地球多层圈有机—无机相互作用的资源效应

地球内部不同层圈相互作用过程中的物质循环和能量传递对浅层盆地内部多种类型资源的形成及富集具有显著影响。深部地质作用过程与浅部资源效应这一核心科学问题备受关注,其中在深部流体/熔体物质传输影响下的有机—无机相互作用及资源效应是关键所在。梳理了地球多层圈有机—无机相互作用对盆内多种资源的影响机理。在深部流体/熔体活动背景下,有机—无机相互作用主要通过形成利于富有机质烃源岩发育的沉积环境、提供促进生烃的物质能量、产生改造储层性质的流体环境和影响油气组分的聚集效果的方式控制油气资源的形成和聚集;深部流体携带地球深部的气体组分(CH_(4)、H_(2)、CO_(2)等)和热能进入盆地促使了天然氢气和地热资源潜力的形成;深部物质为铀矿提供铀源,富铀流体在生物作用和含烃流体作用下形成砂岩型铀矿;深部流体活动对煤矿资源的形成和变质也产生了较大影响。未来针对地球多层圈有机—无机相互作用的研究应当突破盆地限制,在地球系统的背景下围绕层圈物质和能量传输、盆内与盆外一体化展开。重点对非生物烷烃气成因、工业聚集和天然富(含)氢气藏的成因、富集、潜在勘探区评价、地质储存开展深入研究,助力推进中国能源转型和绿色发展。

A New Discovery of Mineralization as Subseafloor Hydrothermal Replacement in the Duddar Super-Large SEDEX Lead-Zinc Deposit in Pakistan

0 INTRODUCTION Sedimentary exhalative(SEDEX)lead-zinc deposit was traditionally considered as a result of submarine hydrothermal exhalation,including exhalative plume and brine pool models(Izanloo et al.,2022;Spinks et al.,2021;Maghfouri et al.,2020;Sangster,2020,2018;Huang et al.,2019;Rajabi et al.,2015;Goodfellow and Lydon,2007;Large et al.,2005,2001;Peng et al.,2000;Goodfellow et al.,1993;Figures 1a,1b).However,recognition of mineralization as subseafloor hydrothermal replacement in a few SEDEX deposits has challenged the traditional consideration(Magnall et al.,2023,2021,2020a,b;Hayward et al.,2021;Figure 1c).Researchers come to believe that subseafloor replacement rather than submarine exhalation is a dominant process for SEDEX mineralization,but this needs to be examined through more case studies.

Enrichment of Mississippi Valley-type(MVT) deposits in the Tethyan domain linked to organic matter-rich sediments

The Tethyan domain hosts the world's most abundant hydrocarbon and Mississippi Valley-type(MVT) Pb-Zn resources. The relations among organic matter-rich sediments, MVT Pb-Zn mineralization, and the Tethyan tectonic evolution history are an important scientific issue. The data of paleogeographic reconstruction indicate that the Proto-, Paleo-, and NeoTethys oceans mainly lay in low latitude areas between 30°N and 45°S. The high temperature and precipitation and the lack of sea water overturning in stagnant basins resulted in high marine biological productivity and good preservation conditions for organic matter-rich sediments. Consequently, abundant organic matter-rich sediments were developed and preserved in the Tethyan domain and thus created abundant hydrocarbon resources. Mineralization age data demonstrate that MVT deposits mainly formed during the continent-continent convergence in the late stage of the Tethyan tectonic evolution. Deposits are located in the fold-and-thrust belts and forelands of the continent-continent convergence orogen, and spatially associated with hydrocarbon basins. Organic matter-rich sediments are well developed in MVT ore districts, where hydrocarbon activity appeared earlier than or nearly simultaneous with the Pb-Zn mineralization event. Hydrocarbon activity generally began earlier than the Pb-Zn mineralization in individual deposits. Organic matter-rich sediments and hydrocarbons mainly play the role of reducing agents in the MVT Pb-Zn mineralization process. Through bacterial or thermal reduction, dissolved sulfates from sedimentary strata were reduced to generate reduced sulfur for Pb-Zn sulfide mineralization. In summary, the Tethyan oceans have long been in low latitude areas near the equator, making the Tethyan domain develop abundant organic matterrich sediments and associated hydrocarbon resources which reduce sulfates to provide sufficient reduced sulfur for MVT PbZn mineralization in the region.

Palynological constraints on the age of the Mississippi Valley-type Changdong Pb-Zn deposit,Sanjiang belt,West China

Mississippi Valley-type(MVT)Pb-Zn deposits serve as the world’s major supply of Pb-Zn resources.However,the age constraint of MVT Pb-Zn deposits has long been a big challenge,due to the lack of minerals that are unequivocally related to ore deposition and that can be used for radioisotopic dating.Here we show sporopollens can provide useful chronological information on the Changdong MVT Pb-Zn deposit in the Simao basin,Sanjiang belt,West China.The Pb-Zn ores in the Changdong deposit are hosted by internal sediments in paleo-karst caves of meteoric origin.Sphalerite and galena occur as replacements of carbonate minerals and void infillings in the internal sediments.The relations suggest that the Pb-Zn mineralization occurred after the deposition of the internal sediments.A palynological assemblage mainly composed of angiosperm pollen dominated by Castanea,Quercus,and Carya and fern spores dominated by Polypodiaceae,Pteris,and Athyriaceae was identified.These pollen and spores place the ore-hosting internal sediments and the Changdong paleo-karst at early to middle Oligocene.Consequently,the Changdong Pb-Zn deposit must have formed after the early Oligocene(~34 Ma).These age constraints,together with the geological characteristics,indicate that the Changdong Pb-Zn deposit is a paleo-karst-controlled MVT deposit related to fold-thrust systems in the Sanjiang belt.The Changdong deposit is similar to other MVT Pb-Zn deposits in the northern part of the Sanjiang belt,making it possible to extend this Pb-Zn belt 500 km further to the South.Results presented here highlights the potential of sporopollens in dating the age of MVT deposits related to paleo-karst formation in young orogenic belts.