High-pressure Felsic Granulites Research Articles

Metamorphic P–T–t evolution deciphered from episodic monazite growth in granulites of the Chencai Complex and implications for the Early Paleozoic Orogeny, West Cathaysia terrane, South China

Abstract The Early Paleozoic Orogeny in eastern South China has been highly controversial. It has been alternatively interpreted to have formed in an intra-plate setting driven by far-field tectonic forces or at plate boundaries involving subduction–collision. The West Cathaysia terrane in the core of the orogen is characterized by extensive magmatism, intense deformation and especially high-grade metamorphism. Identifying early Paleozoic high-pressure (HP) metamorphism and establishing a complete P–T–t path from the high-grade metamorphic rocks could help us understand the tectono-thermal evolution process and nature of the Early Paleozoic Orogeny. Here, we present results from a felsic granulite from the Chencai Complex in the northeastern West Cathaysia terrane. Petrographic evidence, mineral compositions and phase equilibria modelling indicate that the granulite underwent a pre-peak HP stage with P–T conditions of 13.3–14.7 kbar/696–718°C and low geothermal gradients of 13–14°C km −1 , and a peak high-temperature stage with P–T conditions of 9.7–11.0 kbar/785–820°C. A clockwise P–T path involving pre-peak decompressional heating, post-peak near-isothermal decompression and near-isobaric cooling processes was constrained for the HP felsic granulite. In situ monazite U–Pb geochronology combined with previous results date these metamorphic processes at c. 440, c. 425 and c. 400 Ma, respectively. Our new metamorphic and geochronological data from the HP felsic granulite support the case that the Early Paleozoic Orogeny was a typical collisional one.

Chicheng high-pressure granulites record the paleoproterozoic tectonic evolution in the northern North China Craton

High-pressure (HP) mafic granulites are widely distributed along the Trans-North China Orogen (TNCO), and they provide important insights into the timing and tectonic processes involved in the formation of the TNCO. We discovered three types of HP granulite, including mafic, intermediate, and felsic granulites, exposed in Chicheng area, in the northern segment of the TNCO. Their mineral assemblages of prograde, peak, and post-peak metamorphic stages were identified based on petrographic investigations. SIMS U-Pb zircon analyses yielded an upper intercept age of 2547 ± 38 Ma and a lower intercept age of 1916 ± 100 Ma for one HP mafic granulite and a discordant 207Pb/206Pb age of 2479 Ma with a weighted mean 207Pb/206Pb age of 1905 ± 9 Ma for the other HP mafic granulite. For the HP intermediate granulite, an upper intercept age of 2544 ± 20 Ma was obtained. The HP felsic granulite yielded an upper intercept age of 2524 ± 23 Ma and a concordant 207Pb/206Pb age of 1906–1907 Ma. These results reveal that the protoliths of HP granulites were formed at ~ 2.5–2.55 Ga and underwent high pressure granulite facies metamorphism at ~ 1.9 Ga. The elevated Hf isotopic compositions of the metamorphic zircons from two granulite samples indicate that metamorphic fluids that have high 176Hf/ 177Hf ratios but low 176Lu/177Hf ratios were involved in their metamorphism. The low 18O isotopic features of the zircons from the intermediate granulite suggest alteration by δ18O-depleted seawater or meteoric fluids at high temperatures. By integrating geochronological data from previous studies, we infer that the formation of the TNCO may have begun as early as ~ 1.9 Ga and lasted until ~ 1.8 Ga, supporting the hypothesis that it was formed by a long-lived tectono-metamorphic event

Peridotite-derived detrital pyropes versus high-pressure felsic granulite-derived pyrope-almandine garnets from the Lower Triassic deposits of the NE foreland of the Bohemian Massif (S Poland, Central Europe)

Numerous pyrope grains (group I; Prp62–72Alm14–24Grs(<1)4–14Uv(1)2–14Sps<1–1Adr<1–2) have been found in the heavy mineral assemblages from the Older Buntsandstein arenites (Lower Triassic) cropping out in S Poland (NE foreland of the Bohemian Massif). This is the first find of the abundant detrital pyropes outside, but near to, the Bohemian Massif, and the first from the Lower Triassic deposits. In the heavy mineral assemblages from the younger wackes and marly limestones (Older Buntsandstein and Röt deposits), from the same area, Ca-low pyrope-almandines of subgroups IVA (Prp28–52Alm44–68Grs1–4Uv<1Sps1–2Adr<1) and IVB (Prp27–50Alm41–65Grs>5–15Uv<1Sps<1–2Adr<1–1) are the most numerous. The main aims of this study were to determine the primary and secondary source rocks for the garnets, and to identify a cause for the change of the garnet types in the older and younger deposits. Pyropes contained in the Bohemian Massif peridotites, presently exposed in the Moldanubian Zone, and the Kutná Hora Unit, show most comparable chemical compositions to group I pyropes. Some group I pyropes have no chemical counterparts within the comparative materials, which suggests that some other pyrope-bearing peridotites may have been exposed within the Bohemian Massif, but destroyed in the past. Garnets contained in the high-pressure felsic granulites known from several subunits of the Moldanubian Zone show similar chemical compositions to the garnets from subgroup IVA. The group I grains reveal features pointing to (possibly multiple) reworking and likely longer transport distance, while the group IV grains reveal signs of not advanced abrasion and possible short transport distance. However, no older or coeval sedimentary rocks with the similar heavy mineral assemblages, nor the garnet groups, are recognized within the Bohemian Massif or the adjacent areas, which suggests that the garnets may have been recycled from deposits largely destroyed in the past. The deposition of group IV garnets was a normal occurrence for a long time span. In contrast, the deposition of the detrital pyropes was an unusual event. These pyropes must have been redeposited from pyrope-bearing ‘horizons’ present in Carboniferous-Lower Triassic sedimentary rocks. Their availability was limited to the time span necessary for erosion of these horizons.

Petrological Investigations and Zircon U‐Pb Dating of High Pressure Felsic Granulites from the Yushugou Complex, South Tianshan, China

AbstractAs a window of insight into the lower crust, high pressure granulite has received much attention since last decade. Yushugou high pressure granulite‐peridotite Complex was located in the northeast margin of Southern Tianshan, NW China. Previous ideas agreed that the peridotite unit in Yushugou, combined with the ultramafic rocks in Tonghuashan and Liuhuangshan, represent an ophiolite belt. However, the metamorphic evolution and tectonic mechanism of the Yushugou high pressure (HP) granulite remain controversial. Petrological investigations and phase equilibrium modelling for two representative felsic granulite samples suggest two stages metamorphism of the rocks in Yushugou Complex. Granulite facies metamorphism (Stage I) with P‐T conditions of 9.8–10.4 kbar at 895–920°C was recorded by the porphyroblastic garnet core; HP granulite facies metamorphism (Stage II) shows P‐T conditions of 13.2–13.5 kbar at 845–860°C, based on the increasing grossular and decreasing pyrope contents of garnet rims. The Yushugou HP felsic granulites have recorded an anticlockwise P‐T path, characterized by the temperature decreasing and pressure increasing simultaneously. The LA‐ICP‐MS isotopic investigations on zircons from the felsic granulite show that the protolith ages of the granlulites are ∼430 Ma, with two age groups of ∼390 Ma and 340–350 Ma from the metamorphic rims of zircon, indicating the Stage I and II metamorphic events, respectively. A tectonic model was proposed to interpret the processes. The investigated felsic granulite was derived from deep rooted hanging wall, with Stage I granulite facies metamorphism of ∼390 Ma, which may be related to the Devonian arc magmatic intrusion; Stage II HP granulite facies metamorphism (340–350 Ma) may due to the involvement of being captured into the subducting slab and experienced the high pressure metamorphism.

Computational study of deformation mechanisms and grain size evolution in granulites – Implications for the rheology of the lower crust

Most of granulite terrains worldwide are characterized by large mean grain sizes of 1 mm or more. An important exception are the high-pressure felsic granulites in the Bohemian Massif, the European Variscan belt. There, recrystallization of original coarse-grained ternary feldspar led to formation of a fine-grained (∼100 μm) mixed matrix dominated by plagioclase and K-feldspar. This change occurred at temperatures of ∼850 °C and was probably caused by chemically induced decomposition related to slight cooling and enhanced by deformation during continental collision. The resulting microstructure shows indications of diffusion creep assisted by melt-enhanced grain-boundary sliding. Further on, minor coarsening occurred associated with deformation by dislocation creep and aggregation of mineral phases. Using a thermodynamics-based model of grain size evolution we show that stability of the fine-grained microstructure crucially depends on Zener pinning in the two-phase mineral matrix. Pinning efficiently hinders grain growth, and the small grain size that resulted from the ternary feldspar decomposition can be stable even at high temperatures. The late switch from the grain-size-sensitive creep to dislocation creep is rather difficult to explain by temperature and strain rate (or stress) changes only. However, a simple incorporation of melt solidification can successfully simulate this behavior. Alternatively, the switch and the associated grain size growth can be related to mineral phase aggregation at lower pressure–temperature conditions resulting into a decrease of pinning efficiency. This study suggests that the fine grain size of the Bohemian granulites, in contrast to the common coarse-grained type, stems from abrupt recrystallization during the high-pressure high-temperature conditions, and pinning in the fine-grained matrix. Such a process may in some cases significantly and suddenly reduce the strength of the lower continental crust and allow for its efficient redistribution.

Interface coupled dissolution-reprecipitation in garnet from subducted granulites and ultrahigh-pressure rocks revealed by phosphorous, sodium, and titanium zonation

Garnet zonation provides an unparalleled record of the pressure-temperature-time-fluid evolution of metamorphic rocks. At extreme temperature conditions >900 °C, however, most elements preserve little zonation due to intracrystalline diffusional relaxation. Under these conditions, slowly diffusing trace elements including P, Na, and Ti have the best chance of recording metamorphic histories. Here we map dramatic zoning patterns of these elements in subducted high-pressure felsic granulite (Saxon Granulite Massif) and ultrahigh-pressure diamondiferous “saidenbachite” (Saxonian Erzgebirge, Bohemian Massif). The results show that garnet replacement via interface coupled dissolution-reprecipitation can strongly affect garnet compositions in subduction zones and that P, Na, and Ti record burial and exhumation histories that are otherwise lost to diffusion. In these samples, P diffuses the slowest, and Ti the fastest.

Importance of crustal relamination in origin of the orogenic mantle peridotite–high-pressure granulite association: example from the Náměšť Granulite Massif (Bohemian Massif, Czech Republic)

A characteristic association of crustal and mantle rocks is commonly used to decipher processes at the mantle–crust interface of HP–UHP collisional orogenic systems. Also, in the Variscan orogenic root of the Bohemian Massif (the Moldanubian Zone), high-pressure felsic granulites are often accompanied by spinel or garnet peridotites. This association was investigated using petrography, zircon geochronology and whole-rock geochemical data from the Náměšť Granulite Massif. The geochemical signature of the granulite is the same as for other Moldanubian occurrences, suggesting nearly isochemically metamorphosed felsic metaigneous rocks of Saxothuringian provenance. SHRIMP zircon dating yielded two main age maxima, at 395.2 ± 4.4 and 337.2 ± 1.7 Ma, reflecting an Early Devonian protolith and Visean HP metamorphism. As shown by Sr–Nd isotopic data, the variably refertilized harzburgite or depleted lherzolite was variously contaminated by mature crustal material resembling the studied granulites. To account for the origin of these HT–HP rock associations we suggest a new geotectonic model. An eastward continental subduction of Early Palaeozoic felsic metaigneous material of Saxothuringian origin was followed by its relamination at the bottom of the autochthonous lower crust. Ascending felsic granulites derived from the relaminated lower plate material sampled refertilized harzburgites originally formed in a back-arc. The complete assemblage was subsequently exhumed, forming large, diapir-like bodies. Supplementary material: Sample coordinates from the Náměšť Granulite Massif, analytical techniques, SHRIMP age measurements on zircon grains and whole-rock geochemical data are available at http://www.geolsoc.org.uk/SUP18833 .

Origin of Early Paleozoic garnet peridotite and associated garnet pyroxenite in the south Altyn Tagh, NW China: Constraints from geochemistry, SHRIMP U–Pb zircon dating and Hf isotopes

Garnet peridotite, garnet pyroxenite, mafic granulite and dominant felsic granulite constitute a high-pressure/high-temperature (HP/HT) metamorphic terrane in the south Altyn Tagh, North Tibet (China). Garnet peridotite and associated garnet pyroxenite occur as slices or lenses within high pressure felsic granulite. Previous studies indicate that garnet peridotite experienced the peak HP/HT metamorphism, followed by a medium pressure granulite-facies overprint. However, the origin of the garnet peridotite and associated garnet pyroxenite remains controversial. In this contribution, we present new zircon U–Pb and Hf isotopic data and whole-rock major, trace element and Sr–Nd isotopic data for the representative garnet peridotites and associated garnet pyroxenites. SHRIMP U–Pb dating on the inherited (magmatic) zircons from the garnet peridotites gave an U–Pb age of ca. 780Ma, which is interpreted as the age of the ultramafic magma crystallization. The metamorphic zircons yield an age of ca. 500Ma, which is consistent with the Sm–Nd isochron age of 493±24Ma for whole rock, garnet and clinoproxene from a garnet pyroxenite, representing the timing of peak metamorphism. The Baishiwake garnet peridotites and garnet pyroxenites show relatively high contents in Fe2O3, TiO2, P2O5, Nb, Zr, and Y, but significantly low MgO, Cr, A12O3 and Ni contents. They possess enriched LREE, nearly flat HREE, slightly positive Eu anomaly and weak negative anomalies in Nb and Ti. The relatively high 87Sr/86Sr ratios (0.707–0.710) and low 143Nd/144Nd ratios (0.5123–0.5124) imply a possible crust contamination prior to HP metamorphism. Integrating these data together with previous studies, we suggest that the Bashiwake garnet peridotites and associated garnet pyroxenites were derived from mantle-derived magmas which intruded into the continental crust during the Neoproterozoic and then experienced a common HP/HT metamorphism with felsic crustal rocks in the Early Paleozoic (ca. 500Ma).

Intracrystalline microstructures in alkali feldspars from fluid-deficient felsic granulites: a mineral chemical and TEM study

Samples of essentially “dry” high-pressure felsic granulites from the Bohemian Massif (Variscan belt of Central Europe) contain up to 2-mm-large perthitic alkali feldspars with several generations of plagioclase precipitates in an orthoclase-rich host. The first generation takes the form of lenses homogeneous in size, whereas the size of a second generation of very thin albite-rich precipitates is more variable with comparatively high aspect ratios. In the vicinity of large kyanite, garnet or quartz inclusions, the first generation of plagioclase precipitates is significantly less abundant, the microstructure is coarser than in the remainder of the perthitic grain and the host is a tweed orthoclase. The first generation of precipitates formed at around 850 °C during the high-pressure stage (16–18 kbar) of metamorphism. Primary exsolution was followed by primary coarsening of the plagioclase precipitates, which still took place at high temperatures (850–700 °C). The coarsening was pronounced due to the access of fluids in the outer portions of the perthitic alkali feldspar and in more internal regions around large inclusions. The second generation of albite-rich precipitates was formed at around 570 °C. TEM investigations revealed that the interfaces between the second-generation plagioclase lamellae and the orthoclase-rich host are coherent or semi-coherent. During late evolutionary stages of the perthite, albite linings were formed at phase boundaries, and the perthitic microstructure was partially replaced by irregularly shaped precipitates of pure albite with incoherent interfaces. The albitization occurred below 400 °C and was linked to fluid infiltration in the course of deuteric alteration. Based on size-distribution analysis, it is inferred that the precipitates of the first generation were most probably formed by spinodal decomposition, whereas the precipitates of the second generation rather were formed by nucleation and growth.

Growth of plagioclase rims around metastable kyanite during decompression of high-pressure felsic granulites (Bohemian Massif)

Samples of high-pressure felsic granulites from the Bohemian Massif (Variscan belt of Central Europe) characterized by a peak metamorphic (high-pressure) mineral assemblage of garnet-kyanite-plagio- clase-K-feldspar-quartz ± biotite show well-developed plagioclase reaction rims around kyanite grains in two microstructural settings. In one setting, kyanite is randomly distributed in the polyphase matrix, whereas in the other setting, it is enclosed within large perthitic K-feldspar. Kyanite is regarded as a relict of the high-pressure metamorphic assemblage that became metastable during transition to a low- pressure overprint. Plagioclase rims from both microstructural settings show continuous outwards decrease of the anorthite content from An32-25 at the contact with kyanite to An20-19 at the contact with the matrix or to the perthitic K-feldspar respectively. Based on mass balance considerations, it is shown that in some cases, a small amount of kyanite was consumed in the rim-forming reaction to provide the Al2O3 component for the growth of plagioclase, whereas in other cases no Al2O3 from kyanite was necessary. In a majority of examples, the necessary Al2O3 was supplied with CaO and Na2O from the surrounding matrix material. For kyanite in perthite, a thermodynamic analysis reveals that the kyanite became metastable at the interface with the host perthite at the peak metamorphic pressure, and therefore the plagioclase rim started to grow at � 18 kbar. In contrast, kyanite in the polyphase matrix remained stable down to pressures of � 16 kbar, and the plagioclase rim only started to grow at a later stage during the decompression. Plagioclase rims around kyanite inclusions within large perthite have a radial thickness of up to 50 lm. In contrast, the radial thickness of plagioclase rims around kyanite in the polycrystalline matrix is significantly larger, up to 200 lm. Another peculiarity is that the plagioclase rims around kyanite in the matrix are polycrystalline, whereas the plagioclase rims around kyanite inclusions in perthitic hosts are single crystals with the same crystallographic orientation as the host perthite. The difference in rim thickness for the two microstructural settings is ascribed to the differences in the efficiency of chemical mass transfer next to the reaction site. The comparatively large thickness of the plagioclase rims grown around kyanite in the matrix is probably due to efficient material transport along the grain and phase boundaries in the matrix. In contrast, chemical mass transfer was comparatively slow in the large perthitic K-feldspar grains.

Primary magnetic fabric in an ultramafic body (Moldanubian Zone, European Variscides) survives exhumation-related granulite-amphibolite facies metamorphism

Serpentinized peridotite–clinopyroxenite, approximately 11 × 5 m in size, enclosed in high-pressure felsic granulite, occurs in a quarry near the village of Bory (Gföhl Unit of the Moldanubian Zone of Western Moravia, Czech Republic). The anisotropy of magnetic susceptibility (AMS) was used to investigate the fabrics of both the ultramafic body and the host granulite. The granulite shows a PT path from above 2 GPa/850–900 °C following nearly isothermal decompression to sillimanite stability field with subsequent cooling. Two foliations (S 1-preserved only in isoclinal folds and the dominant S 2 foliation parallel to leucocratic bands) are visible in granulite. Through investigating low-field variation of the AMS, one could resolve the AMS into the field-independent and field-dependent components. In the ultramafic body, the former component is due to mafic silicates and pure magnetite, while in the host granulite it is due to mafic silicates. The latter component is due to pyrrhotite in both the ultramafic body and granulite. The field-independent and field-dependent components are coaxial within ultramafic body and within granulite, but show different orientations between the ultramafic body and granulite. Consequently, the magnetic fabric in the ultramafic body is different from that in the host granulite even though they experienced common structural history during granulite facies metamorphism. The componental movements forming the granulite fabric were evidently not strong enough to strongly overprint the magnetic fabric of ultramafic rocks. The ultramafic rocks have therefore sufficient mechanical strength to maintain their pre-granulite facies metamorphic fabric even at such high temperatures and high pressure that are characteristic of granulite facies metamorphism.

Magnetic fabric relationship between an ultrabasic body and host high-pressure felsic granulite (Moldanubian Zone, European Variscides): the effect of exhumationrelated granulite-amphibolite facies metamorphism

Magnetic fabric relationship between an ultrabasic body and host high-pressure felsic granulite (Moldanubian Zone, European Variscides): the effect of exhumationrelated granulite-amphibolite facies metamorphism

History of Zircon Growth in a High-Pressure Granulite within the Eastern Himalayan Syntaxis, and Tectonic Implications

High-pressure (HP) granulites exposed within the eastern Himalayan syntaxis are dominantly felsic rocks. They were displaced southward over the Pei sequence by the NW-dipping Upper Thrust. Twenty-three SHRIMP U/Pb analyses of zircons from one HP sample demonstrate that this rock was derived from Proterozoic sedimentary rocks that underwent high-temperature metamorphism or partial melting to form granitoids or paragneisses at about 500 Ma. During Oligocene collision between India and Asia, these crystalline rocks were buried beneath south Tibet, recrystallizing to form HP felsic granulites at 30-33 Ma, with a metamorphic retrogression at about 23 Ma. Evidently the south Tibetan crust was thickened, and then uplifted at this time.

Diffusion-controlled development of silica-undersaturated domains in felsic granulites of the Bohemian Massif (Variscan belt of Central Europe)

Plagioclase rims around metastable kyanite crystals appear during decompression of high-pressure felsic granulites from the high-grade internal zone of the Bohemian Massif (Variscan belt of Central Europe). The development of the plagioclase corona is a manifestation of diffusion-driven transfer of CaO and Na2O from the surrounding matrix and results in isolation of kyanite grains from the quartz- and K-feldspar-bearing matrix. This process establishes Si-undersaturated conditions along the plagioclase- kyanite interface, which allow crystallization of spinel during low-pressure metamorphism. The process of the plagioclase rim development is modeled thermody- namically assuming local equilibrium. The results combined with textural observations enable estimation of equilibration volume and diffusion length for Na and Ca that extends ~400-450 and ~450-550 lm, respectively, around each kyanite crystal. Low esti- mated bulk diffusion coefficients suggest that the diffusion rate of Ca and Na is controlled by low diffusivity of Al across the plagioclase rim.

Geochronological constraints on the evolution of high-pressure felsic granulites from an integrated electron microprobe and ID-TIMS geochemical study

A combined geochronological, geochemical, and Nd isotopic study of felsic high-pressure granulites from the Snowbird Tectonic Zone, northern Saskatchewan, Canada, has been carried out through the application of integrated electron microprobe and isotope dilution thermal ionization mass spectrometry (ID-TIMS) techniques. The terrane investigated is a 400 km 2 domain of garnet–kyanite–K–feldspar-bearing quartzofeldspathic gneisses. Monazite in these granulites preserves a complex growth history from 2.6 to 1.9 Ga, with well-armored, high Y and Th grains included in garnet yielding the oldest U–Pb dates at 2.62 to 2.59 Ga. In contrast, matrix grains and inclusions in garnet rims that are not well-armored are depleted in Y and Th, and display more complicated U–Pb systematics with multiple age domains ranging from 2.5 to 2.0 Ga. 1.9 Ga monazite occurs exclusively as matrix grains. Zircon is typically younger (2.58 to 2.55 Ga) than the oldest monazite. Sm–Nd isotope analysis of single monazite grains and whole rock samples indicate that inclusions of Archean monazite in garnet are similar in isotopic composition to the whole rock signature with a limited range of slightly negative initial ɛ Nd. In contrast, grains that contain a Paleoproterozoic component show more positive initial ɛ Nd, most simply interpreted as reflecting derivation from a source involving consumption of garnet and general depletion of HREE's. Our preferred interpretation is that the oldest monazite dates record igneous crystallization of the protolith. The ca. 2.55 Ga dates in zircon and monazite record an extensive melting event during which garnet and ternary feldspar formed. Very high-pressure (> 1.5 GPa) metamorphism during the Paleoproterozoic at 1.9 Ga produced kyanite from garnet breakdown, and resulted in limited growth of new monazite and zircon. In the case of monazite, this is likely due to the armoring and sequestration of early-formed monazite such that it could not participate in metamorphic reactions during the high-pressure event, as well as the depletion of the REE's due to melt loss following the early melting event.

Sapphirine-bearing high pressure mafic granulite and its implications in the south Altyn Tagh

Sapphirine-bearing high pressure mafic granulites are recognized in the Bashiwake area of the south Altyn Tagh. Mafic granulites and associated peridotites occur as lenses within kyanite-bearing high pressure felsic granulites. Sapphirine occurs as intergrowths with corundum, spinel and Ca-rich plagioclase in symplectite in between garnet and clinopyroxene. Reaction textures and mineral compositions indicate that sapphirine-bearing symplectites formed by reactions consuming kyanite, garnet and clinopyroxene. Therefore, both petrographic observations and the mineral compositions suggest that these quartz-free mafic granulites had an eclogite origin with an assemblage of garnet + clinopyroxene + kyanite, which is estimated to be stable atT = 1000 °C andP ⩾ 2.1 GPa. The sapphirine-bearing symplectites are resulted from isothermal decompression or decompression with slight cooling during exhumation of the host rock.

Study and implication of the high-pressure felsic granulite in the Qinling complex of East Qinling

There is a typical assemblage of garnet + kyanite + microperthite + quartz + rutile in high-pressure (HP) felsic granulite of Qinling complex in Songshugou area. East Qinling. The HP granulite was formed at 800 -900℃ and 1.3 -1.6GPa and has experienced two stages of retrograde metamorphism at 600- 650 ℃, 0.8-1.0GPa and 500-600℃, 0.3-0.6GPa, forming two retrograde metamorphic assemblages of margarite + plagiodase (PlI)+quartz and sillimanite + biotite + plagioclase(PlII) + microdine+quartz, respectively. They construct a two-stage clockwise P-T path which shows down-pressure cooling in both early and late stage.