Abstract: The poly-phenocryst plagioporphyry in Tanling, Wu'an (Hebei) was found with poly-phenocryst porphyrotopic texture and microcrystalline matrix. The rim of plagioclase phenocrysts consists of variable-width perthite, while oligoclase-albite made up the broad core where trace of amphibole and biotite were found in isolated phenocrysts. The matrix comprises 11 minerals mainly: winchite, perthite (An0Ab8.4Or91.5An0.1Ab57.3Or42.6), quartz, potassium feldspar (An0.3Ab5.9Or93.7An0.3Ab4.7Or95.2), albite(An0.2Ab98.3Or1.5An0.1Ab99.2Or0.7), magnetite, hematite, ilmenite, apatite, sphene, and zircon. T-P calculation of amphiboles using amphibole barometer showed that the average crystal pressure decreased from 34.05 to 24.32 MPa, corresponding temperature dropped from 660.35 to 598.49 ℃, and crystal depth changed from 1.29 to 0.93 km in the matrix amphibole core. In contrast, crystal pressure (159.51178.19 MPa), temperature (817.68819.79 ℃) and depth (6.036.73 km) were all higher in the plagioclase phenocryst amphiboles. Al2O3-TiO2 diagram showed that the plagioclase phenocryst amphibole and biotite in plagioclase phenocryst was crust-mantle mixed origin, and the matrix amphibole was crust origin. LA-ICP-MS analysis of matrix minerals revealed that Al2O3-TiO2 most of them were enriched in LILE and depleted in LREE, indicating fluid was involved during the formation of matrix minerals. ICT scannogram demonstrated that pore and iron oxides volume in the matix was about 3.428% and 4.371% respectively, and they each had weak-connectivity. Above all, we suggest that: (1) A large amount of plagioclase phenocrysts ascended rapidly to near surface with no sign of corrosion or resorption, suggesting the remobilizing mechanism of frozen magma chambers is closely related to fluid; (2) the matrix magma of plagioporphyry was probably a melt-fluid flow rich in Fe, K, P, Si, Na, etc., and (3) the plagioporphyry in Tanling, Wu'an may provide physical boundary conditions for migration or unloading of ore-forming material as well as clues for deep prospecting.

Key words: Poly-phenocryst plagioporphy, amphibole, geothermobarometer, remobilizing mechanism of frozen magma chambers