Discussion on the Relationships Between Planation Surface and Preservation of Porphyry Copper Deposits in the Zhongdian Region,Yunnan Province,SW China:Constraints from Geomorphic Factor Analysis
Received date: 2020-10-10
Revised date: 2021-04-26
Online published: 2021-07-14
The planation surface formation and its distribution have the characteristics of long-time span and wide distribution range, which is the basic content of geomorphology research.In order to discuss the relationship between the preservation of porphyry copper deposits after mineralization and the planation surface, based on geographic information system(GIS)platform,the paper extracted various geomorphic factors,such as the elevation,the slope and swath profile from digital elevation model(DEM)data,and then the elevation and distribution range of the planation surface were defined in the Zhongdian region.The Zhongdian region is located at the southeastern Tibetan Plateau.In this paper,DEM data from National Aeronautics and Space Administration(NASA) were used to calculate the slope value of 0°~61° in Zhongdian region by GIS technology platform,and the areas with low slope value(0°~10°)were reclassified.Meanwhile,the profile elevation of the Zhongdian region is accurately depicted by using the strip profile,and then the elevation values of the planation surface (+4 100~+4 400 m and +3 100~+3 300 m) and the topographic relief were visually displayed,indicating the distribution height of the planation surface in Zhongdian region.In this study,the thermal history of the typical porphyry(such as Xuejiping complex)was simulated,and the cooling and denudation history of the complex were reconstructed,and the cooling curve were obtained.The results show that the slope distribution in Zhongdian region was concentrated in two planation surfaces between 0° and 10°,revealing the characteristics of the high elevation and low topography.The Xuejiping complex experienced a prolonged slow cooling from the Upper Cretaceous to Late Miocene(<1 ℃/Ma),and the denudation extremely low(500~950 m),reflecting the tectonic quiet period.The process suggests that the planation surface was formed earlier than Late Cretaceous and finally in the Miocene.Combined with the former research results,the widely distributed planation surface in Zhongdian area provides favorable paleogeomorphologic conditions for the preservation of Late Triassic porphyry deposits.As the same time,the cooling history of porphyry deposits also describes the formation process of planation surface,and there is a certain coupling relationship.The existence of planation surface in Zhongdian region not only directly provides geomorphological evidence of surface uplift,but also further supports the stepwise uplift geodynamic model of the southeastern Tibetan Plateau.
Jingjing ZHANG , Chengbiao LENG . Discussion on the Relationships Between Planation Surface and Preservation of Porphyry Copper Deposits in the Zhongdian Region,Yunnan Province,SW China:Constraints from Geomorphic Factor Analysis[J]. Gold Science and Technology, 2021 , 29(3) : 334 -344 . DOI: 10.11872/j.issn.1005-2518.2021.03.180
南非矿业生产大幅回升
据Mining Weekly报道,继3月份同比增长22.5%之后,4月份南非矿业生产飙升116.5%。对增长贡献最大的为铂族金属(PGM),同比增长276%;其次是黄金,增幅为177%;锰矿石,增幅为208%;铁矿石增幅为149%。
金融服务商南非第一国民银行(FNB)认为,4月份飙升不意外,主要是因为2020年第二季度因为封锁导致底数较低。因此,5月份也可能出现2位数的同比增幅。尽管4月份增长强劲,但按照官方GDP计算方法,经过季度调整的4月份环比增幅只有0.3%,而1月份到3月份的平均月度增幅为3.2%。一季度强劲增长表现在该行业的真实GDP,经年化后的季度环比增幅为18.1%,为真实GDP增幅贡献了1.2个百分点。矿业生产持续月度增长对于第二季度GDP增长非常关键,FNB表示。该行对于矿业的短期前景保持乐观。预计矿业活动仍然得到矿产品价格上涨以及南非主要贸易伙伴经济强劲增长的支持。
莱利银行(Nedbank)赞同进行常规同比分析没有什么意义,而是重点放在讨论经季节调整后的月度环比变化以及前年的数字上。4月份0.3%的月度环比增长主要受到PGM驱动,其增幅为6.8%;锰增长5.9%,煤炭增长4.6%。但是,铜、铬和金产量较上个报告期分别下降了49.6%、10.9%和9.6%。3年平均数据显示,4月份总生产水平上升了4.9%。莱利银行称,4月份矿产品销售呈上升趋势,继3月份的17.2%后环比增幅3.2%。销售也得益于全球需求增长、商品价格强劲以及主要港口经营改善。从3年平均来看,销售额意外上升100.8%,主要受到铂族金属和铁矿石推动,其销售额分别增长334%和135%。与之对比的是,铬铁矿和锰矿石销售额下降。莱利银行称,尽管有统计基数低的因素,但在全球需求增长的推动下,4月份矿业表现良好。
展望未来,矿业发展面临不利因素。从国际上看,工业活动改善和商品价格上涨对采矿业构成支撑;但从南非国内看,用电限制和立法体系不确定带来的下行风险迫在眉睫。另外,该行提示,Covid-19疫情恶化及其带来的对经济的限制措施对复苏步伐仍是威胁。
http://www.goldsci.ac.cn/article/2021/1005-2518/1005-2518-2021-29-3-334.shtml
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