Mesozoic　porphyritic　rocks　from　the　Zijinshan　area,　southwestern　Fujian　Province,　China,　are　andesitic　to　rhyolitic　in　composition.　The　whole-rock　SiO2　contents　of　these　rocks　are　between　62.5%　and　78.1%.　Magmatic　zircon　from　the　Mesozoic　porphyritic　rocks　was　determined　via　secondary-ionization　mass　spectrometry　(SIMS)　for　the　U-Pb　age　and　Hf　and　O　isotopes.　The　zircon　U-Pb　ages　could　be　mainly　divided　into　three　age　groups:　Group　1:　similar　to　138.8　Ma;　Group　2:　109.2　similar　to　107.4　Ma;　and　Group　3:　99.7　similar　to　98.2　Ma.　The　epsilon　Hf(t)　and　delta　O-18　values　of　the　porphyritic　zircons　showed　that　the　porphyritic　rocks　in　Group　2　were　more　affected　by　mantle-derived　magma.　Combined　with　previous　research　results,　the　medium-acidic　magmatism　in　the　southwestern　Fujian　Province　can　be　divided　into　eight　periods:　Paleoproterozoic,　Mesoproterozoic,　Middle　Neoproterozoic,　Silurian　to　Lower　Devonian,　Permian　to　Triassic,　Middle　Jurassic　to　early　Lower　Cretaceous,　late　Lower　Cretaceous,　and　late　Lower　Cretaceous　to　early　Upper　Cretaceous.　The　Paleoproterozoic　crust　was　the　predominant　magmatic　source　for　the　subsequent　Mesoproterozoic　to　Jurassic　magmatism,　but　the　only　melts　that　were　closely　related　to　mineralization　were　derived　from　partial　melting　of　the　Mesoproterozoic　crust　and　a　more　depleted　upper　mantle.