• Title/Summary/Keyword: Mangerite

Search Result 2, Processing Time 0.015 seconds

The Characteristic of Mangerite and Gabbro in the Odaesan Area and its Meaning to the Triassic Tectonics of Korean Peninsula (오대산 지역에 나타나는 맨거라이트와 반려암의 특징과 트라이아스기 한반도 지체구조 해석에 대한 의미)

  • Kim, Tae-Sung;Oh, Chang-Whan;Kim, Jeong-Min
    • The Journal of the Petrological Society of Korea
    • /
    • v.20 no.2
    • /
    • pp.77-98
    • /
    • 2011
  • The igneous complex consisting of mangerite and gabbro in the Odaesan area, the eastem part of the Gyeonggi Massif, South Korea, intruded early Paleo-proterozoic migmatitic gneiss. The mangerite is composed of orthopyroxene, clinopyroxene, amphibole, biotite, plagioclase, pethitic K-feldspar, quartz. The gabbro has similar mineral assemblage but gabbro has minor amounts of amphibole and no perthitic K-feldspar. The gabbro occurs as enclave and irregular shaped body within the mangerite, and the boundary between the mangerite and gabbro is irregular. Leucocratic lenses with perthitic K-feldspar are included in the gabbro enclaves. These textures represent mixing of two different magmas in liquid state. SHRIMP U-Pb zircon age dating gave $234{\pm}1.2$ Ma and $231{\pm}1.3$ Ma for mangerite and gabbro, respectively. These ages are similar with the intrusion ages of post collision granitoids in the Hongseong (226~233 Ma) and Yangpyeong (227~231 Ma) areas in the Gyeonggi Massif. The mangerite and gabbro are high Ba-Sr granites, shoshonitic and formed in post collision tectonic setting. These rocks also show the characters of subduction-related igneous rock such as enrichment in LREE, LILE and negative Nb-Ta-P-Ti anomalies. These data represent that the mangerite and gabbro formed in the post collision tectonic setting by the partial melting of an enriched lithospheric mantle during subduction which occurred before collision. The heat for the partial melting was supplied by asthenospheric upwelling through the gab between continental and oceanic slabs formed by slab break-off after continental collision. The distribution of post-collisional igneous rocks (ca. 230 Ma) in the Gyeonggi Massif including Odaesan mangerite and gabbro strongly suggests that the tectonic boundary between the North and South China blocks in Korean peninsula passes the Hongseong area and futher exteneds into the area between the Yangpyeong-Odaesan line and Ogcheon metamorphic belt.

Petrology of the Syenites in Hapcheon, Korea (경남 합천 지역의 섬장암에 관한 암석학적 연구)

  • Ok, Eun-Young;Kim, Jong-Sun;Lee, Sang-Won
    • The Journal of the Petrological Society of Korea
    • /
    • v.26 no.1
    • /
    • pp.13-43
    • /
    • 2017
  • In the Hapcheon area, hypersthene-bearing monzonite (mangerite) and syenite are recognized. The main minerals of syenite are alkali feldspar, plagioclase, amphibole, biotite, and quartz. Anhedral hornblende and biotite are interstitial between feldspar and quartz, indicating that the hydrous minerals were crystallized later on. Based on petrochemical studies of major elements, syenite is alkaline series, metaluminous, and I-type. The variation patterns in the trace and rare earth elements of mangerite and syenite show the features of subduction-related igneous rock such as depletion of HFSE, relative enrichment in LILE to LREE, and negative Nb-P-Ti anomalies. Based on the experimental data and petrographic characteristics of the syenite, Hapcheon syenitic magma is considered to be formed by partial melting in a dry system. SHRIMP U-Pb zircon data yield the Triassic age as $227.4{\pm}1.4Ma$ in mangerite, $215.3{\pm}1.2Ma$ in syenite, and $217.9{\pm}2.6Ma$ in coarse-grained syenite, respectively. The mangerite age is similar to those of post-collisional plutonic rocks in Hongseong (226~233 Ma), Yangpyeong (227~231 Ma), and Odaesan (231~234 Ma) areas in the Gyeonggi Massif. Syenites were intruded after about 10 Ma. The features seen in the mangereite and syenite rocks can be explained by models such as the continental collision and slab break-off and the lithosphere thinning and asthenosphere upwelling model.