THE INDIAN OCEAN NODULE FIELD: GEOLOGY AND RESOURCE POTENTIAL
CONTENTS 1 THE INDIAN OCEAN NODULE FIELD 1 PHYSIOGRAPHY AND GEOLOGY 2 PHYSICS, CHEMISTRY AND BIOLOGY 3 EVOLUTION OF THE INDIAN OCEAN NODULE FIELD 2 TECTONICS AND GEOMORPHOLOGY 1 RIDGE-NORMAL LINEAMENTS 2 RIDGE PARALLEL LINEATIONS AND ANOMALIES 3 SEAMOUNTS 3 VOLCANICS 1 MAJOR VOLCANICS 2 MINOR VOLCANICS 3 ALTERATION OF VOLCANICS 4 TECTONICS AND VOLCANICS: INTERRELATIONS 4 SEDIMENTS 1 DISTRIBUTION AND SOURCE 2 SEDIMENTARY PROCESSES 5 FERROMANGANESE DEPOSITS 1 NODULE CHARACTERISTICS 2 FACTORS INFLUENCING NODULE FORMATION 3 DYNAMICS OF NODULE FORMATION 4 FERROMANGANESE ENCRUSTATION 5 THE WORLD OCEANS SCENARIO 6 RESOURCE MANAGEMENT 1 RESOURCE IDENTIFICATION 2 MINING TECHNOLOGY 3 ENVIRONMENTAL IMPACT ASSESSMENT 4 METAL EXTRACTION AND PROCESSING 5 LAW OF THE SEA 6 GLOBAL PERSPECTIVES REFERENCES C H A P T E R O N E THE INDIAN OCEAN NODULE FIELD THE INDIAN OCEAN CONSTITUTES ABOUT ONE-SEVENTH OF THE EARTH’S SURFACE AND IS THE WORLD’S THIRD LARGEST WATER BODY THIS OCEAN COVERS AN AREA OF 73 6 MILLION KM2, AND IS SEPARATED FROM THE ATLANTIC AND THE PACIFIC OCEANS BY ROUGHLY 20E AND 147E, RESPECTIVELY (FIG 1 1) THIS OCEAN HAS NO EXTENSION TOWARDS THE NORTH POLE UNLIKE THE ATLANTIC AND THE PACIFIC OCEANS THE DETACHMENT FROM THE ARCTIC POLAR WATER SYSTEM AND THE PRESENCE OF MOUNTAINOUS ASIAN LANDMASS ARE RESPONSIBLE FOR SEVERAL INTERESTING PHENOMENA IN THIS OCEAN, SUCH AS ATYPICAL CIRCULATION OF WATER MASS, EXTENSIVE UPWELLING OF NUTRIENTS ALONG THE EAST AFRICAN COAST AND THE FORMATION OF SUMMER AND WINTER MONSOON IN ASIA, AMONG OTHERS SCIENTIFIC EXPLORATION IN THE INDIAN OCEAN STARTED LONG AFTER THE SAME WAS INITIATED IN THE PACIFIC AND THE ATLANTIC OCEANS HMS CHALLENGER FROM GREAT BRITAIN WAS THE FIRST SHIP TO START RESEARCH IN THIS OCEAN IN A BIG WAY DURING ITS FAMOUS TRANS- WORLD VOYAGES BETWEEN 1872 AND 1876 THE JOHN MURRAY EXPEDITION, ONBOARD MABAHISS IN 1933–1934, WAS THE NEXT MAJOR ONE A FEW OTHER OCEANOGRAPHIC EXPEDITIONS, NAMELY, DANA (1928–1930), SNELLIUS (1929–1930), ALBATROSS (1950– 1952) AND OB (1955–1957), WERE ALSO MADE WITH SPECIFIC OBJECTIVES LATER, TWO MAJOR EVENTS PAVED WAY FOR A FULL-FLEDGED SCIENTIFIC RESEARCH IN THIS OCEAN THESE WERE (1) INTERNATIONAL GEOPHYSICAL YEAR (IGY, 1957–1958) AND (2) INTERNATIONAL INDIAN OCEAN EXPEDITION (IIOE, 1963–1966) THE MAGNITUDE OF IIOE, IN TERMS OF INVOLVEMENT OF SEVERAL COUNTRIES, MADE IT THE GREATEST OCEANOGRAPHIC ENDEAVOUR TO DATE THERE WERE IN ALL 36 SHIPS FROM 13 COUNTRIES, WHICH TOOK PART IN THE EXPEDITION LASTING FOR 4 YEARS AFTER IIOE, THE NEXT MAJOR WORK WAS THE DRILLING OF THE OCEANIC CRUST BY GLOMAR CHALLENGER, UNDER THE DEEP SEA DRILLING PROJECT (DSDP, LATER KNOWN AS THE OCEAN DRILLING PROGRAMME, ODP) THE DRILLING PROGRAMME WAS FURTHER COMPLEMENTED BY THE JOINT OCEANOGRAPHIC INSTITUTIONS FOR DEEP EARTH SAMPLING (JOIDES) AND, IN RECENT TIMES, BY INTEGRATED OCEAN DRILLING PROGRAMME (IODP) IN THE 1980S, THE STUDIES OF THE CARLSBERG AND CENTRAL INDIAN RIDGES STARTED IN AN ORGANISED MANNER THE GERMAN VESSEL FS SONNE DECIPHERED TWO SITES OF SIGNIFICANT HYDROTHERMAL ACTIVITY ALONG THIS RIDGE UNDER AN INDO–GERMAN COLLABORATIVE PROGRAMME, GEMINO THE FRENCH, AMERICAN, BRITISH AND INDIAN EFFORTS ARE PRESENTLY CONCENTRATED ALONG THESE RIDGES IN SEARCH OF HYDROTHERMAL SULPHIDE MINERALISATION AND TO UNDERSTAND THE INTERACTIONS AMONG ASTHENOSPHERE, LITHOSPHERE, HYDROSPHERE, BIOSPHERE AND ATMOSPHERE SOME OF THE IMPORTANT CHARACTERISTICS OF OCEANIC CRUST AND MANTLE ARE FURNISHED IN TABLE 1 1 AMONG THE VARIOUS BASINS IN THE INDIAN OCEAN (FIG 1 1), THE CENTRAL INDIAN OCEAN BASIN (CIOB) WAS PARTICULARLY STUDIED FOR ITS MINERAL POTENTIAL DURING THE LAST TWO DECADES, THE SCIENTIFIC COMMUNITY EXPLORED THE CIOB BOTH EXTENSIVELY AND INTENSIVELY SINCE 1982, MORE THAN 50 CRUISES HAVE BEEN UNDERTAKEN IN THIS BASIN, WHICH ULTIMATELY LED TO THE IDENTIFICATION OF A MANGANESE NODULE-BEARING AREA IN THE CIOB SUCH RESOURCE IS ALSO KNOWN AS POLYMETALLIC NODULES AND FERROMANGANESE 20E GENERAL PHYSIOGRAPHY, ESSENTIAL TECTONIC ELEMENTS AND BATHYMETRY OF THE INDIAN OCEAN AND NEIGHBOURING SEAS (BASE MAP FROM NGDC) THE INDIAN OCEAN NODULE FIELD (IONF) WITHIN THE CENTRAL INDIAN OCEAN BASIN (CIOB) IS SHOWN IN SQUARE BOX NOTE INVERTED Y-SHAPED PROFUSELY FRACTURED MID-OCEAN RIDGE SYSTEM, THE LONG NORTH-SOUTH-TRENDING CHAGOS^LACCADIVE RIDGE AND NINETYEAST RIDGE ON EITHER SIDE OF THE IONF, AND THE ANDAMAN^SUMATRA SUBDUCTION ZONE TOTHE EAST MUKHOPADHYAY, GHOSH AND IYER THE INDIAN OCEAN NODULE FIELD PHYSICAL CHARACTERISTICS OF OCEANIC CRUST AND MANTLE LAYER LITHOLOGY P-WAVE VELOCITY THICKNESS (KM) AVG DENSITY (G/CM3) SOURCES: IYER AND RAY (2003) AND REFERENCES THEREIN THE INDIAN OCEAN NODULE FIELD THE INDIAN OCEAN NODULE FIELD THE REMAINING SOUTHERNMOST PART OF THE IONF (SECTOR D, 13760S–16300S) WAS FORMED AT A SLOW RATE (26 MM/YEAR) AFTER CHRON 23 (I E YOUNGER THAN 50 8 MA) THE STRUCTURAL DETAILS OF THE IONF ARE GIVEN IN CHAPTER 2 A B C D TJT-IN CIR SEIR SWIR INDRANI FZ VISHNU FZ IAPB S 70E THE FOUR SECTORS IN THE INDIAN OCEAN NODULE FIELD (IONF)ÇA TO DÇARE SHOWN IN THE BOX THE OTHER NOTABLE FEATURES ARE CENTRAL INDIAN RIDGE (CIR), SOUTHWEST INDIAN RIDGE (SWIR), SOUTHEAST INDIAN RIDGE (SEIR), CHAGOS^LACCADIVE RIDGE (CLR), INDIAN^AUSTRALIAN PLATE BOUNDARY (IAPB) AND FRACTURES ZONES (INDRANI AND VISHNU) THE CRUST OF THE IONF WAS FORMED BETWEEN 60 AND 45 MA, WITH SECTORS A AND C FORMED AT A FAST RATE, WHILE SECTORS B AND D WERE GENERATED AT A SLOW RATE (SECTOR D, IN FACT, FORMED AFTER THE INDIA^EURASIA COLLISION) DASHED LONG LARGELY NORTH-SOUTH LINES ARE FRACTURE ZONES, AND SMALLER DASHES WITH NUMBERS ARE MAGNETIC ANOMALIES LONG CURVED LINE CONNECTING BLACKDOTS IS THE TRACE OF THE TRIPLE JUNCTION ON THE INDIAN PLATE (TJT-IN) (BASE MAPFROM ROYERETAL 1989) THE FORMATION, EVOLUTION AND MANAGEMENT OF THE MINERAL RESOURCE IN THE IONF AND RELATED ASPECTS ARE TAKEN UP IN THE SUBSEQUENT CHAPTERS HOWEVER, BEFORE THE RESOURCES ARE DISCUSSED, THE SALIENT GEOLOGICAL, PHYSICAL, CHEMICAL AND BIOLOGICAL CHARACTERISTICS OF THE IONF, WHICH HAVE INFLUENCED THE ORIGIN, DISTRIBUTION AND ENRICHMENT OF MANGANESE NODULE DEPOSITS, ARE DESCRIBED HERE 1 PHYSIOGRAPHY AND GEOLOGY PLATE BOUNDARIES OF VARIOUS TYPES IN THE WORLD OCEANS, SUCH AS DIVERGENT, CONVERGENT, TRANSITIONAL AND DIFFUSED, ARE SHOWN IN FIG 1 3 INTERESTINGLY, ALL THESE FOUR TYPES OF PLATE BOUNDARIES CAN BE FOUND IN THE INDIA OCEAN THE MOST SPECTACULAR GEOLOGICAL FEATURES WITHIN AND IN THE NEIGHBOURHOOD OF THE IONF (INCLUDING ITS FLANKS), WHICH HAVE A DIRECT OR INDIRECT BEARING ON THE FORMATION, DISTRIBUTION AND ECONOMICS OF ITS MINERAL RESOURCES, ARE BRIEFLY DESCRIBED MID-PLATE BOUNDARIES: THE IONF IS SANDWICHED BETWEEN TWO PLATE BOUNDARIES— INDIA–AUSTRALIA PLATE BOUNDARY (IAPB) IN THE NORTH AND AUSTRALIA–CAPRICORN PLATE BOUNDARY (ACPB) TO THE SOUTHEAST ASEISMIC RIDGES: THE INFLUENCE OF HOTSPOTS ON THE VOLCANO-TECTONIC FRAMEWORK OF ANY BASIN IN TRANSFERRING ENERGY FLUXES FROM WARMER REGIONS TO THE COLDER REGIONS HAS ALWAYS BEEN OUTSTANDING TWO SUCH PROMINENT ASEISMIC RIDGES RUN ALONG THE WESTERN AND EASTERN BOUNDARIES OF THE IONF THESE RIDGES ARE CHAGOS–LACCADIVE AND NINETYEAST THAT WERE FORMED BY THE ERUPTION OF REUNION AND KERGUELEN HOTSPOTS, RESPECTIVELY MID-OCEANIC RIDGE (MOR) SYSTEM: THE IONF FLOOR IS DISTURBED BY SEVERAL ROBUST, LONG FRACTURE ZONES AND TRANSFORM FAULTS, WHICH APPEAR VERY SIGNIFICANT IN 120 150 180 240 270 300 PLATE BOUNDARIES OF VARIOUS TYPES GREEN ¼ SUBDUCTION ZONES, LIGHT BLUE ¼ MID- OCEANICRIDGE,DEEPBLUE¼DEFORMEDBOUNDARYZONE,RED¼CONTINENTALDEFORMATIONZONE(KREEMER ETAL ,2002) THE INDIAN OCEAN NODULE FIELD