Multiphase dolomitization in the Jutana Formation (Cambrian), Salt Range (Pakistan) : evidences from field observations, microscopic studies and isotopic analysis
Khan, S. (Quaid-i-Azam University (Pakistan). Department of Earth Sciences)
Shah, M. M. (Quaid-i-Azam University (Pakistan). Department of Earth Sciences)

Data:	2019
Resum:	Excellent dolomite exposures are observed in the eastern Salt Range (Pakistan), where the Cambrian Jutana Formation consists of two distinct units (i. e. oolitic - pisolitic unit and massive dolomite unit). Field observations revealed that the lower, oolitic-pisolitic unit mostly comprises medium to thick bedded, interlayered brown yellowish dolostone containing ooids/pisoids and faunal assemblages, and grey whitish sandstone with distinct depositional sedimentary features (i. e. trough-, herringbone- and hhummocky crossbedding). The upper massive dolostone unit consists of thick bedded to massive dolostone. These two units are separated by shale. Petrographic studies identified three dolomite types, which include: fine crystalline dolomite (Dol. I), medium-coarse crystalline dolomite (Dol. II) and fracture associated, coarse crystalline dolomite (Dol. III). Stable isotope studies indicate less depleted δ18O values for Dol. I (-6. 44 to -3. 76‰V-PDB), slightly depleted δ18O values for Dol. II (-7. 73 to -5. 24‰V-PDB) and more depleted δ18O values for Dol. III (-7. 29 to -7. 20‰V-PDB). The δ13C values of the three dolomite phases are well within the range of Cambrian sea-water signatures. Furthermore, δ26Mg-δ25Mg signatures (Dol. I; δ26Mg=-1. 19 to -1. 67, δ25Mg=-0. 61 to -0. 86 and Dol. II; δ26Mg=-1. 34 to -1. 59, δ25Mg=-0. 70 to -0. 83) indicate three phases of dolomitization in different diagenetic settings. First, an initial stage of dolomitization during the early Cambrian resulted from altered marine, Mg-rich fluids associated with the mixing zone mechanism. Second, a late stage of dolomitization was associated with burial during late Permian. A third dolomitization phase was related to post-Eocene times.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre i quan aquestes es distribueixin sota la mateixa llicència que regula l'obra original i es reconegui l'autoria.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Cambrian dolomite ; Salt range ; Diagenetic phases ; O/C isotopes ; Mg-isotopes
Publicat a:	Geologica acta, Vol. 17 (2019) , p. 1-18 (Articles) , ISSN 1696-5728

Adreça original: https://revistes.ub.edu/index.php/GEOACTA/article/view/GeologicaActa2019.17.2
Adreça alternativa: https://raco.cat/index.php/GeologicaActa/article/view/350982
DOI: 10.1344/GeologicaActa2019.17.2

18 p, 6.4 MB

El registre apareix a les col·leccions:
Articles > Articles publicats > Geologica acta
Articles > Articles de recerca