. 扬子克拉通北缘中元古界神农架群沉积特征. 古地理学报, 20(4): 523-544. [Kuang H W,Liu Y Q,Fan Z X,Peng N,Xu H,An W,Wang N S,Geng Y S,Zhu Z C,Xia X X,Wang Y C. 2018. Sedimentary characteristics of the Mesopro-terozoic Shennongjia Group in northern margin of Yangtze Craton. Journal of Palaeogeography(Chinese Edition), 20(4): 523-544]

陆松年,李惠民. 1991. 蓟县长城系大红峪组火山岩的单颗粒锆石U-Pb法准确定年. 地球学报, 12(1): 137-146. [Lu S N,Li H M. 1991. A precise U-Pb single zircon age determination for the volcanics of Dahongyu Formation. Acta Geoscientica Sinica, 12(1): 137-146]

罗顺社,张建坤,陈小军,旷红伟. 2010. 辽西凌源地区雾迷山组沉积特征与层序地层. 中国地质, 37(2): 394-403. [Luo S S,Zhang J K,Chen X J,Kuang H W. 2010. Sedimentary characteristics and sequence stratigraphy of Wumishan Formation in Lingyuan area,western Liaoning Province. Chinese Geology, 37(2): 394-403]

梅冥相. 2005. 天津蓟县剖面中元古界高于庄组臼齿状构造的层序地层位置及其成因的初步研究. 古地理学报, 7(4): 437-447. [Mei M X. 2005. Preliminary study on sequence-stratigraphic position and origin for molar-tooth structure of the Gaoyuzhuang Formation of Mesoproterozoic at Jixian in Tianjin. Journal of Palaeogeography(Chinese Edition), 7(4): 437-447]

梅冥相. 2007. 燕山地区中元古代高于庄组非叠层石碳酸盐岩序列的沉积特征及其重要意义. 现代地质, 21(1): 45-56. [Mei M X. 2007. Sedimentary features and their implication for the depositional succession of non-stromatolitic carbonates, Mesoproterozoic Gaoyuzhuang Formation in Yanshan area of North China. Geoscience, 21(1): 45-56]

乔秀夫,高林志,张传恒. 2007. 中朝板块中、新元古界年代地层柱与构造环境新思考. 地质通报, 26(5): 503-509. [Qiao X F,Gao L Z,Zhang C H. 2007. New idea of the Meso- and Neoproterozoic chronostratigraphic chart and tectonic environment in Sino-Korean Plate. Geological Bulletin of China, 26(5): 503-509]

孙龙飞,汤冬杰,周利敏,方浩,吴孟亭,郭华,周锡强,邹佳男,史晓颖. 2020. 华北中元古界雾迷山组浅海脉冲式增氧. 古地理学报, 22(6): 1181-1196. [Sun L F,Tang D J,Zhou L M,Fang H,Wu M T,Guo H,Zhou X Q,Zou J N,Shi X Y. 2020. A pulsed oxygenation in shallow seawater recorded by Mesoproterozoic Wumishan Formation,North China. Journal of Palaeogeography(Chinese Edition), 22(6): 1181-1196]

苏文博. 2014.2012年全球前寒武纪新年表与中国中元古代年代地层学研究. 地学前缘, 21(2): 119-138. [Su W B. 2014. A review of the revised Precambrian Time Scale(GTS2012)and the research of the Mesoproterozoic chronostratigraphy of China. Earth Science Frontiers, 21(2): 119-138]

汤冬杰,史晓颖,张文浩,刘云,吴金键. 2017. 华北中元古代鱼骨状方解石: 成因机制和古环境意义. 古地理学报, 19(2):227-240. [Tang D J,Shi X Y,Zhang W H,Liu Y,Wu J J. 2017. Mesopro-terozoic herringbone calcite from North China Platform: ge-nesis and paleoenvironmental significance. Journal of Palaeogeography(Chinese Edition), 19(2): 227-240]

天津地质矿产局. 1992. 天津市区域地质志. 北京: 地质出版社. [Tianjin Bureau of Geology and Mineral Resources. 1992. Regional Geology of Tianjin. Beijing: Geological Publishing House]

田辉,张健,李怀坤,苏文博,周红英,杨立公,相振群,耿建珍,刘欢,朱士兴,许振清. 2015. 蓟县中元古代高于庄组凝灰岩锆石LA-MC-ICPMS U-Pb定年及其地质意义. 地球学报, 36(5): 647-658. [Tian H,Zhang J,Li H K,Su W B,Zhou H Y,Yang L G,Xiang Z Q,Geng J Z,Liu H,Zhu S X,Xu Z Q. 2015. Zircon LA-MC-ICPMS U-Pb dating of tuff from Mesoproterozoic Gaoyuzhuang Formation in Jixian County of North China and its geological significance. Acta Geoscientica Sinica, 36(5): 647-658]

谢树成,颜佳新,史晓颖,殷鸿福,等. 2016. 烃源岩地球生物学. 北京: 科学出版社,83-87. [Xie S C,Yan J X,Shi X Y,Yin H F,etal. 2016. Geobiology of Hydrocarbon Source Rocks. Beijing: Science Press,83-87]

张拴宏,赵越,叶浩,胡健民,吴飞. 2013. 燕辽地区长城系串岭沟组及团山子组沉积时代的新制约. 岩石学报, 29(7): 2481-2490. [Zhang S H,Zhao Y,Ye H,Hu J M,Wu F. 2013. New constraints on ages of the Chuanlinggou and Tuanshanzi formations of the Changcheng System in the Yan-Liao area in the northern North China Craton. Acta Petrologica Sinica, 29(7): 2481-2490]

周弘屹. 2020. 华北陆表海中元古代铁岭组沉积期氧化还原状态. 中国地质大学(北京)本科学位论文. [Zhou H Y. 2020. Shallow seawater redox conditions during the deposition of the Mesoproterozoic Tieling Formation,North China Land Surface Sea. Undergraduate dissertation of China University of Geoscience(Beijing)]

Ahm A S C,Bjerrum C J,Blättler C L,Swart P K,Higgins J A. 2018. Quantifying early marine diagenesis in shallow-water carbonate sediments. Geochimica et Cosmochimica Acta, 236(1): 140-159.

Arp G,Reimer A,Reitner J. 2002. Calcification of cyanobacterial filaments. Girvanella and the origin of lower Paleozoic lime mud. Comment and reply: comment. Geology, 30(6): 579-580.

Badger M R,Hanson D,Price G D. 2002. Evolution and diversity of CO2concentrating mechanisms in cyanobacteria. Functional Plant Biology, 29: 161-173.

Badger M R,Price G D. 2003. CO2concentrating mechanisms in cyanobacteria: molecular components,their diversity and evolution. Journal of Experimental Botany, 54(383): 609-622.

Bellefroid E J,Hood A S,Hoffman P F,Thomas M D,Reinhard C T,Planavsky N J. 2018. Constraints on Paleoproterozoic atmospheric oxygen levels. Proceedings of the National Academy of Sciences of the United States of America, 115(32): 8104-8109.

Byrne R,Sholkovitz E. 1996. Marine chemistry and geochemistry of the lanthanides. In: Gschneider K A Jr,Eyring L R(eds). Handbook on the Physics and Chemistry of the Rare Earths,23. Amsterdam: Elsevier,497-593.

Canfield D E,Zhang S,Frank A B,Wang X,Wang H,Su J,Ye Y,Frei R. 2018. Highly fractionated chromium isotopes in Mesoproterozoic-aged shales and atmospheric oxygen. Nature Communications, 9(1): 2871.

Chu X,Zhang T,Zhang Q,Lyons T. 2007. Sulfur and carbon isotope records from 1700 to 800Ma carbonates of the Jixian section,northern China: implications for secular isotope variations in Proterozoic seawater and relationships to global supercontinental events. Geochimica et Cosmochimica Acta, 71(19): 4668-4692.

Cole D B,Reinhard C T,Wang X,Gueguen B,Halverson G P,Gibson T,Hodgskiss M S W,McKenzie N R,Lyons T W,Planavsky N J. 2016. A shale-hosted Cr isotope record of low atmospheric oxygen during the Proterozoic. Geology, 44(7): 555-558.

Fang H,Tang D,Shi X,Lechte M,Yu W. 2020. Manganese-rich deposits in the Mesoproterozoic Gaoyuzhuang Formation(ca. 1.58Ga),North China platform: genesis and paleoenvironmental implications. Palaeo-geography,Palaeoclimatology,Palaeoecology, 559: 109966.

Fralick P,Riding R. 2015. Steep rock lake: sedimentology and geochemi-stry of an Archean carbonate platform. Earth-Science Reviews, 151: 132-175.

German C R,Elderfield H. 1990. Application of the Ce anomaly as a paleoredox indicator: the ground rules. Paleoceanography, 5(5): 823-833.

German C R,Holliday B P,Elderfield H. 1991. Redox cycling of rare earth elements in the suboxic zone of the Black Sea. Geochimica et Cosmochimica Acta, 55(12): 3553-3558.

Gilleaudeau G J,Kah L C. 2015. Heterogeneous redox conditions and a shallow chemocline in the Mesoproterozoic ocean: evidence from carbon-sulfur-iron relationships. Precambrian Research, 257: 94-108.

Gilleaudeau G J,Frei R,Kaufman A J,Kah L C,Azmy K,Bartley J K,Chernyavskiy P,Knoll A H. 2016. Oxygenation of the Mesoproterozoic atmosphere: clues from chromium isotopes in carbonates. Geochemical Perspectives Letters, 2(2): 178-187.

Gischler E,Dietrich S,Harris D,Webster J M,Ginsburg R N. 2013. A comparative study of modern carbonate mud in reefs and carbonate platforms: mostly biogenic,some precipitated. Sedimentary Geology, 292(15): 36-55.

Grotzinger J P. 1989. Facies and evolution of Precambrian carbonate depo-sitional systems: emergence of the modern platform archetype. SEPM(Society for Sedimentary Geology)Special Publication, 44: 79-106.

Grotzinger J P. 1990. Geochemical model for Proterozoic stromatolite decline. American Journal of Science,290-A: 80-103.

Grotzinger J P,Kasting J F. 1993. New constraints on Precambrian ocean composition. The Journal of Geology, 101(2): 235-243.

Grotzinger J P,James N P. 2000. Precambrian carbonates: evolution of understanding. SEPM(Society for Sedimentary Geology)Special Publication, 67: 3-20.

Guo H,Du Y,Kah L C,Huang J,Hu C,Huang H,Yu W. 2013. Isotopic composition of organic and inorganic carbon from the Mesoproterozoic Jixian Group,North China: implications for biological and oceanic evolution. Precambrian Research, 224: 169-183.

Guo H,Du Y,Kah L C,Hu C,Huang J,Huang H,Yu W,Song H. 2015. Sulfur isotope composition of carbonate-associated sulfate from the Mesoproterozoic Jixian Group,North China: implications for the marine sulfur cycle. Precambrian Research, 266: 319-336.

Hardisty D S,Lu Z,Planavsky N J,Bekker A,Philippot P,Zhou X,Lyons T W. 2014. An iodine record of Paleoproterozoic surface ocean oxygenation. Geology, 42(7): 619-622.

Hardisty D S,Lu Z,Bekker A,Diamond C W,Gill B C,Jiang G,Kah L C,Knoll A H,Loyd S J,Osburn M R,Planavsky N J,Wang C,Zhou X,Lyons T W. 2017. Perspectives on Proterozoic surface ocean redox from iodine contents in ancient and recent carbonate. Earth and Planetary Science Letters, 463(1): 159-170.

Higgins J A,Fischer W W,Schrag D P. 2009. Oxygenation of the ocean and sediments: consequences for the seafloor carbonate factory. Earth and Planetary Science Letters, 284(1): 25-33.

Higgins J A,Blättler C L,Lundstrom E A,Santiago-Ramos D P,Akhtar A A,Crüger Ahm A S,Bialik O,Holmden C,Bradbury H,Murray S T,Swart P K. 2018. Mineralogy,early marine diagenesis,and the chemistry of shallow-water carbonate sediments. Geochimica et Cosmochimica Acta, 220: 512-534.

Hofmann H J,Thurston P C,Wallace H. 1985. Archean stromatolites from Uchi greenstone belt,northwestern Ontario. In: Evolution of Archean Supracrustal Sequences. Newfoundland: GAC St. Johns, 125-132.

Hofmann H J,Jackson G D. 1987. Proterozoic ministromatolites with radial-fibrous fabric. Sedimentology, 34(6): 963-971.

Holland H D. 1984. The Chemical Evolution of the Atmosphere and Oceans. Princeton,New Jersey: Princeton University Press,582.

Hood A,Wallace M W. 2012. Synsedimentary diagenesis in a Cryogenian reef complex: ubiquitous marine dolomite precipitation. Sedimentary Geology, 255-256: 56-71.

Hood A,Wallace M W. 2015. Extreme ocean anoxia during the Late Cryogenian recorded in reefal carbonates of Southern Australia. Precambrian Research, 261: 96-111.

Kaczmarek S E,Sibley D F. 2007. A comparison of nanometer-scale growth and dissolution features on natural and synthetic dolomite crystals: implications for the origin of dolomite. Journal of Sedimentary Research, 77(5): 424-432.

Kah L C,Riding R. 2007. Mesoproterozoic carbon dioxide levels inferred from calcified cyanobacteria. Geology, 35(9): 799-802.

Kaufman A J,Knoll A H. 1995. Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications. Precambrian Research, 73(1-4): 27-49.

Knoll A H,Swett K. 1990. Carbonate deposition during the late Proterozoic Era: an example from Spitsbergen. American Journal of Science, 290: 104-132.

Kuang H W,Liu Y Q,Peng N,Luo S S,Li J H,Cen C,Chen M P. 2012. Molar-tooth structure from the Mesoproterozoic Wumishan Formation in Lingyuan,Yanshan region,North China,and geological implications. Acta Geologica Sinica-English Edition, 86(1): 85-95.

Li C,Peng P,Sheng G,Fu J,Yan Y. 2003. A molecular and isotopic geochemical study of Meso- to Neoproterozoic(1.73-0.85Ga)sediments from the Jixian section,Yanshan Basin,North China. Precambrian Research, 125(3-4): 337-356.

Li H,Lu S,Su W,Xiang Z,Zhou H,Zhang Y. 2013. Recent advances in the study of the Mesoproterozoic geochronology in the North China Craton. Journal of Asian Earth Sciences, 72: 216-227.

Li X,Liu L,Wu Y,Liu T. 2019. Determination of the redox potentials of solution and solid surface of Fe(Ⅱ)associated with iron oxyhydro-xides. ACS Earth and Space Chemistry, 3(5): 711-717.

Li Z,Bogdanova S,Collins A,Davidson A,De Waele B,Ernst R E,Fitzsimons I C W,Fuck R A,Gladkochub D P,Jacobs J,Karlstrom K E,Lu S,Natapov L M,Pease V,Pisarevsky S A,Thrane K,Vernikovsky V. 2008. Assembly,configuration,and break-up history of Rodinia: a synthesis. Precambrian Research, 160(1-2): 179-210.

Lin Y,Tang D,Shi X,Zhou X,Huang K. 2019. Shallow-marine ironstones formed by microaerophilic iron-oxidizing bacteria in terminal Paleoproterozoic. Gondwana Research, 76: 1-18.

Ling H F,Chen X,Li D A,Wang D,Shields-Zhou G A,Zhu M. 2013. Cerium anomaly variations in Ediacaran-earliest Cambrian carbonates from the Yangtze Gorges area,South China: implications for oxygena-tion of coeval shallow seawater. Precambrian Research, 225: 110-127.

Liu X M,Kah L C,Knoll A H,Cui H,Wang C,Bekker A,Hazen R M. 2021. A persistently low level of atmospheric oxygen in Earth’s middle age. Nature Communications, 12(1): 1-7.

Lu S,Yang C,Li H K,Li H M. 2002. A group of rifting events in the terminal Paleoproterozoic in the North China Craton. Gondwana Research, 5(1): 123-131.

Lu S,Zhao G,Wang H,Hao G. 2008. Precambrian metamorphic basement and sedimentary cover of the North China Craton: a review. Precambrian Research, 160(1-2): 77-93.

Lu W,Wörndle S,Halverson G P,Zhou X,Bekker A,Rainbird R H,Hardisty D S,Lyons T W,Lu Z. 2017. Iodine proxy evidence for increased ocean oxygenation during the Bitter Springs Anomaly. Geochemical Perspectives Letters, 5: 53-57.

Lu W,Ridgwell A,Thomas E,Hardisty D S,Luo G,Algeo T J,Saltzman M R,Gill B C,Shen Y,Ling H F. 2018. Late inception of a resiliently oxygenated upper ocean. Science, 361(6398): 147-177.

Lu Z,Jenkyns H C,Rickaby R E. 2010. Iodine to calcium ratios in marine carbonate as a paleo-redox proxy during oceanic anoxic events. Geology, 38(12): 1107-1110.

Luo G,Hallmann C,Xie S,Ruan X,Summons R E. 2015. Comparative microbial diversity and redox environments of black shale and stroma-tolite facies in the Mesoproterozoic Xiamaling Formation. Geochimica et Cosmochimica Acta, 151: 150-167.

Meyer H J. 1984. The influence of impurities on the growth rate of calcite. Journal of Crystal Growth, 66(3): 639-646.

Noffke N,Gerdes G,Klenke T,Krumbein W E. 2001. Microbially induced sedimentary structures: a new category within the classification of primary sedimentary structures. Journal of Sedimentary Research, 71(5): 649-656.

Okubo J,Klyukin Y I,Warren L V,Bodnar R J,Xiao S. 2018. The Origin of Barite in the Basal Ediacaran Sete Lagoas Cap Carbonate(bambui Group,Brazil)and Its Implications. In: GSA Annual Meeting in IndianapoLis,Indiana,USA-2018.

Planavsky N J,Reinhard C T,Wang X,Thomson D,McGoldrick P,Rainhard R H,Johnson T,Fischer W W,Lyons T W. 2014. Low Mid-Proterozoic atmospheric oxygen levels and the delayed rise of animals. Science, 346(6209): 635-638.

Poulton S W,Fralick P W,Canfield D E. 2010. Spatial variability in oceanic redox structure 1.8 billion years ago. Nature Geoscience, 3(7): 486-490.

Raven J A. 1997. Putting the C in phycology. European Journal of Phycology, 32(4): 319-333.

Reinhard C T,Planavsky N J,Olson S L,Lyons T W,Erwin D H. 2016. Earth’s oxygen cycle and the evolution of animal Life. Proceedings of the National Academy of Sciences of the United States of America, 113(32): 8933-8938.

Riding R. 2006. Cyanobacterial calcification,carbon dioxide concentrating mechanisms,and Proterozoic-Cambrian changes in atmospheric composition. Geobiology, 4(4): 299-316.

Sami T T,James N P. 1994. Peritidal carbonate platform growth and cyclicity in an early Proterozoic foreland basin,Upper Pethei Group,northwest Canada. Journal of Sedimentary Research,64(2b): 111-131.

Shang M,Tang D,Shi X,Zhou L,Zhou X,Song H,Jiang G. 2019. A pulse of oxygen increase in the early Mesoproterozoic ocean at ca. 1.57-1.56Ga. Earth and Planetary Science Letters, 527: 115797.

Sherman A G,James N P,Narbonne G M. 2000. Sedimentology of a late Mesoproterozoic muddy carbonate ramp,northern Baffin Island,Arctic Canada. In: Grotzinger J P,James N P(eds). Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World. SEPM Special Publication, 67: 275-294.

Sperling E A,Rooney A D,Hays L,Sergeev V N,Vorob’eva N G,Sergeeva N D,Selby D,Johnston D T,Knoll A H. 2014. Redox heterogeneity of subsurface waters in the Mesoproterozoic ocean. Geobiology, 12(5): 373-386.

Su W,Li H,Huff W,Ettensohn F,Zhang S,Zhou H,Wan Y. 2010. SHRIMP U-Pb dating for a K-bentonite bed in the Tieling Formation,North China. Chinese Science Bulletin, 55(29): 3312-3323.

Sumner D Y,Grotzinger J P. 1996. Were kinetics of Archean calcium carbonate precipitation related to oxygen concentration?Geology, 24: 119-122.

Sumner D Y,Grotzinger J P. 2000. Late archean aragonite precipitation: petrography,facies associations,and environmental significance. In: Grotzinger J P, James N P(eds). Carbonates Sedimentation and Dia-genesis in the Evolving Precambrian World. SEPM Special Publication, 67: 123-144.

Sumner D Y,Grotzinger J P. 2004. Implications for Neoarchaean ocean chemistry from primary carbonate mineralogy of the Campbellrand-Malmani Platform,South Africa. Sedimentology, 51(6): 1273-1299.

Tang D,Shi X,Jiang G,Pei Y,Zhang W,Wang Y,Liu M. 2013. Environment controls on Mesoproterozoic thrombolite morphogenesis: a case study from the North China Platform. Journal of Palaeogeography, 2(3): 275-296.

Tang D,Shi X,Jiang G. 2014. Sunspot cycles recorded in Mesoproterozoic carbonate biolaminites. Precambrian Research, 248: 1-16.

Tang D,Shi X,Liu D,Lin Y,Zhang C,Song G,Wu J. 2015. Terminal Paleoproterozoic ooidal ironstone from North China: a sedimentary response to the initial breakup of Columbia supercontinent. Earth Science: Journal of China University of Geosciences, 40: 290-304.

Tang D,Shi X,Wang X,Jiang G. 2016. Extremely low oxygen concentration in Mesoproterozoic shallow seawaters. Precambrian Research, 276: 145-157.

Tang D,Shi X,Jiang G,Zhou X,Shi Q. 2017a. Ferruginous seawater facilitates the transformation of glauconite to chamosite: an example from the Mesoproterozoic Xiamaling Formation of North China. American Mineralogist, 102(11): 2317-2332.

Tang D,Shi X,Ma J,Jiang G,Zhou X,Shi Q. 2017b. Formation of shallow-water glaucony in weakly oxygenated Precambrian ocean: an example from the Mesoproterozoic Tieling Formation in North China. Precambrian Research, 294: 214-229.

Tang D,Shi X,Jiang G,Wu T,Ma J,Zhou X. 2018. Stratiform siderites from the Mesoproterozoic Xiamaling Formation in North China: genesis and environmental implications. Gondwana Research, 58: 1-15.

Tang D,Ma J,Shi X,Lechte M,Zhou X. 2020. The formation of marine red beds and iron cycling on the Mesoproterozoic North China Platform. American Mineralogist, 105(9): 1412-1423.

Thompson J B,Schultze-Lam S,Beveridge T J,Marais D J D. 1997. Whiting events: biogenic origin due to the photosynthetic activity of cyanobacterial picoplankton. Limnology and Oceanography, 42(1): 133-141.

Tosti F,Riding R. 2017a. Fine-grained agglutinated elongate columnar stromatolites: Tieling Formation,ca 1420Ma,North China. Sedimentology, 64(4): 871-902.

Tosti F,Riding R. 2017b. Current molded,storm damaged,sinuous columnar stromatolites: Mesoproterozoic of northern China. Palaeogeography,Palaeoclimatology,Palaeoecology, 465: 93-102.

Wan B,Tang Q,Pang K,Wang X,Bao Z,Meng F,Zhou C,Yuan X,Hua H,Xiao S. 2019. Repositioning the Great Unconformity at the southeastern margin of the North China Craton. Precambrian Research, 324: 1-17.

Wang H,Zhang Z,Li C,Algeo T J,Cheng M,Wang W. 2020. Spatiotemporal redox heterogeneity and transient marine shelf oxygenation in the Mesoproterozoic ocean. Geochimica et Cosmochimica Acta, 270: 201-217.

Wei W,Frei R,Klaebe R,Tang D,Wei G Y,Li D,Tian L L,Huang F,Ling H F. 2021. A transient swing to higher oxygen levels in the atmosphere and oceans at~1.4Ga. Precambrian Research, 354: 106058.

Wörndle S,Crockford P W,Kunzmann M,Bui T H,Halverson G P. 2019. Linking the Bitter Springs carbon isotope anomaly and early Neopro-terozoic oxygenation through Ⅰ/[Ca+Mg]ratios. Chemical Geology, 524: 119-135.

Zhao G,Sun M,Wilde S,Li S. 2003. Assembly,accretion and breakup of the Paleo-Mesoproterozoic Columbia supercontinent: records in the North China Craton. Gondwana Research, 6(3): 417-434.

Zhao G,Li S,Sun M,Wilde S A. 2011. Assembly,accretion,and break-up of the Palaeo-Mesoproterozoic Columbia supercontinent: record in the North China Craton revisited. International Geology Review, 53(11-12): 1331-1356.

Zhang K,Zhu X,Wood R A,Shi Y,Gao Z,Poulton S W. 2018. Oxygenation of the Mesoproterozoic ocean and the evolution of complex eukaryotes. Nature Geoscience, 11: 345-350.

Zhang S,Zhao Y,Yang Z,He Z,Wu H. 2009. The 1.35Ga diabase sills from the northern North China craton: implications for breakup of the Columbia(Nuna)supercontinent. Earth and Planetary Science Letters, 288(3-4): 588-600.

Zhang S,Li Z,Evans D,Wu H,Li H,Dong J. 2012. Pre-Rodinia supercontinent Nuna shaping up: a global synthesis with new paleomagnetic results from North China. Earth and Planetary Science Letters, 353: 145-155.

Zhang S,Wang X,Hammarlund E,Wang H,Costa M,Bjerrum C,Connelly J,Zhang B,Bian L,Candield D. 2015. Orbital forcing of climate 1.4 billion years ago. Proceedings of the National Academy of Sciences of the United States of America, 112(12): E1406-E1413.

Zhang S,Wang X,Wang H,Bjerrum C J,Hammarlund E U,Costa M M,Connelly J N,Zhang B,Su J,Canfield D E. 2016. Sufficient oxygen for animal respiration 1,400million years ago. Proceedings of the National Academy of Sciences, 113(7): 1731-1736.

Zhou X,Jenkyns H C,Owens J D,Junium C K,Zheng X Y,Sageman B B,Hardisty D S,Lyons T W,Ridgwell A,Lu Z. 2015. Upper ocean oxygenation dynamics from Ⅰ/Ca ratios during the Cenomanian-Turonian OAE 2. Paleoceanography, 30(5): 510-526.

猜你喜欢
文石蓟县铁岭
铁岭石油花样多
醍醐灌顶
铁岭雷锋纪念馆
文石瑰意琦行,皴纹超然出众
——详解淄博文石皴纹及赏石文化
河北雄安新区蓟县系雾迷山组沉积特征分析
文石韵
文雅清虚 淄博文石
游蓟县梨木台
——纪念上山下乡48周年
铁岭境内辽代州城设立的环境依据研究
美丽的小城铁岭,我的家!