Genesis Of Skarn In Hetaoping Pb-Zn Deposit,Baoshan County,Western Yunnan Province

The Hetaoping Pb-Zn deposit of BaoShan county is located in western Yunnan province. It is one of large-scale lead-, zinc-, copper-, silver-polymetallic deposits characterized of vein skarn-type deposits ore-bearing controlled by fracture in Three River area of Yunnan province, southwestern China. There is a large number of skarn minerals in Hetaoping Pb-Zn deposit.The company has not disclosed to the contact metasomatic skarn and related magmatic rocks.It is the skarn formation ideal base for study.Other experts had studied the skarn minerals fluid inclusions,C、H、O、S、Si、Pb isotopes and skarn mineralogy to provides an indication of the skarn genesis. There is no systematic study leading to skarn space zoning, skarn mineral assemblages, skarn mineral characteristics of understanding is not complete and the overgeneralization phenomenon. It is not conducive to find out the causes of skarn. On the basis of the comprehensive geological investigation,the paper has studied the skarn basic geological characteristics, petrography, skarn mineralogy,mineral geochemistry, combined with previous results to carry out a comprehensive study. The main results show as the following:(1)The geological features about five middle skarn studies have shown that Fl fault and secondary faults control the distribution of skarns in the region, mainly percolation explain characteristics. On the deposit scale,skarn zonation is unclear; On the profile scales (<30m), skarn zonation is clear. From the center to the edge, Skarn rock Skarn rock from the center to the edge Followed by garnet skarn, tremolite garnet silicon Skarn�'garnet tremolite the epidote skarn tremolite skarn�'tremolite garnet, malachite green epidote skarn The rock�'garnet chlorite skarn rock�'mineralized marble limestone and shale bands of limestone marble.(2)Petrographic studies show it is a typical mine development calcium skarn mineral assemblages.There are mainly calcium aluminum-andradite, hedenbergite, tremolite, actinolite, epidote, chlorite. The skarn experienced dry skarn stage�'wet skarn rock stage�'quartz sulfide stage�'carbonate phase evolution.(3)Region garnet skarn can be divided into three generations. From early to late,it is followed order free ring with garnet,inside and outside the ring with the development of garnet, the outer ring with the development of garnet. Its end-member composition variations in Gro54.59And43.07～Gro1.37And94.18.No ring with garnet no apparent ring with matt abnormal homogeneous grossular end-member component content is higher. Shows a clear ring with garnet inside and outside the ring with development only in the orthogonal polarization and back-scattered color photos.The dark parts of Fe content is high.The Al content is relatively low. Outer ring with developmental garnet, its obvious outer ring with the outer ring with the exception of light, dry-color to a gray, core of full dull the edge of the ring with calcium aluminum-andradite nuclear calcium iron garnet, the dark parts the Al containing high Fe content is relatively low. Skarn pyroxene to hedenbergite stone mainly calcareous skarn typical mineral, the presence of a small amount of augite diabase dikes within the mine may have a certain impact on the skarn fluids.(4)There is correlation between LREE/HREE value of Fe3+/(Fe3++Al).It has a negative correlation with the grossular.There is a certain positive correlation between grossular content and∑REE. Adjacent areas granite is similar REE distribution patterns of type and skarn rocks garnet stone. The former total rare earth is greater than the rare earth elements in garnet. This indicates that the skarn garnet has closely relation with granite.And it may be (melting) fluid supply source of skarn in the study area.The set of granite SHRIMP U-Pb age of35.3+0.72Ma. Adjacent areas granite REE patterns with no ring with the development of the early generations of garnet distribution pattern is very similar to.They has the8Eu negative anomalies δCe abnormal.And the∑REE content compared with other types of garnet closer to granite∑REE content. More consistent distribution patterns of development inside and outside the ring with garnet granite. Garnet has δEu positive anomalies indicate that with inner and outer ring with garnet formation than the oxidizing environment. Part of the outer ring of the development of the distribution patterns of garnet granite REE patterns differ. The∑REE content is quite different, and does not have δEu,δCe abnormal. Compared with the early generations of garnet, the outer ring with garnet developmental Y/Ho ratio of carbonaceous chondritic Y/Ho ratios vary greatle.(5) The skarn closed with the a lead-zinc deposits, should be formation due to a migration of magma (molten) fluid along the fault and in the surrounding rock formation distal skarn favorable site percolation account. Fluid from magmatic rocks�'magma (molten)�'No ring with garnet�'inside and outside with developmental garnet�'outer ring development garnet�'diopside skarn and wet skarn minerals. Physical and chemical conditions generally experienced temperature550～700℃, the the a-acidic the weak oxidation-weak reducing conditions�'temperature of450to600℃, pH=of4.0～11.0Oxidation-weak oxidizing conditions�'temperature>358℃, salinity>19.21%�'temperature for wtNaClequ., pH>7, oxidizing conditions?195℃salinity8.85%wtNaClequ.,pH>7,the oxidation conditions evolution. It also further confirmed, Hetaoping lead-zinc deposits is a fluid system controlled by a deep magma (molten) distal skarn deposits, the event and the Himalayan tectonic magmatic activity.