Jurassic hornblende gabbo intrusives are distributed in Otanri, Chuncheon, and in Guwoonri, Hwacheon located in the northern part of Gyeonggi Massif. The intrusives composed mainly of amphiboles and plagioclase can be divided into two distinct rocks depending on the shape of amphiboles: (i) subspherical amphibole gabbro which has subspherical amphibole phenocryst as a major mafic phase(Sag); (ii) prismatic amphibole gabbro which has prismatic amphiboles as a principal mafic mineral(Pag). Subspherical amphiboles in Sag have higher Cr content and higher Mg($Mg+Fe^{2+}$) ratio relative to the prismatic amphiboles in Pag. This is indicative of conversion of pyroxene into amphibole with pyroxene pseudomorph. Oxygen isotopic results of plagioclase and amphibole separated from the hornblende gabbro suggest that theses minerals have experienced oxygen isotopic exchange with relatively heavy-$^{18}O$fluid for a long period, and magmatic fluid has been involved in the formation of subspherical amphiboles. Amphiboles in hornblende gabbro are composed of distinct species of pargasite, magnesiohornblende, actinolite, which formed at different stages.