东天山红山高硫型浅成低温铜-金矿床：中生代成矿与新生代氧化的K-Ar、Ar-Ar年代学证据及其古构造和古气候意义

Geochronology evidence of Mesozoic metallogenesis and Cenozoic oxidation at Hongshan HS-epithermal Cu-Au deposit,Kalatage region,eastern Tianshan,and its tectonic and paleoclimatic significances.

红山铜-金矿床位于新疆吐哈盆地南缘大南湖-突苏泉晚古生代岛弧带北段的中生代上叠火山盆地中,产于卡拉塔格铜-金矿带上,是新疆近年新发现的具大型远景的高硫化物型浅成低温热液铜-金矿床。铜-金成矿作用与中生代的火山活动及次火山岩侵入相关。该矿床处于东天山极端干旱荒漠地带,是东天山最炎热的地区之一,最高温度达到60℃,降水量平均只有34.1mm/y。干旱少雨和极大的蒸发作用造成氧化带极其发育,厚达50m～60m,由一系列复杂罕见的硫酸盐矿物组成。通过对红山铜-金矿床中石英闪长岩—黑云母花岗岩—二长花岗岩中角闪石、黑云母的K-Ar年龄测定,其年龄分别为296.5±6.7Ma、232.0±3.5Ma和217.10±6.4Ma,其中黑云母花岗岩的黑云母Ar-Ar年龄为238.0±2.4Ma,相当于晚石炭世末-三叠纪。并且由于含矿火山岩含有花岗岩的角砾,表明与成矿有关的岩浆活动晚于上述花岗岩,应为中生代的产物。区域上,三亚、白石泉花岗岩、红柳构花岗岩年龄以及白山钼矿的辉钼矿Re-Os年龄均为三叠纪,表明东天山地区存在中生代成岩成矿事件。对红山矿区氧化带三种含钾硫酸盐矿物进行了K-Ar年龄测试,结果显示现今地表以下1m的绿钾铁矾K-Ar年龄为56.0±4.0Ma,地表以下1.5m的高铁叶绿矾的K-Ar年龄为8.6±1.1Ma,地表以下10m的绿钾铁矾K-Ar年龄为14.7±1.7Ma,地表以下14m的斜钾铁矾K-Ar年龄为4.1±0.4Ma。因此推测红山矿床氧化带不同硫酸盐矿物的表生年龄分布在60～3.7Ma之间。不同类型矿床的氧化带年龄亦表明氧化带氧化作用主要发生在新生代。所获得的氧化带年龄与印度—亚洲大陆碰撞及随后青藏高原的多期幕式隆升时限具有较好的对应关系,可能是青藏高原碰撞隆升远程效应的表现和记录。同时,本研究初步提出使用不同种类硫酸盐矿物作为气候变化指标的可能,对于新生代以来PETM等事件研究具有借鉴意义。

Located in the Paleozoic uplift along the southern margin of Tu-Ha basin in eastern Xinjiang, the newly discovered Hongshan HS-epithermal to porphyry Cu-Au deposit occurs in the superimposed Mesozoic volcanic basin upon the north section of Late Paleozoic Dananhu-Tousuquan accretionary arc. Hongshan Cu-Au deposit, on the edge of the desert, is one of the driest areas in eastern Tianshan. Moreover, the highest temperature has been up to 60℃, and the average rainfall receives only 34.1mm/y. The light rainfall and rapid evaporation in the vicinity of this deposit have allowed the formation of a great variety of water-soluble sulfates. Oxidization zone of this deposit lies on the upper part of primary sulfide orebodies appearing with a depth of 50m - 60m, which is dominant in sulfate minerals. The Hongshan Cu-Au deposit is controlled by the tectonic, stratum, magma activity and volcanic apparatus, whereas Cu-Au mineralization is closely related to volcanic activity in Mesozoic and sub-volcanic intrusive rocks. K-Ar isotopic ages of biotite and hornblende from the wall rock-quartz diorite, biotite granite and monzonite granite are 296. 5 ± 6. 7Ma, 232. 0 ±3. 5Ma and 217. 10 ±6.41Ma respectively. And Ar-Ar isotopic age of biotite from biotite granite is 238.0±2. 4Ma. The orebearing rhyolitic breccia lava contains breccia of the biotite granite, which indicates the volcanism, and related Cu-Au mineralization occurred later than the granite, possibly in Mesozoic. K-Ar ages of granitoids in Sanya, Baishiquan and Hongliugou area and Molybdenite Re-Os age of Baishan Mo deposit all are in Triassic. Besides Late Paleozoic magmatism, Mesozoic magmatic event was widespread in eastern Tianshan. The K-At age dating indicates that the K-Ar age of Voltaite occurred below surface 1 m is 56. 0± 4. 0Ma, K-Ar age of Ferricopiapite occurred below surface 1.5m is（8.6 ± 1.1 ） Ma, K-Ar age of Yavapaiite occurred below surface 14m is 4. 1±0.4Ma, and K-Ar age of voltaite occurred below surface 10m is （ 14. 3± 1.7） Ma. So the age interval of oxidation zone is between 60 -3.4Ma in Hongshan Cu-Au deposit. Oxidization and weathering occurred at Cenozoic era （from 65Ma） in oxidation zone, which can be identified through comparing with different deposits. The oxidation ages of Hongshan not only coincide with collision of India-Asia and multistage uplifting of Qinhai-Tibet Plateau subsequently, but also is the effect and record of collision and uplifting of Tibet Plateau. The predecessor did much research through biota, isotopes, and susceptibility in PETM event. This paper tries to use different sulfate minerals demonstrating climatic change.