山东玲珑金矿的成矿流体特征

Characteristics of ore forming fluid in Linglong Gold Mine, Shandong, China

山东省玲珑地区是中国最大的金矿区之一。玲珑花岗岩位于山东东部的前寒武纪地盾上，其中产有约几十个金矿和矿化点。这个地区的基底由一套太古宙麻粒岩和斜长角闪岩组成。玲珑花岗岩为片麻状黑云母花岗岩。其南缘是走向ＮＥ、倾向ＳＥ 的破头青韧性剪切带。剪切带长数十千米， 宽３００～８００ ｍ ， 且在其左边衍生出呈雁行状排列的次一级脆韧性构造。这些断裂与剪切带有关，且为控矿断裂。金矿床分为东山、西山两个部分，各具有明显不同的特征。东山为受剪切带控制的网脉型（或蚀变岩型） ，西山则主要是产于脆韧性剪切带中的石英大脉型。其矿化可分为４ 个阶段：（１） 乳白色石英黄铁矿阶段；（２） 含金石英黄铁矿阶段；（３） 含金多金属硫化物石英阶段；（４） 碳酸盐阶段。矿石矿物为自然金及与黄铁矿和黄铜矿相关的银金矿。相关的蚀变主要有硅化、钾长石化、绢云母化及绿泥石化。这些蚀变都叠加在花岗质岩石的矿物组合之上。在玲珑金矿中发现了４ 种类型的包裹体：水溶液包裹体、Ｈ２ ＯＣＯ２ 包裹体、ＣＯ２Ｈ２ ＯＣＨ４ 包裹体和少量富ＣＯ２ 包裹体。其均一温度为１００～３８０ ℃，盐度（ ｗＮａＣｌ） 为４％ ～１９％ ，ＣＯ２ 、ＣＨ４ 有一定含量。δ３４Ｓ、δＤ?

The Linglong area, located in Shandong Province, is one of the largest gold mining camps in China The Linglong granites, hosting about one hundred gold mines and showings are located in the Eastern Shandong Precambrian Shield The area is composed of Archean granulites and plagioclase horblendites forming a complex east west trending anticlinorium The Linglong intrusive is gneissic biotite granite The northeast trending, southeast dipping Puotouqing ductile shear zone occurs in the SE margin of Linglong granite Faults are several kilometers long and 300～800 m wide These faults are related to shear zone and controlled mineralization emplacement The deposit is divided into east and west zone, with a great difference in characteristics The east deposit consists of fault controlled stockwork type veins (or altered type), whereas the west deposit is mainly composed of large veins enclosed within shear zone and faults Four mineralization stages have been recognized: (1)milky quartz pyrite, (2) gold quartz pyrite, (3) gold polymetallic sulfides quartz and (4) carbonate stage The ore minerals are native gold and electrum associated with pyrite and chalcopyrite Associated alteration are mainly silicification, K feldspathization, sericitisation and chloritization These alternations are superimposed on the mineral assemblage of the granitic rocks A combination of H2O rich (with 3%～17% equivalent NaCl), CO2 rich, CO2 H2O, CO2 CH4 and daughter mineral bearing inclusions present in the four stages of vein formation indicates an evolutionary trend for the ore mineralizing fluid Two dominant phases are apparent, a NaCl H2O system and a CO2 H2O CH4 system, with a homogenization temperature ranging from 200 ℃ to 380 ℃ This may best be explained as unmixing of the two systems from a single phase However, a few oxygen and hydrogen isotope analyses of fluids from stage I, II, and Ⅲ of veins indicate a meteoric water (+2‰) mixing, driving the composition towards negative oxygen values (-2‰) The occurrence of a CO2 dominated system could be interpreted as having stemmed from a deeper fluid of magmatic or metamorphic origin