The Genesis Of High-K Granites In Shuangmiao,Northern Of Hebei Province

In North China Craton,a Neoachaean ancient oceanic crust relic has been reported(Wang et al.,2012).The low Al2O3TTG rocks(2512±19Ma)in Changhanying,the Potassium granites(Closepet)with high Cr in Gelingyao,and Gabbro-monzonite rocks in Xiliang have been recognized on both sides of the relic.We used to consider that TTG rocks can be precluded as a source for the anatectic granites without certainly evidence.Now,we find more anatestic granites with similar age(2437±10 Ma),TTG rocks and grt-bear Gabbro-monzonite rocks(Sanukitoid)in Shuangmiao.The outcrop well reveals the TTG the whole process of the partial melting,which confirmed the speculation that the subduction zone may be discrimin-ated in North China Craton.The fleshy red anatectic granites(Closepet-like)with rich K and high Cr surround-ding with Huaian complex,about 15 km2 mainly exposed in eastern mountain of Shu-angmiao.Field observations show the Gradually deepened degree of partial melting.The Sanukitoid dykes intrude into weak metamorphic TTG rocks and red granites,which composed of Plagioclase,hormblende,garnet,hypersthene and biotite,and a sm-all amount of sphene and magnetite,etc.Worm structure and the collection of dark patches are found in red granites with partial melting by microscope.The potassium granite is composed of potassium feldspar,plagioclase,quartz,biotite and epidote,less garnet,uneven distribution.Chemical features:K2O/Na2O 1.15-2.24,A/CNK 1.02-1.1 1,A/NK 1.12-1.31,which belong to the rich potassium,weakly peraluminous,calc-alkaline and Ⅰ-type granites.The rare elements is characterized by high Cr,Th,Rb and low Ba,low features such as low Nb,Ta,Nb and Ta,most Eu negative anomaly.These rocks with high Cr(enriched in mantle),are rare potassium granites.The red granite with similar age(2.5Ga)in south India is considered to be related to plate subduction,called Closepet granites(Moyen and Martin,2003).Study shows that eclogite is not the source of the potassium granites by partial melting.The possible formation process is that the degree of the ancient oceanic crust subduction is so low that it is only metamorphosed to amphibolite-granulite facies,which form the low-Al2O3 TTG magma with no fully dehydrated.The breakage of the heavy relict results in Subduction interrupt.The temperature of the mantle wedge begin to rise,leading to upwelling of Sanukit-oid magma and fluid,providing the heat and complex metasomatism for the formation of red granites.