新疆萨热克铜矿床绿泥石化蚀变相与构造-岩浆-古地热事件的热通量恢复

Chloritization Facies and Restoration of Heat Flux for Tectonic-Magmatic-Thermal Events of Sareke Copper Mine in the Xinjiang Uygur Autonomous Region, China

据新疆萨热克铜矿区内绿泥石化蚀变相的产状可划分为A型、B型、C型和D型4期。采用绿泥石矿物温度计和地球化学岩相学研究,认为4种绿泥石蚀变相为陆内红层盆地中紫红色铁质碎屑岩系发生褪色化蚀变机制之一。A型和B型绿泥石相为中-晚侏罗世—早白垩世构造-热事件所形成,A型自生粒间状绿泥石在侏罗系-下白垩统中总体顺层分布,形成温度在163~217℃,与辉铜矿共生且形成于埋藏-压实成岩期,热流密度为40.39~48.43 Jm-2s-1,热通量较小。B型微细脉型绿泥石化蚀变相形成于盆地流体改造期,总体沿切层裂隙和显微裂隙分布,与辉铜矿和斑铜矿等共生,形成温度为188~219℃,热流密度较大,在116.90~330.49 Jm-2s-1。斑铜矿+辉铜矿型(196~237℃)和斑铜矿型(203~226℃)铜矿石带指示了盆地流体改造富集成矿的中心部位,热流密度在330.49~878.78 Jm-2s-1,其热流密度明显较大。B型绿泥石相与碎裂岩化相和沥青化蚀变相具有多重耦合结构,形成温度越高,裂隙渗透率越高,可达30×10-6 cm2/211~227℃,推测存在热启裂隙作用。C型和D型绿泥石相为构造-岩浆-热事件所形成,C型团斑状-细脉状绿泥石化蚀变相分布在辉绿辉长岩脉群边部和外接触带含铜漂白-褪色化蚀变带中,含铜蚀变辉绿岩发生绿泥石化相蚀变温度为平均为175℃,平均热流密度321.46 Jm-2s-1,在克孜勒苏群褪色化杂砾岩中其绿泥石形成温度较高(236~238℃),热流密度高达442.86~922.63 Jm-2s-1;而D型绿泥石化蚀变相分布在碎裂岩化蚀变辉绿辉长岩脉群中,揭示遭受构造热事件的古地温在121~185℃,平均热流密度为239.59 Jm-2s-1。四种类型绿泥石蚀变相揭示萨热克铜矿区经历了异常古地场演化和古热事件。

Chloritization is predominated in Sareka-type copper deposit. According to occurrences of chloritizations, they may be classified into A-, B-, C- and D-types of chloritization facies. Based on the study of mineral thermometer of chlorite and chlorite geochemical facies, it might have been that four different kinds of chloritization facies were one of the main factors for discolored alterations in Sarekebayi Jurassic to Lower Cretaceous continental red-bed basin, and it was closely related to copper accumulations and mineralization for Sareke glutenite-type copper deposit. A-type and B-type chloritization facies may form with tectonic-thermal events, for A-type chloritization facies, exhibited among the mineral grains and intergrowth with chalcocite, exist along Jurassic and lower Cretaceous strata. The A-type may form at 163-217 ℃ with low heat flux at 40.39-48.43 jm-2s-1, which cloud be produced by the tectonic-thermal event during the buried-compaction diagenesis stage. However, B-type chloritization facies with micro-veins, filled up along cross-layer fractures and micro-fractures, may be generated during the reworking-enrichment mineralization stage of the basin-fluid. The B-type intergrowth with chalcocite and bomite may be produced at 188-219 ℃ in higher thermal flux, i.e., 116.90-330.49 Jm-2s-1. It is assumed that bornite-chalcocite ore zone formed at 196-237 ℃ and bornite ore zone formed at 203-226℃, B-type with the highest heat flux at 330.49~878.78 Jm-2s-1, indicates the center part of reworking-enrichment mineralization of the basin-fluid in Sareke copper mine. B-type chloritization facies had multiple coupled with cataclastic lithofacies and bituminization alteration facies,whereas the higher the formation temperature is, the higher the permeability of fracture up to 30× 10-6 cm2/211-227 ℃ will be, for the coupling relationship between the B-type chloritization facies and permeability of fracture. C-type and D-type chloritization facies may form with Paleogene tectonic-magamtic-thermal event, for C-type chloritization facies exhibiting block-spot and micro-vein existing in the margins of diabase-gabbro dykes and copper-beating bleaching and discoloring altered zone. C-type chloritization facies in copper-bearing altered diabase dyke was produced at 175 ℃ and in the heat flux of 321.46 jm-2s-1 averagely, while C-type chloritization facies from discoloring glutenite of the Kezilesu Formation formed at the temperature ranging from 236 ℃ to 238 ℃ and in the heat flux ranging 442.86 to 922.63 jm2s-1. Finally, D-type chloritization facies disseminated in cataclastic altered diabase dyke, designated for the pale-thermal event of the diabase dyke, had altered and deformed. D-type chloritization facies may form at the temperature ranging from 121 ℃ to 185℃ with the average heat flux of 239.59 Jm-2s-1.