Open AccessGeochemistry of the Late Cretaceous Pandan Formation in Cebu Island, Central Philippines: Sediment contributions from the Australian plate margin during the Mesozoic
Author(s) -
Rodrigo Jerali D.,
GaboRatio Jillian Aira S.,
Queaño Karlo L.,
Fernando Allan Gil S.,
Silva Leopoldo P.,
Yonezu Kotaro,
Zhang Yu
Publication year - 2020
Publication title -
the depositional record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 3
ISSN - 2055-4877
DOI - 10.1002/dep2.103
Subject(s) - geology , felsic , mafic , geochemistry , island arc , basement , back arc basin , cretaceous , forearc , continental arc , sedimentary rock , siliciclastic , passive margin , provenance , volcanic arc , terrane , craton , detritus , sedimentary depositional environment , subduction , volcanic rock , tectonics , paleontology , volcano , rift , civil engineering , engineering , structural basin
The Late Cretaceous Pandan Formation in Cebu Island is one of the oldest sedimentary units in the Central Philippines. The inconsistencies in geological descriptions and interpretation of the depositional environment of the Pandan Formation complicated efforts to determine the origin and tectonic history of the basement of Cebu Island. This study therefore looks into the petrological and geochemical characteristics of the Pandan Formation and their implications for the tectonic development of the Philippine Arc during the late Mesozoic. Petrographic analyses indicate significant contribution from mafic sources with additional inputs from felsic rocks, siliciclastics and metamorphic sources. Enrichment of detrital quartz from felsic volcanic and plutonic rocks, as well as from siliciclastic and metamorphic sources, has shifted the SiO 2 composition of the Pandan clastics from a mafic to a more intermediate source. Whole‐rock geochemical analyses revealed low SiO 2 /Al 2 O 3 = 4.21, low K 2 O/Na 2 O = 1.16, low Th/Sc = 0.13, low Th/U = 2.78, high La/Th = 4.51, significantly low REEs = ca 76.45 ppm and low La N /Yb N = 4.28. A slight negative chondrite‐normalized Eu/Eu* (0.91) anomaly and significantly high PAAS‐normalized positive Eu/Eu* (1.39) values are consistent with derivation from a young undissected magmatic arc terrane. Tectonic discrimination diagrams suggest formation in an oceanic island arc to active margin/collision zone modelled to be located at the oceanic leading edge of Australia. Rapid uplift and erosion of the magmatic arc and older allochthonous blocks gave way to the rapid deposition of the Pandan Formation in the Late Cretaceous at the subequatorial region.