See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/303201779
Phosphorites
Chapter · January 1978
DOI: 10.1007/3-540-31079-7_156
CITATIONS
READS
0
400
2 authors, including:
Craig R. Glenn
University of Hawaiʻi at Mānoa
89 PUBLICATIONS 2,151 CITATIONS
SEE PROFILE
Some of the authors of this publication are also working on these related projects:
Collaborative Investigation of Hydraulic and Geochemical Connectivity Between Wastewaters and Land-Use and the Oceanic Waters of Kāneʻohe Bay, Oʻahu View project
Deep Ocean Minerals View project
All content following this page was uploaded by Craig R. Glenn on 28 August 2017.
The user has requested enhancement of the downloaded file.
PHOSPHORITES
PHO'SPHORIT€S
Craig R. Glenn and Robert E. Garrison
from
ENCYCLOPEDIAof SEDIMENTSard
SEDXMENTARYROCKS
edited by
Gerard V. Middleton
McMasterUniversity
with AssociateEditors
MICHAEL CHURCH
Universityof BritishColumbia
MARIO CONIGILIO
University of Waterlso
LAWRENCEA. HARDIE
John HopkinsUniversity
FREDERICKJ. LONGSTAFFE
Universityof WesternOntario
KLUWERACADEMIC PUBLISHERS
DORDRECHT/BOSTON/LON
DON
ISPN 1-4020-0872-4
@ 2003 KluwerAcademicPublishers
s19
represe4tsa significant perturbation of the biogeochemical
cycle for phosphorus,questionsdiscussedbelow.
The element phosphorus averages about 70ppb
(-2.3pmoVl) in seawater,is a limiting nutri€nt to biological
productivity on geologicaltimescales,and regulatesthe global
carbon cycle and climate. Becauseof its low abundanceand
becauseit is closely tied to short-lived biological-chemical
cyclesof growth and decay,phosphorushas a relatively brief
residencetime in the ocean,estimatedfor the surfaceoceanby
Mackenzieetal. (1993)as 0.07 yearsbasedon phytoplankton
uptake. The overall oceanicresidencetime for phosphorusis
estimated'to range betweenca. 10,000years and 40,000years
(Delaney, 1998; Colman and Holland, 2000; Guidry et al.,
2000).
Initial interest in phosphoritesstemmedfrom their importanoe as a raw material for the production of fertilizer
phosphate.Along with potassiumand nitrogen, phosphorus
is critical for plant growth; but, whereasK and N are readily
available from severalsources(seawater,evaporite deposits,
the atmosphere),phosphorus can only be obtained in large
quaatitiesfrom phosphoritedeposits.Following the discovery
in the mid-l9th Century of the role of mineral nutrition in
plant metabolism by the German chemist Justusvon Liebig,
phosphoritedepositsbegan to be exploited after more readily
availableP sourcessuchas guano,manur€,and crustredbones
bpcameinadequateto support expandingagricultural systems.
Plrosphoritesare now the main source of fertilizer P, and
rniaing of phosphoritesis a world-wide enterprise,with major
cent€rs of production in the USA, Morocco, and several
couetries in the Middle East. Excluding China, global
produqtion in 2000 was close to 92,200thousandmetric tons
(rFA,200l).
The main mineral in phosphoritesis carbonatefluorapatite
(CFA) or francolite,which accordingto Slansky(1986)has the
with
simplified general formula Calq[@Oa)6-^(CO3)^]F21*,
nunneroussubstitutionsof both cations and anions (Nathan,
1984;Jarvis etal., 1994).The most important ancient deposits
aie marine, granular phosphoritesthat formed in continental
rnargin or epeiric sea settings (Figure P5). Two of the key
questions about this kind of phosphorite concern: (l) phosphogenesis:how do CFA particles initially form in marine
environments?(2) concenffation:howdo suchparticlesbecome
dominantin granularphosphorites?
PHOSPHORITES
lntroduction
Phosphoritesare rocks enriched in phosphorusrelative to
usuallyexpressed
an enhancement
averagecrustalabundances,
in terms of PzOsconcentrations.Whereas the averageP2O5
content of continental crustal rocks is estimatedas 0.23
percent (Ronov and Yaroshevsky,1969) and sedimentary
rocks average0.03-0.16 percent (McKelvey. 1973), rocks
as phosphoriteshave l5-37 percentP2O5
typically designated
(Bentor, 1980).Phosphoritesthus have phosphatecontents
that are 60 to 160timesgreaterthan the crustalaverageand
on the order of 100 to over 1,000 times greaterthan the
averagesfor common sedimentaryrocks. The most contentious issuesconcerningphosphoritescenteron the mechanism
or mechanismsby which this enrichmenthas taken place in
the geologic past and whether formation of phosphorites
Phosphogenesis
Studies in modern environmentsin which CFA forms have
demonstratedthat this mineral commonly precipitatesduriog
early diagenesisin the upper few tens of @ntimeters of
sediment.The most notable of these environments are the
continentalmargins of Peru, Baja California [M€xico], southwest Africa, and easternAustralia. Whereasthe first three of
these are regions of pronounced easternboundary currents,
strong coastal upwelling, prominent oxygenrninimum zones,
and organic-richsedirnentation(1-20 percentorganic carbon),
the easternAustralia margin is an area of low productivity,
oxygen-rich bottom waters, and sedimentslow in organic
matter (<0.5 percent organic carbon). These differenoes
suggestthat CFA may form in different ways, depending
upon the environmental conditions. Studies of Perri r'nargin
with high
sediments,for example,have linked phosphogenesis
organic carbon burial rates and anoxic diagenesis(Burnett,
1977).In this setting,microbial degradationof organic matter
PHOSPHORITES
Tectonic and Oceanographic Settings of Marine Fhosphorites
INSULAR
SEAMOUNT CONTINENTAL MARGIN
PHOSPHORITES PHOSPHORITES PHOSPHORITES
Carbonate lslands,
Convergentand Passive,
Seamounts,Qryots, Fldges
Hateaus, Atolls,
( Redacements associated Upwelling and Non-Upwelling
Atoll Lagoons,Marine Lakes with F+Mn Crusts)
(Mostly Hardgroundsand
(Redacements; Authigenic
Nodules,some ganular Beds)
Precipitat es?)
-9
6nvective
Circulation
4
l-leat
Flow
Mn./AraS. Lysocline_ACD-
-Calcite
Shallow Cratonic Sett ings
Associatedwi th Transgressions
(Mostly ganular, some
Hardgrounds,Nodules)
Cross-Shell
/8
Lysocline-
cr\-
-@D-
EPEIRIC SEA
PHOSPHORITES
Currents
Cross-Slope
Currents
St rucl ural
Traps
Abyss
EXAMPLES:
il/bdern
Palau ls.
Clipperton Atoll (?)
llrdern
Pacilic Seamounts?
(no data)
Modern
P e r u - C hi l e ,N a mi b i a ,
W. India, Bala California,
E. Australia
Modern
Absert
Ancient
South Pacific:
Naru, Ehnaba, Kita
Daito Jima, Makatea,
Line lslands
Ancient
Pacitic Seamounts
QueenslandPlaleau
Ancient
llonterey Fm.,
Phosphoria Fm.(?),
SEUSA
Ancient
lvlany,e.g.see Glennet al., 1994a;
Cook and NlcElhinny,
1979
lndian Ocean:
Aldabra and
Christmas ls.
FigureP5 Tectonicand oceanographic
settingsof marinephosphorites
as derivedfrom studiesof the modernand ancientrecord(afterCtenn
et al., 1994a,reprintedwith permissionof BirkhiuserVerlagAC).
increasesreactivedissolvedphosphate€O;-) in pore waters
to supersaturationlevels with respectto CFA, probably via
transformation from a metastable amorphous precursor
phase(e.g., seeJarvis etal., 1994).Froelich etal. (1983, 1988)
measured pronounced increasesin dissolved phosphate in
pore waters in the uppermostfew centimetersof Peni margin
sediments (an interfacial "P-spike"), directly below which
dissolved F- decreasedrapidly in concert with declining
phosphate concentrations.They interpreted this pattern as
reflecting CFA precipitation, with diffusion of seawaterderived F- acting to limit the zone of phosphogenesis
to very
shallow burial depths. In addition, Glenn et al. (1988)
postulated that CFA precipitation was also confined to the
sediment-waterinterface due to mineral lattice poisoning by
excessivecarbonate ion concentrationswith sedimentdepth.
Although continued increasesin dissolved phosphate are
provided to Peru margin pore waters deeperin the sediment
column (due to progressivebacterial organic matter degradation), the locus of CFA precipitation thus appearsto be most
strongly associatedwith the interfacial phosphatemaxima that
occurscloselyadjacentto the sediment-waterinterface.Similar
interfacial phosphatespikesare also found in associationwith
the formation of Recent phosphorites along the Mexican
contential margin (Jahnke et al., 1983; Schuffert et al., 1994)
and off the eastern coast of Australia (Cook and O'Brien,
1990;Heggieetal., 1990).
To account for the formation of CFA in organic-poor
sedimentson the eastern Australian margin, O'Brien et al.
(1990) outlined a mechanismwhereby iron oxyhydroxides
scavengeF- from seawaterand POi- derived both from
seawater and from organic matter subjected to oxic and
suboxicmicrobialdegradationwithin the top few centimeters
of sediment (Figure P6). When these particles are buried
into the suboxiczone, they dissolve,releasingboth F- and
POi- to pore waters, thus promoting CFA precipita.tion.
Ferrous iron along with any remainingF- and POI* then
diffuses upward into the oxic zone to be reflxed by ferric
oxyhydroxides and become available for further recycling.
This iron redox-Pcycle may also promote the formation of
glauconite which is commonly associatedwith modern and
ancientphosphorites.Froelichet al. (1988)invokeda similar
process to help explain phosphogenesis
in Peni margin
sediments.
Other potentialsourcesfor the buildup of POj- in pore
watersincludedissolutionof fish debris,metabolicactivitiesof
sulfide-oxidizingor other bacteria,and P releaseto solution by
bacteria in responseto redox changes.Microbial microstructures are presentin many CFA grains, and microbesmay
affect elevationof phosphorusconcentrations
in pore waters,
but it has not been convincingly demonstratedthat they are
directly involved in the formation of CFA (seediscussionin
Krajewskietal., 1994).
PHOSPHORITES
521
Marine phosphorites in the stratigraphic record commonly
have two attributes: (1) they are grain-supported, granular
concentrationsof silt-, sand-, and pebble-sizephosphatic
grains; and (2) they occur as stratified sediment bodies that
display evidence for transport and redeposition by bottom
currents. The most common grains are structurelesspeloids,
which are probably mostly authigenic rather than phosphatized biogenic fecal pellets. Other grain types may include
concentrically coated grains, phosphatic intraclasts and
nodules, primary phosphatic bioclasts (inarticulate brachiopods, vertebratebones,teeth, fish scales),and phosphatized
carbonateskeletalgrains.The richestphosphoriteshaveCFA
cements,but granular phosphoritesmay also be cementedby
carbonateor silicaminerals.
Some stratified phosphorites have traction current structures such as cross-bedding(Glenn and Arthur, 1990),others
have characteristicof turbidites and indicate deposition from
gravity flows (Grimm and Fdllmi, 1994),still othersappearto
FigureP5 Schematicof CFAprecipitationin surficialmarinesediments
be tempestitebeds(Trappe,1992).Many phosphoritesoccurin
illustratingphosphorusderivedfrom either the Fe-redoxcycle or
intervalsthat containevidencefor multiple episodes
directlyfrom the microbialbreakdownof organicmatter.LiShtstippled condensed
primary
phosphogenesis,
of
shallow burial, exhumation,and
fluxes.
areasrepresentsolid phases,black arrowsare solid-phase
hydraulic reworking (Fdllmi, 1989,1990;Glenn and Arthur,
White-outlinedblack arrows indicatereactions,white arrowsare
for CFA precipitationmay be derived 1990). Phosphatichardgrounds are common in such condiffusionpathways.Phosphorus
from eitheror both of direct microbialdecompositionof organicmatter densed sections. Depositional and biological amalgamation
(Corg)or from a redox-couplediron oxyhydroxide-phosphorus
may lead to the formation of thick (meter scale)phosphorite
Duringburialand
pumpingmechanism(rightsideof illustration)beds, and it appearsthat post-depositionalburrowing may
of organicmatterutilizesa sequence
mixing,microbialdecomposition
commonly destroy current induced structuresin many massive
of electronacceptorsin order of decreasingthermodynamicadvantage.
and phosphoritebeds.
Oxygen is usedfirst, followed by nitrate(and nitrite),manganeseThe characteristics above lead most workers to accept
and sulfate.in that order (Froelichet a!.,1979).
iron-oxyhydroxides
(1971) notion of a two-stage mechanism (i.e.,
Baturin's
and
POi- to solution,
Degradationof organicmatter libe^rates
disiolution of FeO-OHliberatesFe2*, PO]-, and F- causingelevated primary phosphogenesis followed by reworking) for the
formation of large, granular phosphoritedeposits.However,
of theseions in porewaters.lf sufficientlevelsare
concentrations
and F ionsdiffusing nontransported phosphorites such as hardgrounds are assoattained,POI- reactswith Ca2+, Mg2+,^SO42into the sedimentfrom seawater,and COj- derivedfrom the oxidation ciated with some granular phosphorites, and only in a few
of organic matter,to precipitatea precursorphosphatemineralwhich cases are the primary phosphatic mudrocks, the supposed
to CFA (francolite;seetext). ExcessPOisubsequentlyrecrystallizes
parental sediment for the redeposited phosphatic grains,
may also diffuseupward toward the sediment-waterinterfacewhere it
clearly identifiable in the accompanying sediment layers.
is resorbedby ferric iron oxyhydroxides.lron may diffuseboth
phosphorites
downwardto be fixedas glauconite(e.g.,Clenn, 1990)undersuboxic Moreover, the dominant types of Proterozoic
phosprimary
phosphorite
mudrocks
and
stromatolitic
are
to
the
oxic
and
upwards
as
FeS
under
anoxic
conditions,
or
conditions,
phorites which were clearly not transported (see papers in
the Felayerwhere it is reprecipitatedas FeOOH. In this laterc-ase,
redox cycle providesan effectivemeansof trappingPOj in the
Cook and Shergold,1986a).
sedimentand promotesprecipitationof CFA, especiallyin more
(cf O'Brienet al., l99o).ModifiedafterJarvis
sediments
organic-lean
Verlag.
of Birkhduser
et al., 1994,reprintedwith permission
Classification of sedimentary phosphorite rocks
Most past attempts to classify phosphoriteswere based on
petrologic characteristicssuch as grain types and/or textures
(e.g.,Riggs, 1979;Cook and Shergold,1986b;Slansky,1986).
More recent schemeshave focused on field-basedcharacterTypesof phosphateparticles and
istics such as sedimentary structures and bedding properties.
concentration processes
Among the most useful of theseis the classificationof Follmi
The precipitationof CFA may produce a variety of particle et al. (1991), who recognized three interpretive genetic
types, including peloids, coated grains, laminae, and smali categoriesbased on relative rates of sedimentaccumulation
nodulesdispersedin muds. In this type of sediment,termed and erosion(FigureP7):
"pristine" phosphate by Follmi et al. (1991), the primary
phosphateparticlesappearto be in situ, with no reworkingby (l) Pristine'.phosphateswhich lack any signs of reworking;
this includesphosphatic rocks as well as more concenmechanical or biological processes.For the most part,
trated phosphoritessuch as phosphatizedstromatolites
however, these dispersed forms have whole rock P2O5
and phosphatichardgrounds.
phosphorites.
well
those
of
economic
below
concentrations
Baturin (1971) accountedfor this disparity by proposing a (2) Condensed:phosphatic particles,laminae, and beds which
"highstand" phosphogenesis
alternating
have been concentrated by winnowing and reworking
model of sea level
processes
or bioturbation.
with "lowstand" reworking by currentsto producewinnowed
phosphaticparticlesthat wereentrainedby
phosphoritelayersin Quaternarydepositsfrom the continental (3) Attochtholrozrs:
shelf of southwestAfrica.
and redepositedfrom turbulent or gravity-driven flows.
,
PHOSPHORITES
Stratification
Stratificationin phosphatic_qgdlmeg$
asa function of timi and energY
a
O.
(t.dao
G|.d.re
Gl.
.o4t
4,dO-.t
lhospltggen'esis
.Ooca6,.c.
O-O.O-t
.dttoOoOO.
Accumulationrates> Erosionrates
'PRISTINE"
In-situ phosphaticdiaclasts
Accumulationratesg Erosionrates
In-situphosphaticlamina
'CONDENSED"
\-.-*
Accumulationrates( Erosionrates
.ALLOCHTHONOUS"
of stratification
types(from Follmi et al., 199"1and Clenn et al., 1994a).Reprintedwith the permissionof
FigureP7 Ceneticclassification
SpringerVerlag.
for a substantialproportion of world phosphateproduction.
Examples include the Cretaceous-EoceneTethyan deposits
and the Permian Phosphoria Formation of western North
America.
Kazakov (1937)made one of the flrst attemptsto explain
such depositsby invoking upwelling and inorganic precipitation of apatite from seawater in coastal regions, an idea
subsequentlymodified to include the role of organic degradaThe formation of //phosphorite giants"
tion in shallowly buried sediments,as outlined above. Most
deposits (typically with reserves phosphorite giants were depositedbeneath relatively shallow
Very large pho^sphorites
sreater than l0' metric tons of PrOs) have been termed watersof marginal seasand epeiricplatforms (Figure P5), and
;phosphoritegiants"by Glennand Aithur (1990)and account most seemto correlatein a generalway with elevatedsealevels
Hybrids of these categoriesare common. One example is
that pristine phosphaticgrains may experienceredeposition
followed by multiple episodesof burial, renewedphosphogenesis and phosphatic cementation, and subsequenterosional
exhumation, resulting in a complex and laterally variable
phosphoritecondensedbed.
PHOSPHORITES
and, more specifically, with marine transgressions.The
interrelated factors involved may include (Glenn et al.,
1994a): (l) highstands of sea level increase the potential
surfacearea for phosphorite accumulationon shelvesand in
continental interiors; (2) highstands may also increase the
potential for upwelling into shelf seas;(3) sedimentstarvation
and phosphogenesis
may be favored during transgressionsby
the trapping of diluting siliciclasticsedimentin proximal parts
of depositionalsystems;(4) wave-inducedand other cross-shelf
currents may develop along flooded margins and platforms,
thus aiding in winnowing, reworking, and concentration of
pristine CFA particles. In addition to transgressivephases,
relativefalls in sealevelwould lower wave baseand may aid in
reworking and concentrating such particles, in the manner
proposed by Baturin (1971). The majority of phosphorite
giants are of the condensedor allochthonousvariety (Fiillmi
et al., 1991).
The abundance of modern phosphorites in upwelling
regions has led many workers to postulate similar settings
for ancient phosphorites. Sheldon (1980), for example,
subdivided large phosphorites into those associatedwith
equatorial upwelling (e.g., the CretaceousTethyan deposits)
and those associatedwith mid-latitude boundary currentsand
trade-windupwelling(e.g.,the PhosphoriaFormation).However,the efficiencyof sustainedupwellingwithin large,shallow
epeiric seasfar from the open ocean, the setting for many
phosphorite giants including the Tethyan deposits,has been
questioned.Alternative models include the delivery of fluvialborne P derived from intensively weathered continental
regionsto epeiricplatforms (Glenn and Arthur, 1990).
523
authigenicCFA in detrital-rich continentalmargin sediments,
and adsorption on iron oxidesformed at mid-oceanridgesand
in non-upwelling continental margin sediments (Delaney,
1998).Due to variations in sedimentationrates, phosphorus
accumulationrates are severalorders of magnitudehigher in
upwelling-phosphogenicand detrital continental margin settings than in open ocean sediments(Filippelli,1997). Present
consensusholds that past variations in the phosphoruscycle
wereresponsesto changesin ratesofchemical weathering,sealevel fluctuations, spreadingrates of mid-oceanridges,glaciation, and oceaniccirculation. Compton etal. (2000)postulated
that phosphoritegiants most likely formed during episodesof
marine transgressionthat coincided with increasedchemical
weatheringrates and decreases
in production ofiron oxidesat
mid-oceanridgesand, for the last 25 million years,convincing
showed that major phosphorite accumulations occurred in
near-synchronicitywith proposedperiods of episodicuplift of
the Himalayan-Tibetan Plateau. Elevated sea levels shift
primary biological productivity to enlarged shallow water
settingswhere organic phosphorusis releasedin sedimentsto
form CFA. Subsequent sea level fluctuations make such
sedimentssusceptibleto reworking, generatingphosphorites.
Viewedin this manner,phosphoritesmay be a proxy for times
in which phosphorusinput to the oceanswas greaterthan the
sinks provided by organic carbon and iron-oxide burial.
Phosphorites, condensed sections and
sequence stratigraphy
Condensedsectionsor sequences
representextremelyslow net
sedimentationover long periods of time. Such intervals have
been long recognized as characterized by the following
Episodicity of phosphorite giants and
features: (l) enrichment of well preservedfossils and fossil
the global phosphorus cycle
fragments;(2) faunal mixing, fossilsfrom different paleontoThe distribution of phosphorite giants in the Phanerozoicis logical zones within a single bed; and (3) widespread
episodic, with peaks in abundancein the Early Cambrian, distribution of sedimentswith negligible thicknesses.In
Ordovician, Permian, Late Cretaceous-Eocene,
and Miocene addition, it has becomeincreasinglyrecognizedthat intervals
(Cook and McElhinny, 1979). This has been variously of stratigraphic condensationare also frequently marked by
explained as the consequenceof favorable positions of the occurrenceof authigenicminerals,including phosphorites
continentalmargins visavisupwellingzones,equableclimates, and glauconites.With the advent of "sequencestratigraphy,"
globalcooling,widespreadanoxiain the oceans,paleolatitude, condensedsections have taken on new signiflcanceas an
and other conditions. However, as noted by Glenn et al. integral component in the stratigraphic architecture of
(l994a), none of these mechalisms provides comprehensive sequencescontrolled by fluctuations in relative sea level.
explanationsfor all phosphoritegiants, each of which has its Loutit el al. (1988) and their colleaguesdefine condensed
own particularities.
sectionsin light of sequencestratigraphyas thin marine units
A related question is whether phosphorite giants record of pelagicto hemipelagicsedimentsthat: (l) are characterized
acceleratedP withdrawal from the ocean into continental by very low sedimentationratesthat are areallymost extensive
margin and epicontinentalsediments,or whether they repre- at the time of maximum transgressionand coincidentwith the
sent a combination of unusual and localized geological surfaceof maximum flooding; (2) are associatedwith apparent
circumstances
unrelatedto global controls. Sheldon(1980), marinehiatuses;and (3) occuras omissionsurfacesor marine
for example, postulated that the episodicity of marine hardgrounds. They result from sediment starvation during
phosphorite deposition resulted from variations in global timesof maximum ratesof sealevelrise.Theseoccur along the
deep-oceancirculation. A number of recentstudies,however, ,break separatingtransgressivebnd highstand systemstracts
'
suggest that several phosphorite giants required a net P (Figure P8). Assumingthat seisniicreflectorsreflecttimeJines,
withdrawal rate comparableto that observedin modern Perri sequencecondensationmay, hypothetically, also occur anymargin sediments(c/ Filippelli and Delaney,1992;Glennetal., where that reflectors converge such as, for example, along
1994b;Compton et al., 2000).Thus, if phosphoritegiants of surfacesof onlap, backstepping,downlap and toplap (Kidwell,
the past do indeed record episodicacceleratedP withdrawal, 1991; Figure P8). In addition, while phosphoritesmay be
the presentday must be included among theseepisodes.
generallyassociatedwith transgressivephasesof secondand
The global phosphoruscycle is complex and poorly under- third orders changes of sea level (5-50 and 0.5-5 Ma,
stood. Phosphorusinput to the ocean is mainly from rivers, respectively),much reworking of these may occur during
secondarilyfrom eolian phosphorusparticle transport. Major interveninghigher orders of sealevel change(forth, fifth, and
oceanicsinksincludeorganicmatter, fine-graineddisseminated sixth order; 0.1-0.5,0.01-0.1,and <0.01Ma, respectively).
524
PHOSPHORITES
However,as noted above,most major episodesof phosphorite
associatedwith guano, and some may have precipitated
genesis do appear to be related to transgressive, phases,
in insularmarinelakesor other settings.
although the occurrence of reworked deposits within the (2) Seamountand Guyotphosphoritesand phosphatizedlimeupper portions of highstand systemstracts may also reflect
stones,many associatedwith iron-manganese
encrustaepisodes of condensation and bypassing that occur in v
tions, are commonon elevatedportionsof the seafloorin
association with the convergence of toplapping seismic
all the world's oceans.Although a few are submerged
reflectors (Figure P8). In sum, the actual distribution of
insular deposits,most appearto be of marine origin and
condenseddepositswithin seismicsequences
is probably more
formed in areasof slow sedimentationand a pronounced
complex than depictedby recentmodels.
oxygenminimumzone.Burnettetal. (1987)suggested
they
formed preferentiallyat low latitudes,possiblyin equatorial upwellingregionsof high productivity.They linked the
associationof iron-manganesecrusts to the enhanced
Other types of phosphorite deposits
concentration
of phosphateand metalswithin an oxygen
In addition to phosphoritesformed in continental margin or
minimum zonethat bathesthe upper parts of seamounts.
epeiric sea environments(Figure P5), lesser quantities of
(3) Igneousrocks such as carbonatitesand other alkaline
phosphoritesoccur in three other settings:
igneousintrusivecomplexeswhich are enrichedin fluor(l) Island or insularphosphoritesare commonly composedof
(Slansky,1986).Important economapatite,Ca16(POa)6F2
ic depositsof this kind occur in northern Russia,Brazil,
guano and the replacementproducts of reactionsbetween
and easternand southernAfrica (Cook. 1984r.
bird droppings and the underlying host rock; the latter is
commonly a carbonate, and these types of phosphorites
are important economic resourceson Quatemary carbonate islands in the Pacific and Indian Oceans.The largest Environmental issues connected to phosphorites
depositsof this kind occur on the island of Nauru in the Along with risesin world populationsand living standards,
westernequatorial Pacific (Piper etal., 1990).As noted by exploitation of phosphoritesas a source of fertilizers will
Glenn er al. (1994a), not all island phosphorites are inevitablyalso increase.This may be accompaniedby several
(A)
POTENTIALCONDENSED
PHOSPHORITEDEPOSITSJ;i1
:
:
iiii: Prograding
1i: ;i:.:i.,.iii;f,i:;,llif,i;:;1;
siliciclastics, bioclasts,
and reworked authigenic minerals
TOPLAP
SEQUENCE
BOUNDARY
Highstand
SystemsTracl
Retrograde and down lapped
in-situ authigenic minerals,
"tlood bioclasts". and detrital ouaftz
SEOUENCE
BOUNDARY DOWNLAP
APPARENTTRUNCATION(= BACKLAP)
TransgressiveSystems Tract
(B)
<
HighstandAuthigenicGrains
Reworked Seaward
ti\S$
/'*,
,d..*
TransgressiveAuthigenicGrains
ln Silu or Locally Reworked
SB/TS
FigurePB Potentialrelationships_between
sequencestratigraphy,
(A) Possiblepositionsof sequence
condensedsectionsand phosphorites.
(stipples),
condensation
within an idealizeddepositional
(afterKidwell,i991). (B)Sihematicillustration
sequence
oithe placemeniof nonreworkedpristineauthigenicphosphorite(and/orglauconite)and reworkedphosphorite(and/orglauconite).Pristinephosphitesmayform within
transgressive
systemstractsand at the maximumfloodingsurface,whereaslater phasesare reworkedseawardwithin highstandsystemstracts.
(C)Thetim.ing.
of systems
tractsdevelopmentwith respectto one cycleof sealevelchange.LSTlowstandsystemstract TSi transgressive
systems
tract,HST.hiShstand
systemstract,TS transgressive
surface,MFSmaximumfloodingsurface,SB sequenceboundary.Dotson the sealeveicurve
representfocationsof maximumphosphoriteemplacement.(AfterClenn et al., 199qa,reprintedwith permissionof BirkhduserVerlagAC).
PHOSPHORITES
525
environmentalproblems(seeJarvis etal., 1994),among which
three are especiallysignificant:
is evidencethat phosphorusmay also be deliveredto the sites
of phosphogenesisby a redox cycle whereby phosphorus
(l) Mining and processing:most phosphorites are extracted sorbed to iron oxyhydroxidesis releasedas soluble reactiveP
in suboxic pore waters and thus becomesavailable for solid
from open-pit mines with their attendant problems of
phasefixation into the CFA compound. Very large phosphorand
disposal
of
mine
tailings.
In
landscape disruption
ite deposits,termed "phosphorite giants," occur episodically
addition, beneficiationprocessescommonly producephosthroughout the Phanerozoic during discrete time periods.
phatic "waste clays" which are extremelyfine-grainedand
Most were deposited on oceanic slopes and shelvesand in
have poor settling properties,hencemay need decadesto
epeiric seaways.In addition, phosphatic sedimentsare also
settleand thus requirenumeroussettlingponds covering
found on oceanic islands and atop seamounts,guyots and
large areas.
plateaus.Presentconsensusholds that past variaphosphogypsumis a by-product of the submarine
(2) Phosphogypsarn:
tions in the phosphoruscycle and phosphorite output of the
conversion,using sulfuric acid, of phosphorite ore to oceanswere responsesto a variety of factors including seaphosphoric acid, an intermediate compound in the level
fluctuations, changes in rates of continental chemical
manufacture of phosphatic fertilizers. The amount of weathering,shifts in the paleolatitudesof continental margins
phosphogypsumproduced is substantial. Jarvis et al.
and in positionsofcoastal upwellingzones,and in patternsof
(1994)estimateworldwideannualproductionon the order
oceaniccirculation.
of l00metricMt. Although this form of gypsum has
parts
of the world,
commercial applications in many
Craie R. Glenn and Robert E. Garrison
governmentalregulationsin the USA preventits usage,in
(apparently
part due to an associationwith radionuclides
238Udecaychain, especially
in a separatephase)in the
Bibliography
radon. Stockpiling of this material is thus necessary, Baturin, G.N., 1971. Stagesof phosphorite formation on the ocean
leading in turn to potential problems of air and water
floor, NaturePhysicalSciences,232:6l-62.
contaminationin the vicinity of the stockpiles.
Bentor, Y.K., 1980.Phosphorites-The unsolvedproblems.In Bentor,
Y.K. (ed.), Marine Phosphorites-Geochemistry,
Occurrence,Gen(3) Trace elements: many phosphorites contain small but
esrs.Tulsa: Society Economic Paleontologistsand Mineralogists
significant amounts of potentially toxic elements(e.g.,
Special.
Publicaion, 29, pp. 3-18.
cadmium, selenium,arsenic)or radionuclides,particularly Burnett, W .C., 1977. Geochemistryand origin of phosphoritedeposits
uranium.The possibilitythus existsthat harmful amounts
from off Peru and Chile. GeologicalSocietyof AmericaBulletin, 88:
of theseelementscould be releasedinto the environment
8 I 3-823.
during the processingof phosphoriteore or the application Burnett,W.C., Cullen,D.J., and McMurtry, G.M., 1987.Open-ocean
phosphorites-in a classby themselves?In Teleki, P.G., Dobson,
of fertilizersproduced from phosphorites.
M.R., Mooreland, J.R., and von Stackelberg,U. (eds.), Marine
Minerals. D. Reidel (Kluwer AcademicPress),pp. ll9-134.
Colman, A.S., and Holland, H.D., 2000,The global diageneticflux of
Summary
phosphoruslrom marine sedimentsto the oceans:redox sensitivity
and the control of atmospheric oxygen levels. In Glenn,, C.R.,
that
have
Phosphoritesare unique sedimentary deposits
Pr6v6t-Lucas,L.,'-.Lucas,J. (eds.), Marine Authigenesis:From Mipiqued the interestof academicians
and economicgeologists
crobialtoGlobal.SEPM (Societyfor SedimentaryGeology),Special
phosphorus
content,they are
for decades.Due to their high
Publication, 66, pp. 53-76.
the world's most important economicresourceof elemental Compton, J., Mallinson, D., Glenn, C.R., Fi1ippelli,G., Follmi, K.,
Shields, G., and Zanin, Y., 2000. Variations in the global
phosphorus and thus are an essentialadditive for fertilizers
phosphoruscycle. In Glenn, C.R., Pr€v6t-Lucas,L., and Lucas,
chemicals.The most common phosand phosphate-based
J. (eds.), Marine Authigenesis:From Global to Microbial. SEPM
phosphorites
puncphate-bearingmineral in the majority of
(Society for SedimentaryGeology) Special Publication, 66, pp.
fluorapatite(CFA),
tuating the geologicrecord is _carbonate
which has an abbreviated chemical formula of formula
but actuallyalso containsnumerCal9[(POa)6-"(CO3)*]F2+*,
ous substitutionsof both cations and anions.Field observations plus isotopicand pore water studiesof modern marine
phosphorite occurrencesdemonstratethat most form initially
as "pristine," nonreworkeddepositsduring early diagenesis
within the upper few tens of centimetersbeneaththe seafloor.
Most occur beneathstrong upwelling systemswhich provide a
high delivery rate of phosphorus-bearingsedimentaryorganic
matter to the seafloor;this material is subsequentlybroken
down by microbial degradationprocessesin pore waters.
"upgraded" to what are termed
Many are then in turn
"condensed"or "allochthonous" phosphoritesby processes
suchas sedimentwinnowingand reworking,largelyby bottom
currents.Most ancientexamplesof thesedepositsthus usually
occur as stratifiedgranular phosphoritescontaining admixtures of silt to very large sand-sizedphosphaticgrains, the
most common cements of which are silica or carbonate
minerals. Concretionaryand hardground phosphoritesalso
occurin both modernand ancientdeposits.Additionally,there
a |
2?
Cook, P.J., 1984.Spatial and temporal controls on the formation of
phosphate deposits-areview. In Nriagu, J:O., and Moore, P.B.,
(eds.),Phosphate
Minerals. Springer-Verlag,pp. 242-274.
Cook, P.J., and McElhinny, M.W., 1979.A reevaluationof the spatial
and temporal distribution of phosphatedepositsin the light of
plate tectonics.EconomicGeology,74: 315-330.
Cook, P.J., and Shergold,J.H., (eds.).1986a.PhosphateDepositsofthe
World:VolumeI -Proterozoicand CambrianPhosphorites.
Carnbridge
University Press.
Cook, P.J., and Shergold, J.H., 1986b. Proterozoic and Cambrian
phosphorites-anintroduction.In Cook, P.J.,and Shergold,J.H.,
(eds.), PhosphateDepositsof the World: Volumel-Proterozoic and
CambrianPhosphorites.CambridgeUniversity Press,pp. l-8.
Cook, P.J., and O'Brien, G.W,, 1990.Neogeneto holocenephosphorites of Australia. In Burnett, W.C., and Riggs, S.R., (eds.),Pftosphate Deposits of the World: Volume 3-Neogene to Modern
Phosphorites.
CambridgeUniversity Press,pp. 98-121.
Delaney, M.L., 1998.Phosphorusaccumulationin marine sediments
and the oceanicphosphorus cycle. GlobalBiogeochemical
Cycles,
12: 563-5'72.
Filippelli, G.M., 1997. Controls on phosphorus concentration and
accumulation in oceanic sediments. Marine Geology, 139:
23t-240-
PHOSPHORITES
Filippelli, G.M., and Delaney,M.L., 1992.Similar phosphorusfluxes
Qutawna, A.A., Serjani, A., and Zanin, Y.N., 1994. Phosphorite
geochemistry: state of the art and environmental concerns. Eclogae
in ancient phosphorite deposits and a modern phosphogenic
Geologicae Helvetiae, 87'. 643-700.
environment.Geology,2O:709-712.
Follmi, K.8., 1989. Evolutionof the Mid-CretaceousTiiad. Lecture Kazakov, A.V., 1937. The phosphorite facies and the genesis of
phosphorites. ln Geological Investigations of Agricultural Ores.
Notes in Earth Sciences,23. Berlin: Springer-Verlag.
Tiansactions, Scientific Institute ol' Fertilizers and Insecto-Fungicides.
exampleof the
Fcilkni, K.B:, 1990.Condensationand phosphogenesis:
V o l u m e 1 4 2 .p p . 9 5 - l 1 3 .
Helvetic Mid-Cretaceous(Northern Tethyan Margin). In Notholt,
ResearchandDevelopment- Kidwell, S.M., 1991. Condensed deposits in siliciclastic sequences:
A.J.G., and Jarvis,I. (eds.),Phosphorite
exoected and observed features. In Einsele, G., Ricken, W., and
Geological Society of London, SpecialPublication, 52, pp.237Seilacher, A. (eds.), Cycles and Events in Stratigraphy. Springer252.
Veriag, pp. 682-695.
Follmi, K.B., Garrison,R.E.,and Grimm, K.A., 1991.Stratificationin
phosphaticsediments:illustrationsfrom the Neogeneof California. Krajewski, K.P., Van Cappellen, P., Trichet, J., Kuhn, O., Lucas, J.,
Martin-Algarra, A., Pr6vot, L., Tewari, V.C., Gaspar, L., Knight,
in Einsele;G., Ricken, W., and Seilacher,A. (eds.), Cyclesand
R.I., and Lamboy, M., 1994. Biological processes and apatite
Eventsin Strattgraphy. Springer-Verlag, pp. 492-507.
formation in sedimentary environments. Eclogae GeologicaeHelveFroelich,P.N.,Klinkhamer,G.P.,Bender,M.L., Luetke,N.A., Heath,
tiae,87'.701-745.
G.R., Cullen,D., Dauphin,P., Hammond,D., Hartman,N., and
Mynard, V., 1979.Early oxidation of organic matter in peiagic Loutit, T.S., Hardenbol, J., Vail, P.R., and Baum, G.R., 1988.
Condensed sections: the key to age dating and correlation of
sedimentsof the Eastern Equatorial Atlantic: suboxic diagenesis.
continental margin sequences.In Wilgus, C.K., Hastings, B.S.,
Acta, 43: 1075-1090.
et Cosmochimica
Geochemica
Kendall, C.G.S.C., Posamentier, H.W., Ross, C.A., and Van
Froelich,P.N., Kim, K.H., Jahnke,R., Bumett,W.C., Soutar,A., and
Wagoner, J.C., (eds.), Sea-Level Changes: An Integrated Approach.
Deakin, M., 1983.Pore water fluoride in Peru Continental Margin
Society of Economic Paleontologists and Mineralogists, Special
sediments:uDtake from seawater. Geochimicaet Cosmochimica
Publication, 42, pp. 183-213.
Acta,47: 1605-1612.
Froelich,P.N.,Arthur, M.A., Burnett,W.C., Deakin,M., Hensley,V., Mackenzie, F.T., Ver, L.M., Sabine, C., Lane, M., and Lerman, A.,
1993. C, N, P, S global biochemical cycles and modeling of global
Kaul, L., Kim, K.-H., Roe, K., Soutar,A., and Vathakanon,C.,
change. In Wollast, R., Mackbnzie, F.T., and Chou, L. (eds.), 1n1988. Early diagenesisof organic matter in Peru Continental
teractions of C, N, P and S Biochentical Cycles and Global Change.
Margin sediments:phosphoriteprecipitation. Marine Geology, 8O'.
NATO Asi Series, Series l: Global Environmental Change, 4.
309-343.
Springer-Verlag, pp. l-61.
Glenn, C.R., 1990.Pore water, petrologic and stablecarbon isotopic
data bearing on the origin of modern peru margin phosphorites McKelvey, V.8., 1973. Abundance and distribution of phosphorus in
the lithosphere. In Environmental PhosphorusHandbook. Wiley, pp.
and associatedauthigenic phases.In Burnett, W.C., and Riggs,
I 3-3 l.
Depositsof the World:Volume3-Neogene to
S.R. (eds.),Phosphate
Nathan, Y., 1984. The mineralogy and geochemistry of phosphorites.
CambridgeUniversity Press,pp. !9-_61.,- - ModernPhosphorites.
In Nriagu, J.O., and Moore, P.B. (eds.), Phosphate Minerals.
Glenn, C.R., Arthur, M.A., Yeh, H.-W., and Burnett, W.C., 1988.
Springer-Verlag, pp. 27 5-295.
Carbon isotopiccompositionand lattice-boundcarbonateofPeruO'Brien, G.W., Milnes, A.R., Veeh, H.H., Heggie, D.T., Riggs, S.R.,
Chile margin phosphorites.Marine Geology,8O:.287-307.
Cullen, D.J., Marshall, J.F., and Cook, P.J., 1990. Sedimentation
Glenn, C.R., and Arthur, M.A., 1990. Anatomy and origin of a
giant, Egypt. Sedimentology,
dynamics and redox iron-cycling: controlling lactors for the
Cretaceousphosphorite-greensand
apatite-glauconite association on the East-Australian margin. In
37:.123-154.
Notholt, A.J.G., and Jarvis, I. (eds.), PhosphoriteResearchandDeGlenn,C.R., Follmi, K.8., Riggs,S.R.,Baturin,G.N., Grimm, K.A.,
velopment. Geological Society, Special Publication, 52, pp- 6l-86.
Trappe,J., Abed,A.M., Galli-Olivier,C., Garrison,R.E., Ilyin, A.,
Jehl, C., Rohrlich, V., Sadaqah,R.M., Schidlowski,M., Shelton, Piper, D.2., Loebner, B., and Aharon, P., 1990. Physical and chemical
properties of the phosphate deposit on Nauru, Western Equatorial
R.E., and Siegmund,H., 1994a.Phosphorus and phosphorites:
Pacific Ocean. In Burnett, W.C., and Riggs, S.R., (eds.), Phosphate
sedimentologyand environmentsof formation. EclogaeGeologicae
Deposits of the World: Volume 3-Neogene to Modern Phosphorites.
Helvetiae,87: 747-788.
Cambridge University Press, pp. 177-194.
Glenn,C.R., Arthur, M.A., Resig,J.M., Burnett,W.C., Dean,W.E.,
and Jahnke, R.A., 1994b.Are modern and ancient phosphorites Riggs, S.R., 1979. Petrology of the tertiary phosphorite system of
Florida. Economic Geology, 74: 195-220.
really so different?In lijima, A., Abed, A.M., and Garrison, R.E.,
ofthe Tbrtialy Ronov, A.B., and Yaroshevsky, A.A., 1969. Chemical composition of
(eds.),Siliceous,Phosphatic
and GlauconiticSediments
the Earth's crust. In Hart, P.J. (ed.), The Earth's Crustand Upper
and Mesozoic.Proceedingsof the 29th International Geological
Mantle. American Geophysical Union Geophysical Monograph
Part C. Utrechr VSP BV, pp. 159-188.
Congress,
13, pp. 37-57.
Grimm, K:A., and F61lmi,K.B., 1994.Doomed pioneers:allochthonous crustaceantracemakersin anaerobic basinal strata, Oligo- Schuffleri,J.D., Jahnke, R.A., Kastner, M., Leather, J., Sturz, A., and
Wing, M.R., 1994. Rates of formation of modern phosphorite off
Miocene San Gregorio Formation, Baja California Sur,.Mexico.
West.ern Mexico. Geochemica et Cosmochemica Acta, 58: 5001Palaios,9:313-334.
5010.
Guidry, M.W., Mackenzie,.F.T.,and Arvidson, R.S., 2000-Role of
tectonicsin phosphorusdistribution and cycling. In Glenn, C.R., Sheldon,R.P., 1980.Episodocityof phosphatedepositionand deep
ocean circulation-a hypothesis. In Bentor, Y.K. (ed.), Marine
From
Pr6v6t-Lucas,L., and Lucas, J. (eds.),Marine Authigenesis:
Occurrence,Genesis.Society of EcoPhosphorites-Geochemistry,
Global to Microbial. SEPM (Society for SedimentaryGeology),
nomic Paleontologistsand Mineralogists,SpecialPublication,29,
SpecialPublication,66, pp. 35-51.
pp. 239-247.
Heggie, D.T., Skyring, G.W., O'Brien, D.W., Reimers,C., Herczeg,
Tiptree, Essex:
A., Moriarty, D.J.W., Burnett, W.C., and Milnes, A.R., 1990. Slansky,M., 1986.GeologyofSedimentaryPhosphares.
North Oxford Academic.
Organic carbon cycling and modern phosphoriteformation on the
Trappe, t., 1992. Microfacies zonation and spatial evolution of a
East Australian continental margin: an overview. In Notholt,
iirbonate ramp: marginal Moroccan phosphatesea during the
Development.
Resedrchand
A.J.G., and Jarvis,I. (eds.),Phosphorite
81: 105-126.
paleogene.
Rundschau,
Geologisches
GeologicalSocietySpecialPublication, 52, pp. 87-117.
IFA (International Fertilizer lndustry Association), 2001. Quarterly
PhosphateRock Statistics,January-December2000. A/01/15r, pp.
l-14.
Cross-references
Jahnke,R.A., Emerson,S.R., Roe, K.K., and Burnett,W.C., 1983.
Authigenesis
continental
The present day formation of apatite in Mexican
Acta, 4'l: 259-266. Diagenesis
margin sediments.GeochimicaetCosmochimica
OceanicSediments
Jarvis,L, Bumett, W.C., Nathan, Y., Almbaydin, F., Attia, K.M.,
Castro, L.N., Flicoteaux, R., Hilmy, M.8., Hussain, V., Upwelling
View publication stats