华北克拉通北缘及邻区印支期岩浆活动与钼和金成矿作用

Indosinian Magamtic Activity and Molybdenum,Gold Mineralization Along the Northern Margin of North China Craton and Adjacent Area

对华北克拉通北缘及邻区19处钼矿床和5处金矿床的产出环境、形成时代和成矿机理及其与印支期侵入岩的关系进行了讨论。尽管各个矿床所处的地理位置不同,但是它们大都在前寒武纪或早古生代地层中产出,并且与印支期侵入岩具有密切的时空分布关系。印支期钼矿床的形成作用可以从早三叠世一直持续到晚三叠世,大规模成矿作用高峰期为230～220Ma。相比之下,金矿床的形成时间明显早于钼矿床,同位素年龄数据集中分布在245～239Ma。研究结果表明,自早三叠世开始,华北克拉通北缘及邻区曾发生过多期大规模伸展构造作用,并且形成若干条近东西向展布的裂陷带。张裂构造作用所诱发的富碱性岩浆作用及相关流体活动为钼或金矿床的形成提供了动力和物质来源,因此,印支期侵入岩发育区是寻找隐伏钼或金矿床的有利地区。

The tectonic setting,ore-forming time,metallogenic mechanism of nineteen molybdenum deposits and four gold deposits and their relationship with the Indosinian intrusions,located along the northern margin of Northern China craton（NCC） and adjacent area,have been discussed.Their geographic sites are different,but most of them occur in Precambrian metamorphic rocks and Early Paleozoic volcano-sedimentary rocks,and show intimate spatial and temporal relations with the Indosinian granitoid intrusions.Although the ore-forming process of molybdenum deposits last from Early to Late Trassic,but the large-scale mineralization event occurs from 230 Ma to 220 Ma.The ore-forming process of the gold deposits occurs prior to the ＂peak time＂ molybdenum mineralization（230 Ma to 220 Ma）.Most of ore-forming age data change from 245 Ma to 239 Ma.Mineralization occurred in Mo and Au deposits locality as dissemination,stockwork,veinlet and vein group as well as replacement along the different fracture zones.Mo deposits can be classified as two types： porphyry and skarn.Au deposits can also be divided into two groups： vein and replacement body.Mineralization was likely formed by filling of ore-bearing fluids or hydrothermal replacement within the reactivated fault or fracture zone.Studies show that the lithospheric and crustal extension prevailed along the northern margin of the NCC following the collision of Xing-Meng amalgamated block and NCC during the period of Latest Permian to Late Trassic period.The post-collisional/post-orogenic extensional activities resulted in the formation of several E-W-trending fault zones,and widespread alkaline or high-K calc-alkaline intrusions.Intensive extension and magmatic activities provide favorable dynamic force and ore-forming material sources for molybdenum and gold mineralization.The identification of Indosinian molybdenum and gold mineralization should encourage renewed mineral exploration aimed at the discovery of blind deposits along the northern margin of the NCC and its adjacent area.The altered and brecciated Indosinian granitoid intrusions may be the favorable exploration targets.