Early Cretaceous paleogeography of Korea and Southwest Japan inferred from occurrence of detrital chromian spinels

Abstract

The Sindong Group was deposited in the north-south trending half-graben Nakdong Trough, southern Korean peninsula. The occurrence of detrital chromian spinels from the Jinju Formation of the Sindong Group in the Gyeongsang Basin means that the mafic to ultramafic rocks were exposed in its provenance. The chromian spinels from the Jinju Formation are characterized by extremely low TiO 2 and Fe 3+ . Moreover, their range of Cr# is from 0.45 to 0.80 and makes a single trend with Mg#. The chemistry of chromian spinels implies that the source rocks for chromian spinels were peridotites or serpentinites, which originated in the mantle wedge. To more narrowly constrain their source rocks, the Ulsan and Andong serpentinites exposed in the Gyeongsang Basin were examined petrographically. Chromian spinels in the Andong serpentinite differ from those of the Jinju Formation and those in the Ulsan serpentinite partly resemble them. Furthermore, the Jinju chromian spinel suite is similar to the detrital chromian spinels from the Mesozoic sediments in the Circum-Hida Tectonic zone, which includes the Nagato Tectonic zone in Southwest Japan and the Joetsu Belt in Northeast Japan. This suggests that the basement rocks, which were located along the main fault bounding the eastern edge of the Nakdong Trough, had exposures of peridotite or serpentinite. It is possible that the Nakdong Trough was directly adjacent to the Circum-Hida Tectonic zone before the opening of the Sea of Japan (East Sea).

Provenance Analysis of Lower Cretaceous Sindong Group Sandstones in the Gyeongsang Basin, Korea, Using Integrated Petrography, Quartz Sem-Cathodoluminescence, and Zircon Zr/Hf Analysis

“…Although detailed information was not provided, rounded zircon, tourmaline, rutile, and apatite are also present in Sindong Group sandstones in all areas, and are especially more common in the Nakdong and Hasandong formations, indicative of their derivation from sedimentary cover, consistent with the presence of sedimentary rock fragments. In addition, basic igneous rocks were also exposed locally from the beginning of the Sindong Group deposition, as evidenced by the occurrence of augite, a diagnostic mineral of basic igneous rocks, which is also supported by the occurrence of detrital chromian spinels (Hisada et al 2008; Y.I. Lee unpublished data).…”

Reconstruction of Subduction and Back‐Arc Spreading in the NW Pacific and Aleutian Basin: Clues to Causes of Cretaceous and Eocene Plate Reorganizations

“…Rifting affected a ~100‐ to 150‐km‐wide zone of the western margin of present‐day NE Honshu, leading to extensional basin formation and rapid subsidence (Martin, ; Nakajima, ; Yoshida et al, ). Hisada et al () and S. Kojima et al () suggested that prior to rifting, southwest Japan was located adjacent to the Korean peninsula based on geological correlation. Sillitoe () suggested that SE Korea and SW Japan shared a single metallogenic belt that appears to have been of offset by 200–250 km after its pre‐42 Ma formation and inferred that the belt was displaced along two major dextral strike‐slip faults, the Yangsan and Tsushima‐Goto faults (Figure ).…”

Provenance identification based on EPMA analyses of heavy minerals: Case study of the Toki Sand and Gravel Formation, central Japan

“…Moreover, heavy minerals could be concentrated, but their chemical compositions have the potential to serve as indexes for provenance analysis. Many studies have revealed provenance based on the chemical compositions of heavy minerals, such as chromium spinel (Arai & Hisada, ; Hisada, Arai, & Lee, ; Hisada, Takashima, Arai, & Lee, ) and garnet (Takeuchi, ). However, the methods used in these studies are inconvenient for the following three reasons: (i) specific skills for mineral identification are needed; (ii) the methods are applicable to limited types of rocks, including target minerals; and (iii) extraction and concentration of target minerals are time‐consuming when large quantities of samples are employed.…”

“…Moreover, heavy minerals could be concentrated, but their chemical compositions have the potential to serve as indexes for provenance analysis. Many studies have revealed provenance based on the chemical compositions of heavy minerals, such as chromium spinel (Arai & Hisada, 1991;Hisada, Arai, & Lee, 1999;Hisada, Takashima, Arai, & Lee, 2008) and garnet (Takeuchi, 1994). However, the methods used in these studies are inconvenient for the following three reasons: Recently, tremendous advances have been made in quantitative elemental analysis of micro domains by using techniques such as electron probe microanalysis (EPMA), secondary ion mass spectrometry, and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) (e.g.…”