A study of the NW Kakamas Domain in South Africa/Namibia provides a new,unified lithostratigraphy and evolutionary history applicable to the whole Namaqua Sector.The Mesoproterozoic history ranges from～1350 Ma to 960 Ma,but isotopic evidence suggests it was built upon pre-existing Paleoproterozoic continental crust that extended west from the Archaean Craton.In eastern Namaqualand,early rift-related magmatism and sedimentation at～1350 Ma occurred in a confined ocean basin.Subsequent tectonic reversal and subduction at～1 290-1240 Ma led to establishment of the Areachap,Konkiep and Kaaien Domains.In the Kakamas Domain,widespread deposition of pelitic sediments occurred at～1220 Ma(Narries Group).These contain detrital zircons derived from proximal crust with ages between～2020 Ma and 1800 Ma(western Palaeoproterozoic domains)and 1350-1240 Ma(eastern early Namaqua domains),suggesting pre-sedimentation juxtaposition.The pelites underwent granulite grade metamorphism at～1210 Ma(peak conditions:4.5-6 kbar and 770-850℃),associated with voluminous,predominantly S-type granitoid orthogneisses between～1210 Ma and 1190 Ma(Eendoorn and Ham River Suites)and low-angle ductile(D2)deformation which continued until～1 110 Ma,interspersed with periods of sedimentation.This enduring P-T regime is inconsistent with the expected crustal over-thickening associated with the generally-accepted collision-accretion Namaqualand model.Rather,we propose the Namaqua Sector is a'hot orogen'devel-oped in a wide continental back-arc with subduction west of the present-day outcrop.The observed high geotherm resulted from thinned back-arc lithosphere accompanied by an influx of mantle-derived melts.Ductile D2 deformation resulted from"bottom-driven"tectonics and viscous drag within the crust by convective flow in the underlying asthenospheric mantle.This extended tectonothermal regime ceased at～1110 Ma when SW-directed thrusting stacked the Namaqua Domains into their current positions,constrained in the Kakamas Domain by late-to post-tectonic Ⅰ-type granitoids intruded between～1125 Ma and 1100 Ma(Komsberg Suite).The thermal peak then shifted west to the Bushmanland and Aus Domains,where voluminous granites(1080-1025 Ma)were associated with high-T/low-P gran-ulite facies thermal metamorphism and mega-scale open folding(D3).Unroofing of the Namaqua Sector is marked by large-scale,NW-trending,sub-vertical transcurrent dextral shear zones and associated peg-matites and leucogranites at～990 Ma.

P.H.Macey;R.J.Thomas;A.F.M.Kisters;J.F.A.Diener;M.Angombe;S.Doggart;C.A.Groenewald;C.W.Lambert;J.A.Miller;H.Minnaar;H.Smith;H.F.G.Moen;E.Muvangua;A.Nguno;G.Shifotoka;J.Indongo;D.Frei;C.Spencer;P.le Roux;R.A.Armstrong;C.Tinguely

Council for Geoscience,P.O.Box 572,Bellville,South Africa;Department of Geology,University of Stellenbosch,South Africa;Department of Geological Sciences,University of Cape Town,South Africa;Geological Survey of Namibia,Windhoek,Namibia;Department of Geology,University of Free State,South Africa;Department of Earth Sciences,University of the Western Cape,South Africa;The Institute of Geoscience Research,Dept.Applied Geology,Curtin University,Perth,Australia;Department of Geological Sciences and Geological Engineering,Queen's University,Kingston,Canada;Geochronology and Tracers Facility,British Geological Survey,Nottingham NG12 5GG,UK;RSES,Australian National,University,Canberra,ACT,Australia

地学前缘（英文版）

[1]P.H.Macey;R.J.Thomas;A.F.M.Kisters;J.F.A.Diener;M.Angombe;S.Doggart;C.A.Groenewald;C.W.Lambert;J.A.Miller;H.Minnaar;H.Smith;H.F.G.Moen;E.Muvangua;A.Nguno;G.Shifotoka;J.Indongo;D.Frei;C.Spencer;P.le Roux;R.A.Armstrong;C.Tinguely-.A continental back-arc setting for the Namaqua belt:Evidence from the Kakamas Domain)[J].地学前缘（英文版）,2022(04):193-221

Namaqua,Kakamas,Namibia,lithostratigraphy,Archaean,Namaqualand,Areachap,Konkiep,Kaaien,pelitic,Narries,Palaeoproterozoic,pelites,Eendoorn,Suites,Komsberg,Bushmanland,ulite,Unroofing,transcurrent,matites

continental,back,arc,setting,belt,Evidence,from,study,NW,South,Africa,provides,new,unified,evolutionary,history,applicable,whole,Sector,Mesoproterozoic,ranges,Ma,but,isotopic,evidence,suggests,was,built,upon,existing,Paleoproterozoic,that,extended,Craton,In,eastern,early,rift,related,magmatism,sedimentation,occurred,confined,ocean,basin,Subsequent,reversal,subduction,led,establishment,Domains,widespread,deposition,sediments,Group,These,contain,detrital,zircons,derived,proximal,ages,between,western,domains,suggesting,juxtaposition,underwent,granulite,grade,metamorphism,peak,conditions,kbar,associated,voluminous,predominantly,type,orthogneisses,Ham,River,angle,ductile,D2,deformation,which,continued,until,interspersed,periods,This,enduring,regime,inconsistent,expected,crustal,over,thickening,generally,accepted,collision,accretion,model,Rather,propose,hot,orogen,devel,oped,present,day,outcrop,observed,high,geotherm,resulted,thinned,lithosphere,accompanied,by,influx,mantle,melts,Ductile,bottom,driven,tectonics,viscous,drag,within,convective,flow,underlying,asthenospheric,tectonothermal,ceased,when,SW,directed,thrusting,stacked,into,their,positions,constrained,post,granitoids,intruded,shifted,Aus,where,were,facies,mega,scale,open,folding,D3,marked,large,trending,vertical,dextral,shear,zones,peg,leucogranites

0.509717