Study On Metallogenic Regularity Of Mesozoic Precious And Non-ferrous Deposits In Jiaodong Peninsula

Jiaodong area is located in the connected zone of the Paleo-Tethys and the Pacific-rim tectonicdomain, across the North China Plate and the Sulu-Dabie orogenic belt. Mesozoic tectonic andmagmatism activities are frequent, especially in early Yanshanian when it changed from passivecontinental margin into active margin. Since the region entered into Pacific-rim tectonic domain, therewas a strong crust-mantle interaction, mantle fluid invasion and significantly diagenesis-mineralization.This paper took the latest deposit theory as a guide, the geodynamic evolution as the main line, themodern analytical techniques as the assistance, combining the field investigation with the laboratoryanalysis test, to further explore and re-determine the dynamical evolution of the diagenesis andmineralization in Jiaodong area in the Mesozoic period, based on comprehensive analysis ofmetallogenic conditions and previous researches. It studied in-depth on the metallogenic conditions andmineralization ages of various typical deposits, determined the genetic types, set up the correspondingmetallogenic models and summarized the spatial and temporal distribution of the deposits. And throughthe comparative study, the Mesozoic precious and non-ferrous deposits in Jiaodong area were dividedinto2mineralization series controlled by dynamics mechanism in different stages of tectonic evolution,including5metallogenic sub-series and15deposit–types.It’s clearly pointed out that the mineralization of rare beryllium was mainly associated with thecollision of Yangtze and North China plate in the late Indo-Chinese epoch, while the diagenesis andmineralization in the area, since the Mesozoic Yanshanian was strictly controlled by the subduction ofthe Izanaqi plate. Five major diagenesis and mineralization activities occurred in Yanshanian,corresponding to three expansion peaks of the ancient Pacific plate (156.6Ma,137Ma and97Ma) andintermediate terms. It pointed out that in early Yanshanian (160~155Ma), eastern Eurasia transformedfrom passive to active continental margin, Izanaqi plate started subduction to Eurasian plate, formingthe Xingjiashan porphyry-skarn type molybdenum-tungsten deposit. In late Yanshanian (135~125Ma),the constant subduction of Izanaqi plate and the continuous thickening of the lithosphere led tolarge-scale lithospheric delamination and the formation of Xiangkuang porphyry-skarn typeCu-(Mo)-Pb-Zn deposit and Wangjiazhuang epithermal vein-type copper-zinc deposit. During125~115Ma, NWW fast subduction of cold Izanaqi oceanic crust triggered intense convective and violentthinning of mantle lithosphere, the influx of mantle-derived C-H-O fluid led to the accumulation ofmassive gold in the crust, forming Jiaojia, Linglong, Panma and Chakuang style orogenic gold depositsetc. and epithermal gold deposits in the edge of Jiaolai Basin. During115~110Ma, Izanaqi plate retreatsubducted, Jiaodong region changed into continental arc environment, the crust-mantle mixing magmaintruded, controlling the formation of Lengjia, Shangjiazhuang, Nantai and other porphyrycopper-molybdenum polymetallic deposits; During100~90Ma, with subduction demise of theIzanaqi-Pacific mid-ocean ridge, the strong convective of the upper mantle led to strong extension of the lithosphere, forming Tangcundianzi medium-low temperature hydrothermal type gold-lead-zinc-silver-copper polymetallic deposit and Dujiaya Carlin-type-like gold deposit.LA-ICP-MS and Re-Os dating have been applied for host-rocks and molybdenite datingrespectively of Xingjiashan molybdenum-tungsten deposit, the results show the age of Xingfushan rockis (157±2) Ma, while the formation age of molybdenum is (158.7±2.5) Ma. Thus, the Xingjiashanmolybdenum-tungsten deposit formed in early Yanshanian. The paper proposes and demonstrates theexistence of molybdenum and tungsten polymetallic mineralization in Jiaodong, early Yanshanian ofMesozoic, by contrasting with copper molybdenum polymetallic mineralization in eastern China at thistime; and pointed out that this mineralization in Jiaodong should occur during the160~155Ma, fillingthe gaps in study of mineralization during this period.The systematic studies on mineralization background, geological characteristics, mineralizationages and genesis of the Dujiaya gold deposit of Fushan area, molybdenum-copper deposits inWeideshan area and Datuanliujia beryllium deposit of Rongcheng city, etc. have been carried outrespectively. For the first time, it’s clearly stated Dujiaya gold deposit is Carlin type (-like),Lengjia-Nantai copper-molybdenum deposits in Weideshan area are porphyry type, Datuanliujiaberyllium deposit is meso-epithermal type, and established the corresponding metallogenic model. Theage of host-rock of porphyry copper-molybdenum deposit in Weideshan area is between (113.4±1.8) Maand (114.2±2.1) Ma, indicating that the mineralization should occur at115~110Ma. Study of theCarlin-type (-like) gold deposit provided strong evidence of the existence of lithospheric extension, andfilled the gaps in researches on the deposits during this period. Also, it pointed out that the goldmineralization in Fenzishan group in Gaotuan-Dongting of Fushan area, south-central part ofQixia-Penglai-Fushan region may be similar to this type, Dujiaya gold deposit and Longkou golddeposit (micro-disseminated type) found in the area are located at the south and north boundariesrespectively.It analyzed comprehensively on the background and metallogenic conditions of Jiaojia, Linglong,Panma and Chakuang type orogenic gold deposits, and pointed out that the first three deposits werecontrolled by the gentle faults due to middle crust discontinuities faces in the western region ofJiaodong area, occurred because of the lithosphere delamination, crustal stress relaxation but still insqueezed state. Mantle C-H-O fluids provided the main ore-forming fluids and minerals. Mineralizationoccurred in the medium depth of6.32~9.35km, with the fluids of moderate-temperature, low-density,low salinity H2O-CO2-NaCl in the main mineralization stage. Gold deposits in Jinniushan area arelocated in the steeply dipping extensional faults of the early stage, belongs to polymetallic sulfide quartzvein type. The ore-controlling structures were relatively open, and not easy to concentrate ore fluids, sothe ore-scale was small. The metallogenic belt was missing tectonic conditions for Jiaojia style golddeposit. Study on newly discovered Chakuang gold-antimony deposit showed that the deposit is amid-low temperature hydrothermal type deposit, which belongs to epizonal orogenic gold deposit, andthe mineralization age is consistent with other orogenic gold deposits. As the deposit has been lessaffected by erosion, preserved well, deep prospecting should have a good potential. On this base, itestablished crust continuous mineralization mode of the type of gold deposits.Research indicated that gold deposits in the northeast margin of Jiaolai basin are meso-epithermaltype deposits controlled by Queshan metamorphic core complex, the mineralization of which wasrelated with strong mantle convection and mantle fluids rising in late Yanshanian, the same period withorogenic gold deposits. Pengjiakuang, Songjiagou and Guocheng style gold deposits are the same typedeveloped on a different part of the unified structure system. The newly discovered lead-zincmineralization was post-storeyed, roughly developed in the early late Cretaceous, substantially the same period with Dujiaya gold deposit. The meso-epithermal type lead-zinc-silver-copper-gold polymetallicmineralization in this period in Jiaodong area is widespread.Finally, the paper summarized the mineralization regularity of precious and non-ferrous metaldeposits in Jiaodong area in the Mesozoic, which consist of2stages of precious metals metallogenisisand4stages of non-ferrous metals metallogenisis. The former were orogenic gold mineralization withthe age of125~115Ma, supplemented by Carlin-type gold mineralization; while the later weredominated by3stages of porphyry deposits mineralization occurring at160~155Ma,135~125Ma and115~110Ma respectively, and supplemented by epithermal vein type beryllium mineralization with theage of about205Ma.The paper re-divided the metallogenic belts in Jiaodong area into seven precious and non-ferrousmetals belts, namely the Western Laizhou, Zhaoyuan-Pingdu, Qixia-Penglai-Fushan, NortheasternMargin of Jiaolai Basin, Mouping-Rushan, Wendeng-Weihai and Rongcheng; and divided allmineralization in the Mesozoic into2metallogenic series of gold and polymetals,5sub-series and15deposit types.