Petrology, geochronology and tectonic implications of Mesozoic high Ba–Sr granites in the Haemi area, Hongseong Belt, South Korea

Abstract

Collision between the North and South China continental blocks began in the Korean peninsula during the Permian (290-260 Ma). The Haemi area in the Hongseong collision belt (proposed as the eastern extension in South Korea of the Dabie-Sulu collision zone of China) within the Gyeonggi Massif comprises post-collisional high Ba-Sr granite with intermediate enclaves that intruded into the Precambrian rocks. The intermediate enclaves have a shoshonitic affinity whereas the granite is a high-K calc-alkaline variety.The chondrite-normalized rare earth element (REE) pattern with relative enrichment of LREE over HREE and absence of a significant negative Eu anomaly typifies both enclaves and granite. Geochemical similarities of enclaves and granite are attributed to the involvement of enriched mantle sources in their genesis. However, dominant crustal components were involved in the formation of high Ba-Sr granites. A granite crystallization age of 233 Ϯ 2 Ma was obtained from SHRIMP U-Pb zircon dating. This age is slightly younger than the Triassic collision event in the Hongseong Belt. Geochemical data, U-Pb zircon age, and regional tectonics indicate that the Haemi high Ba-Sr granite formed in a postcollisional tectonic environment. A Mesozoic post-collisional lithospheric delamination model can account for the genesis of high Ba-Sr granite in the Haemi area.

Late Neoarchean potassic high Ba–Sr granites in the Taishan granite–greenstone terrane: Petrogenesis and implications for continental crustal evolution

“…However, it is evident that the lower Mg number and P 2 O 5 contents and higher K 2 O/Na 2 O ratios of all potassic granites in this study are comparable to typical Phanerozoic high Ba-Sr granites ( Fig. 10a-c; Tarney and Jones, 1994;Fowler et al, 2001;Moyen et al, 2001Moyen et al, , 2003Qian et al, 2003;Fowler et al, 2008;Ye et al, 2008;Choi et al, 2009), and are distinct from Archean sanukitoids and the Closepet-type granites (e.g., Smithies and Champion, 2000;Halla, 2005;Kovalenko et al, 2005;de Oliveira et al, 2009;Martin et al, 2009;de Oliveira et al, 2010). They are also distinguishable from the late Archean sanukitoids and adakitic intrusions in the study area (see Fig.…”

“…The Closepet-type granite is from Moyen et al (2001Moyen et al ( , 2003. High Ba-Sr granites are from Fowler et al (2001Fowler et al ( , 2008, Qian et al (2003), Ye et al (2008) and Choi et al (2009). Fig.…”

“…For example, Tarney and Jones (1994) proposed that they were probably derived by (1) the partial melting of subducted ocean islands or ocean plateaus, (2) the partial melting of underplated mafic rocks, or (3) the partial melting of veined lithospheric mantle that had been metasomatized by asthenosphere-derived carbonatitic melts; in addition, some authors interpreted them as the products of partial fusion of the mafic lower crust (e.g., Ye et al, 2008;Choi et al, 2009), whereas other workers invoked an origin of enriched subcontinental lithospheric mantle to account for their genesis (e.g., Fowler and Henney, 1996;Fowler et al, 2001;Qian et al, 2003;Fowler et al, 2008). Alternatively, taking into account their similar geochemical signatures to sanukitoids and TTGs, such as high Ba-Sr contents, Sr/Y and (La/Yb) cn ratios and strongly fractionated REE patterns, and close space-time distribution with the latter, the petrogenesis of high Ba-Sr granites may be related to these rocks or their fractionation products (Smithies et al, 2004;Fowler et al, 2008).…”

“…There is a consensus that high Ba-Sr granites are generally emplaced in extensional or non-compressional tectonic settings, such as during lithospheric extension, slab breakoff, or late-to post-orogenic gravitational collapse following an episode of crustal thickening (e.g., Qian et al, 2003;Fowler et al, 2008;Ye et al, 2008;Choi et al, 2009). These events may follow a period of subduction.…”

Petrology of the Syenites in Sancheong, Korea

“…또한 오대산 인근 지역에서도 대륙충돌 후 환 경(post collision tectonic setting)에서 형성된 맨거라 이트(mangerite)와 초고온 변성작용이 알려졌으며 (Oh et al, 2006a;2006b;Kim et al, 2011), 경기육괴 여러 지역에서도 보고된 바 있다. 이를 정리하면 경 기육괴 서부에 위치한 남양 지역에서 227 Ma의 화강 암 (Sagong et al, 2005), 홍성 지역에서 233 Ma의 해미 화강암 (Choi et al, 2008)과 232 Ma의 맨거라 이트 및 230 Ma의 섬장암 , 경기육 괴 중부에 위치한 양평 지역에서 227~231 Ma의 섬 장암과 반려암 (Williams et al, 2009;Lee and Oh, 2010), 춘천 후동리 지역에서 228 Ma 섬록암 (Park, 2009), 강원도 양양지역에서 231 Ma의 섬장암 (Oh, 2014)이다. 이와 같이 북중국판과 남중국판 충돌 후 화성활동에 의해 형성된 것으로 판단되는 트라이아스 기의 쇼쇼나이트(shoshonite)의 특성을 갖는 암석들이 최근 학계에서 새롭게 주목받고 있다 (Park et al, 2011;Oh, 2014).…”