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Petrographic and geochemical evidence for the formation of primary, bacterially induced lacustrine dolomite: La Roda ’white earth’ (Pliocene, central Spain) | |
del Cura, MAG; Calvo, JP; Ordonez, S; Jones, BF; Canaveras, JC | |
通讯作者 | del Cura, MAG |
来源期刊 | SEDIMENTOLOGY |
ISSN | 0037-0746 |
出版年 | 2001 |
卷号 | 48期号:4页码:897-915 |
英文摘要 | Upper Pliocene dolomites (’white earth’) from La Roda, Spain, offer a good opportunity to evaluate the process of dolomite formation in lakes. The relatively young nature of the deposits could allow a link between dolomites precipitated in modern lake systems and those present in older lacustrine formations. The La Roda Mg-carbonates (dolomite unit) occur as a 3.5- to 4-m-thick package of poorly indurated, white, massive dolomite beds with interbedded thin deposits of porous carbonate displaying root and desiccation traces as well as local lenticular gypsum moulds. The massive dolomite beds consist mainly of loosely packed 1- to 2-mum-sized aggregates of dolomite crystals exhibiting poorly developed faces, which usually results in a subrounded morphology of the crystals. Minute rhombs of dolomite are sparse within the aggregates. Both knobbly textures and clumps of spherical bodies covering the crystal surfaces indicate that bacteria were involved in the formation of the dolomites. In addition, aggregates of euhedral dolomite crystals are usually present in some more clayey (sepiolite) interbeds. The thin porous carbonate (mostly dolomite) beds exhibit both euhedral and subrounded, bacterially induced dolomite crystals. The carbonate is mainly Ca-dolomite (51-54 mol% CaCO3), showing a low degree of ordering (degree of ordering ranges from 0.27 to 0.48). Calcite is present as a subordinate mineral in some samples. Sr, Mn and Fe contents show very low correlation coefficients with Mg/Ca ratios, whereas SiO2 and K contents are highly correlated. delta O-18- and delta C-13-values in dolomites range from -3.07 parts per thousand to 5.40 parts per thousand PDB (mean = 0.06, sigma = 1.75) and from -6.34 parts per thousand to -0.39 parts per thousand, PDB (mean = -3.55, sigma = 1.33) respectively. Samples containing significant amounts of both dolomite and calcite do not in general show significant enrichment or depletion in O-18 and C-13 between the two minerals. The correlation coefficient between delta O-18 and delta C-13 for dolomite is extremely low and negative (r = -0.05), whereas it is higher and positive (r = 0.47) for calcite. The lacustrine dolomite deposit from La Roda is interpreted mainly as a result of primary precipitation of dolomite in a shallow, hydrologically closed perennial lake. The lake was supplied by highly saturated HCO3-/CO32- groundwater that leached dolomitic Mesozoic formations. Precipitation of dolomite from alkaline lake waters took place under a semi-arid to and climate. However, according to our isotopic data, strong evaporative conditions were not required for the formation of the La Roda dolomite. A significant contribution by bacteria to the formation of the dolomites is assumed in view of both petrographic and geochemical evidence. |
英文关键词 | dolomite lacustrine deposits petrography Pliocene Spain stable isotopes |
类型 | Article |
语种 | 英语 |
国家 | Spain ; USA |
收录类别 | SCI-E |
WOS记录号 | WOS:000170636500011 |
WOS关键词 | SOUTH-AUSTRALIA ; COORONG REGION ; MICROBIAL MEDIATION ; WESTERN VICTORIA ; DOLOMITIZATION ; LAKES ; SEDIMENTOLOGY ; PRECIPITATION ; CARBONATES ; HOLOCENE |
WOS类目 | Geology |
WOS研究方向 | Geology |
来源机构 | United States Geological Survey |
资源类型 | 期刊论文 |
条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/141775 |
作者单位 | (1)UCM, CSIC, Inst Geol Econ, Madrid, Spain;(2)Univ Complutense, Fac CC Geol, Dpto Petrol & Geoquim, Madrid, Spain;(3)Univ Alicante, Dpto Ciencias Tierra & Medio Ambiente, E-03080 Alicante, Spain;(4)US Geol Survey, Reston, VA 22092 USA |
推荐引用方式 GB/T 7714 | del Cura, MAG,Calvo, JP,Ordonez, S,等. Petrographic and geochemical evidence for the formation of primary, bacterially induced lacustrine dolomite: La Roda ’white earth’ (Pliocene, central Spain)[J]. United States Geological Survey,2001,48(4):897-915. |
APA | del Cura, MAG,Calvo, JP,Ordonez, S,Jones, BF,&Canaveras, JC.(2001).Petrographic and geochemical evidence for the formation of primary, bacterially induced lacustrine dolomite: La Roda ’white earth’ (Pliocene, central Spain).SEDIMENTOLOGY,48(4),897-915. |
MLA | del Cura, MAG,et al."Petrographic and geochemical evidence for the formation of primary, bacterially induced lacustrine dolomite: La Roda ’white earth’ (Pliocene, central Spain)".SEDIMENTOLOGY 48.4(2001):897-915. |
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