Conservation of geosites as a tool to protect geoheritage: the inventory of Ceará Central Domain, Borborema Province - NE/Brazil

MOURA, PÂMELLA; GARCIA, MARIA DA GLÓRIA M.; BRILHA, JOSÉ B.; AMARAL, WAGNER S.

doi:10.1590/0001-3765201720170600

PÂMELLA MOURA

Programa de Pós-Graduação em Geologia, Departamento de Geologia, Universidade Federal do Ceará, Campus do Pici, Bloco 912/913, 60440-554 Fortaleza, CE, Brazil

Núcleo de Apoio à Pesquisa em Patrimônio Geológico e Geoturismo (GeoHereditas), Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, Cidade Universitária, 05508-080 São Paulo, SP, Brazil

MARIA DA GLÓRIA M. GARCIA

Programa de Pós-Graduação em Geologia, Departamento de Geologia, Universidade Federal do Ceará, Campus do Pici, Bloco 912/913, 60440-554 Fortaleza, CE, Brazil

Núcleo de Apoio à Pesquisa em Patrimônio Geológico e Geoturismo (GeoHereditas), Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, Cidade Universitária, 05508-080 São Paulo, SP, Brazil

JOSÉ B. BRILHA

Departamento de Ciências da Terra, Universidade do Minho, Campus de Gualtar, 4710-057, Braga, Portugal

WAGNER S. AMARAL

Programa de Pós-Graduação em Geologia, Departamento de Geologia, Universidade Federal do Ceará, Campus do Pici, Bloco 912/913, 60440-554 Fortaleza, CE, Brazil

Instituto de Geociências, Universidade Estadual de Campinas, Rua Carlos Gomes, 250, Cidade Universitária, 13083-870 Campinas, SP, Brazil

Correspondence to: Pâmella Moura E-mail: pamella_mm@yahoo.com.br

Figure 2 Selected geosites of the geological framework “Shear Zones”: a) Geosite Evidences of Thrusting of Pedra Branca: The best exposure of a low angle tectonics on Archean/Paleoproterozoic basement. Represent characteristic rock association of Pedra Branca Unit with interlayer between orthogneisses, often affected by boudinage amphibolites and mafic schist. The orthogneisses shows NNE-SSW low angle foliation, SSE mineral lineation and top-to NNW movement. b) Geosite Mylonitic Gneiss of Quixadá: This excellent outcrop is located within a quarry and constitutes records of dextral strike slip ductile Senador Pompeu shear zone. The geosite is composed of homogeneous mylonitic grey orthogneiss with strongly deformed mafic xenoliths and high-angle mylonitic foliation. Selected geosites of the geological framework “Mineralization”: c) Geosite Collophanites of Itataia: The geosite occur as a collophanite stockwork filling fractures, faults and carbonate breccias in marbles and calc-silicate rocks. The genesis of ore is marked by various mineralizing stage, which ultimately form the larger phosphate-uranium deposit known in South America. (Source: Veríssimo et al. 2016VERÍSSIMO CUV, SANTOS RV, PARENTE CV, OLIVEIRA CG, CAVALCANTI GAD AND NOGUEIRA NETO JA. 2016. The Itataia phosphate-uranium deposit (Ceará, Brazil): new petrographic, geochemistry and isotope studies. J South Am Earth Sci 70: 115-144.) (Images: César Veríssimo). d) Geosite Skarns of Paraíso: This outcrop constitutes a good exposure of Fe-Cu skarns associated to calc-silicate rocks and Neoproterozoic granites. It represents the first occurrence of metallic mineralization identified as product of the SQMA (Source: Parente et al. 2015PARENTE CV, VERÍSSIMO CUV, BOTELHO NF AND SANTOS TJS. 2015. Depósitos de escarnitos mineralizados em ferro e cobre do Arco Magmático de Santa Quitéria, Ceará, Província Borborema do nordeste do Brasil. Braz J Geol 45(3): 359-382.) (Images: Clóvis V. Parente). Selected geosites of the geological framework “Granitic Rocks”: e) Geosite Serra do Barriga Granite: This Cambrian, 522-Ma poly-intrusive granitic stock, represents the post-orogenic magmatism at the end of Brasiliano-Pan African Cycle. The stock is formed by rocks ranging in composition from sienogranite to monzogranite. f) Geosite Quixeramobim Granite: This Neoproterozoic, 587-Ma intrusive batholith represents the ending of Brasiliano-Pan-African Cycle being its intrusive processes associated to Senador Pompeu and Quixeramobim shear zones. The batholith is formed by rocks ranging in composition from calc-alkaline granodiorites, diorites, granites and quartz-diorite (Source: Almeida et al. 1999ALMEIDA AR, ULBRICH HGJ AND MCREATH I. 1999. O Batólito Quixadá: petrologia e geoquímica. Rev Geol 12: 29-52.). The area chosen as geosite is a porphyritic grey granite with 15 cm K-feldspar phenocrysts. Kinematic indicators suggested dextral movement according to regional shear zone can be easily founded. Selected geosites of the geological framework “Geomorphological Units” : g) Geosite Inselbergs Field of Quixadá: This geosite represents the most relevant inselbergs field of CCD and one the most known of Brazil. It constitutes a singular landform assemblage resulting from interaction between climate and crystalline rocks. The Galinha Choca is the most famous inselberg, being composed of rich- plagioclase porphyritic granite with mafic enclaves, leucocratic granite portions and quartz-feldspar veins. The inselberg field is characterised by taffonis and marginal collapse of joint blocks. h) Geosite Serra Branca Peak: This 1154-metres peak constitutes CCD´s highest point, predominantly composed of K-feldspar granite with small quartz veins associated to SQMA. The geosite represents a residual massif, named Serra das Matas, where highlands with average elevations between 500 and 600 meters can be observed.

Figure 3 Selected geosites of the geological framework “Archean and Paleoproterozoic Terranes”. a) Geosite Madalena Suite: This outcrop constitutes the best exposure of Paleoproterozoic quartz-dioritic batholith (Madalena Suite) dated about 2.15 and 2.30 Ga and represents a relevant plutonic event affecting Paleoproterozoic rocks assemblage (Source: Costa et al. 2015COSTA FG, PALHETA ESM, RODRIGUES JB, GOMES IP AND VASCONCELOS AM. 2015. Geochemistry and U-Pb zircon ages of plutonic rocks from the Algodões granite-greenstone terrane, Tróia Massif, northern Borborema Province, Brazil: Implications for Paleoproterozoic subduction-accretion processes. J South Am Earth Sci 59: 45-68.). The geosite is composed of equigranular hornblende-rich orthogneiss cut by a fine-grained diorite dyke. Mafic enclaves and locally gneissic banding can be observed. b) Geosite Greenstone Sequence of Pedra Branca: This good outcrop represents the greenstone sequence from Troia Massif, one of the most ancient lithotypes of CCD dated about 2.78 Ga. It is composed of metarhyolites interlayered with actinolite-rich mafic schists. Selected geosites of the geological framework “Supracrustal Sequences”: c) Geosite Metasedimentary Megaxenoliths of Juatama: the best exposure of the relationship between intrusive processes of Neoproterozoic batholiths with the hosting metasedimentary rocks. The geosite is composed of partially-migmatised grey gneiss with metasedimentary xenoliths. These xenoliths were often affected by boudinage, although the primary foliation had been preserved. d) Geosite Kyanite-Sillimanite gneiss of Itatira: This road outcrop is a good exposure that records remarkable retrograded processes related to isothermal decompression during Itatira Nappe evolution, around 630-600 Ma. The site is composed of fine-banded gneiss, with top-to E-NE movement (Source: Garcia et al. 2014GARCIA MGM, SANTOS TJS AND AMARAL WS. 2014. Provenance and tectonic setting of neoproterozoic supracrustal rocks from the Ceará Central Domain, Borborema Province (NE Brazil): constraints from geochemistry and detrital zircon ages. Int Geol Rev 56(4): 481-500. ). Selected geosites of the geological framework “Granulites and Retroeclogites”: e) Geosite Garnet-Amphibolite of Lagoa do Mato: The best exposure of eclogite-facies relics in the CCD represents Neoproterozoic high-pressure metamorphism at the eastern border of SQMA. It is composed of garnet-amphibolite boudins (retrograded eclogites) hosted within aluminous paragnaisses. Plagioclase coronas around garnet can be observed in sample hand. f) Geosite Enderbites of Alto Feliz: This outcrop represents a good exposure of granulite-facies rock in the CCD. It represents records of Neoproterozoic high-grade metamorphism between the western border of SQMA and Brasiliano Lineament and is composed of enderbite crosscut by clinopyroxene-garnet amphibolite dyke. Selected geosites of the geological framework “Santa Quitéria Magmatic Arc”: g) Geosite Biotite Diatexite of Santa Quitéria: This geosite is composed of biotite-diatexite related to final phase of SQMA magmatism about 618 Ma, and granodiorite boudins with ca. 890 Ma ages, that suggest an older input for SQMA magmatism (Source: Araújo et al. 2014ARAÚJO CEG, CORDANI UG, WEINBERG RF, BASEI M AS, ARMSTRONG R AND SATO K. 2014. Tracing neoproterozoic subduction in the Borborema Province (NE-Brazil): Clues from U-Pb geochronology and Sr-Nd-Hf-O isotopes on granitoids and migmatites. Lithos 202-203: 167-189.). h) Geosite Quartz-Diorite of Taperuaba: This outcrop constitutes a good exposure of rocks related to SQMA mature arc magmatism at about 648 Ma, characterised by hybrid magmatism with influence of neoproterozoic crustal components (Source: Araújo et al. 2014). This site is composed of partially mylonitic quartz-diorite with mafic enclaves cut by felsic veins and fractures.

Justification for Scientific Value	Litho-stratigraphy units (Cavalcante et al. 2003)
Geomorphological Units (Figure 2)	Number of selected geosites: 5
Represent the CCD landscape, composed of relief elements resulting from differential erosion acting on crystalline rock terranes characterised by spatial predominance of peripheral depression crosscut by both residual massifs and inselbergs. Its evolution is related to the uplift of South American continental platform in response to opening and subsidence forces, which preceded the Atlantic Ocean rifting and marginal isostatic compensation in the Cretaceous (Maia et al. 2010, Peulvast and Sales 2002, Sales and Peulvast 2007). Two factors were preponderant to shape these landforms: the Neoproterozoic structural control and the climate variability (backwearing and etching process). Selected geosites aim to represent the most relevant features of CCD relief, especially by means view points that allow the observation of the landscape.	-
Granitic Rocks (Figure 2)	Number of selected geosites: 5
Comprises a diverse granitic assemblage (granodiorites, sienites, sienogranites, monzonites to monzogranites and granites) associated to the Brasiliano-Pan African Cycle, represented by stocks with diameters of a few dozens of metres to ring complexes and large batholiths covering up to 1000 km², like the Quixeramobim Batholith. These granitoids present ages between ca. 590 and 470 Ma, being Ediacaran the period of major granitic generation in CCD despite has remained active during the Middle Ordovician (Almeida et al. 1999, Castro et al. 2012). High-K calc-alkaline composition and K-feldspar phenocrysts (larger than 10 cm) are remarkable features in these rocks. Selected geosites aim to represent the diversity of these rocks and illustrate differences in terms of composition, texture, structure and ages.	Itaporanga Intrusive Calc-alkaline Suite, Meruoca Intrusive Sub-alkaline to Alkaline Suite, Undifferentiated Granitoids
Shear Zones (Figure 2)	Number of selected geosites: 9
This framework encompasses records of intense Neoproterozoic tectonism easily identified in all CCD, being characterised by two types of structures: 1) NE-SW-oriented, preferably dextral, strike slip ductile shear zones, representing significant part of a huge continental shear zone system resulting from continental collision during the Brasiliano-Pan African Cycle (Arthaud et al. 2008); 2) Low-angle, nappe-related structures resulting from regional compressive tectonics that culminated with thrusting of Ceará Complex supracrustal sequences over Cruzeta Complex lithotypes. Records of both structures occur extensively along the CCD. For these selection just representative outcrops of regional shear zones were considered, either for delimiting CCD or for being essential to understand geological processes present in other geosites.	Transbrasiliano Lineament (Sobral-Pedro II Shear Zone) and Shear Zones: Senador Pompeu, Quixeramobim, Sabonete-Inharé, Umirim and Tauá
Mineralization (Figure 2)	Number of selected geosites: 5
Thermo-tectonic events that outlined CCD geological framework support a diversified number of mineralization types, some of them holding high economic and strategic values. In general, these features resulted from either metamorphism of magmatic rocks or metal-bearing sediments, as well as a hydrothermal metasomatic processes related to the Brasiliano-Pan African Cycle. The main record range from Paleoproterozoic PGE-bearing chromitite and BIFs to Neoproterozoic skarns and phosphate-uranium deposits. Selected geosites aims to represent the main CCD mineralization types, mainly regarding their relationship with the geological evolution and economic relevance.	Complex Cruzeta and Complex Ceará
Granulites and Retroeclogites (Figure 3)	Number of selected geosites: 9
High-grade granulite and retrograded eclogite relics have been found in rocks that surround the Tamboril-Santa Quitéria Intrusive Suite. This discovery has been preponderant to understand the geological evolution of the region, especially regarding oceanic subduction processes associated to nappe stacking in the supracrustal sequences during the Brasiliano-Pan-African Cycle. The retroeclogites occurs as garnet-clinopyroxene amphibolite boudins and its main diagnostic features include thin plagioclase coronas around garnet and clinopyroxene and Na-plagioclase symplectites as pseudomorphs of omphacite. Granulite bodies occur usually both as clinopyroxene-garnet amphibolites or enderbites, with pressure and temperature records above 9 kbar e 870º C, respectively (Amaral et al. 2012, 2015, Ancelmi et al. 2015, Santos et al. 2009, 2015). Its selected geosites aim essentially, their rarity and fragility.	Ceará Complex (Canindé and Independência Units)
Santa Quitéria Magmatic Arc (SQMA) (Figure 3)	Number of selected geosites: 5
Comprehends rocks generated during the major magmatic event in the CCD, which is intrinsically connected to Brasiliano-Pan African Cycle and West Gondwana collage. Comprises about 40 km² from tonalite to granite anatetic-igneous rocks association brought about by numerous magmatic pulses and recognized as magmatic-arc products. Its evolution occurred between ca. 880 and 600 Ma (Araújo et al. 2012, 2014, Fetter et al. 2003). Selected geosites represent the distinct magmatism phases; taking into account geochronological databases available.	Tamboril-Santa Quitéria Intrusive Suíte
Supracrustal Sequences (Figure 3)	Number of selected geosites: 6
These sequences surround the Tamboril-Santa Quitéria Intrusive Suite and comprise various associations of Paleo- to Neoproterozoic terrigenous metasedimentary rocks, mainly metapelites and metapsamites, whose depositional processes are related to the breakup of Rodinia, followed by a development of a magmatic arc (Arthaud et al. 2008). These rocks record low-angle thrusting under medium to high-grade metamorphism during the Brasiliano-Pan African Cycle, resulting in a complex nappe system associated to local shear zones, migmatisation and igneous intrusions (Arthaud et al. 2008). Selected geosites seek to represent the most characteristic lithotypes of each unit of the Ceará Complex.	Ceará Complex (Canindé, Independência and Quixeramobim Unit)
Archean and Paleoproterozoic Terranes (Figure 3)	Number of selected geosites: 8
Represents the CCD basement, composed of Archean gneiss TTG nuclei (Tróia Massif), as well as Paleoproterozoic metavolcano-sedimentary greenstone sequences and mafic/metamafic complexes (Cruzeta Complex) and related to Rodínia paleocontinent (Brito Neves et al. 1999, Fetter et al. 2000). It has been subject of many researches particularly by its mining potential and geochronological features, and represents the oldest lithological group from CCD and one of the oldest from Northeastern Brazil. Its geosites aimed the most representative lithotypes of each lithostratigraphic unit on the basis on the geochronological database available.	Pedra Branca Unit, Mombaça Unit, Cruzeta Complex and its sub-units, Algodões Unit, Choró Unit, and Madalena Suite

Geosites	Coordinates (SIRGAS 2000)	Typological Category	Main Geological Interest	Main References
Archean and Paleoproterozoic Terranes
Madalena Suite (58)	436050E/9462869S	Area	Igneous Petrology	Costa et al. 2015, G Martins (DT), Oral Communication
Pedra Branca Greenstone Sequence (53)	407142E/9399571S	Point/RC	Metamorphism	AH Fetter (DT), Almeida et al. 2007
Tonalitic Gneiss of Estrema (54)	399650E/9398459S	Point	Geochronological	AH Fetter (DT)
Tonalitic Gneiss of Mombaça (50)	432291E/9358537S	Point/RC	Geochronological	AH Fetter (DT)
Micaschist of Choró-Limão Dam (40)	484170E/9465035S	Point	Metamorphism	Martins and Oliveira 2004, Oral Communication
Metagabbro of Cruzeta Complex (55)	410710E/9423134S	Point	Metamorphism	AH Fetter (DT), MH Arthaud (DT)
Tonalitic Gneiss of Pedra Branca (52)	426553E/9392463S	Point/RC	Metamorphism	AH Fetter (DT), Almeida et al. 2007
Mafic dykes of Boa Viagem (33)	422118E/9438792S	Section/RC	Metamorphism	Oral Communication
Supracrustal Sequences
Kyanite-Sillimanite Gneiss of Itatira (63)	428736E/9494692S	Point/RC	Metamorphism	NA Castro (DT), Garcia et al. 2014
Metasedimentary Megaxenoliths of Juatama (47)	495195E/9437893S	Area	Geodinamics	Oral Communication
Garnet Schist of Quixeramobim (48)	465675E/9425266S	Area	Metamorphism	Arthaud et al. 1993, Oral Communication
Casa de Pedra Cave (71)	422050E/9475555S	Area	Karst	Oral Communication
Furna dos Ossos (70)	427746E/9555380S	Area	Karst	Cultural landmark
Deformed Gneiss of Forquilha (20)	364737E/9580610S	Section/RC	Metamorphism	WS Amaral (DT)
Granulites and Retroeclogites
Enderbites of Alto Feliz (66)	329107E/9566993S	Point	Geodinamics	Amaral et al. 2012
Garnet amphibolite of Lagoa do Mato (60)	423153E/9482966S	Point	Geodinamics	Garcia and Arthaud 2004, Oral Communication
Banded Granulites of Apuiarés (68)	477473E/9567377S	Point	Geodinamics	Amaral and Santos 2008, Garcia et al. 2014
High Pressure Sequence of Cabeça de Touro Farm (16)	373011E/9575841S	Point	Geodinamics	Santos et al. 2015
Retroeclogites of Ipueiras Farm (12)	374635E/9595921S	Point	Geodinamics	Amaral et al. 2011, 2015, Ancelmi et al. 2013, Santos et al. 2009, 2015
Garnet-Clinopyroxene Amphibolite of Juazeiro do Norte (17)	371929E/9570581S	Point	Geodinamics	Santos et al. 2015
Kinzigite of Cachoeira dos Loretos (14)	373254E/9580705S	Point	Geodinamics	Amaral et al. 2011, 2015, Ancelmi et al. 2013, Santos et al. 2009, 2015
Enderbites of Cariré (05a)	333976E/9573265S	Point	Geodinamics	Amaral et al. 2012, JA Nogueira Neto (DT)
Garnet amphibolites of Boa Viagem (61)	409773E/9475826S	Point	Geodinamics	Garcia and Arthaud 2004, Oral Communication
Santa Quitéria Magmatic Arc
Biotite Diatexite of Santa Quitéria (24)	388866E/9524241S	Point	Metamorphism	Araújo et al. 2014
Quartz Diorite of Taperuaba (18)	381531E/9560586S	Point	Igneous Petrology	Araújo et al. 2014
Biotite Monzogranite do Camará (02)	429038E/9601659S	Point/RC	Igneous Petrology	Araújo et al. 2014
Hornblende-Biotite Metatexite of Tejuçuoca (03)	441431E/9577900S	Point	Metamorphism	Araújo et al. 2014
Lagoa Caiçara Migmatite (23)	408594E/9528775S	Point	Metamorphism	NA Castro (DT)
Mineralization
Collophanites of Itataia (74)	--	Area	Mineral	Veríssimo et al. 2016
Skarns of Paraíso (27)	--	Point	Mineral	Parente et al. 2015
Banded Iron Formation of Boa Viagem (56)	411091E/9419581S	Area	Mineral	Veríssimo et al. 2009
Chromitites of Tróia (75)	402131E/9386844S	Point	Mineral	F.G Costa (MA)
Gondite of Madalena (59)	436899E/9464335S	Point/RC	Mineral	Almeida et al. 2007, Oral Communication
Granitic Rocks
Biotite Sienogranite of Quintas Ring Complex (65)	400648E/9550596S	Point	Geochronological	Castro et al. 2012
Serra do Barriga Granite (19)	373291E/9587296S	Area	Igneous Petrology	IC Mattos (DT)
Serra do Pajé (10)	372190E/9560780S	View Point	Igneous Petrology	IP Gomes (MT), SS Tavares Jr. (MT)
Quixeramobim Granite (37)	469420E/9423719S	Point	Igneous Petrology	Almeida et al. 1999, JF Nogueira (DT), Oral Communication
Quixadá Granite (38)	501489E/9451768S	Point	Igneous Petrology	Almeida et al. 1999, JF Nogueira (DT), Oral Communication
Shear Zones
Evidences of Thrusting of Pedra Branca (31)	405497E/9399842S	Section/RC	Tectonics	Caby and Arthaud 1986, GMS Hamelak (MT)
Gneiss Mylonitic Gneiss of Quixadá (39)	513960E/9452548S	Area	Tectonics	Oral Communication
Mylonites of Mombaça (51)	433258E/9357114S	Point	Tectonics	Oral Communication
Itatira Nappe (62)	414960E/9492747S	View Point	Tectonics	Caby and Arthaud 1986
Enderbites of Transbrasiliano Lineament (05b)	333976E/9573265S	Point	Tectonics	Amaral et al. 2012, JA Nogueira Neto (DT)
Cataclasite of the Rio Groaíras Fault (22)	374772E/9545892S	Point/RC	Tectonics	Oral Communication
Tectonite of Independência (29)	347021E/9407463S	Point	Tectonics	Neves 1991
Mylonitic Ortogneiss of Umirim (42)	460416E/9593100S	Point	Tectonics	SA Zincone (MT)
Phyllites of Transbrasiliano Lineament (06)	349908E/9595143S	Section	Tectonics	Oral Communication
Geomorphological Units
Serra Branca Peak (72)	374506E/9473058S	Area	Geomorphological	Cultural landmark
Inselberg Fields of Quixadá (46)	492193E/9448880S	Complex Area	Geomorphological	Maia et al. 2015
Inselberg of Pedra do Cruzeiro (45)	498462E/9451025S	Area	Geomorphological	Maia et al. 2015
Inselbergs of Irauçuba (04)	411799E/9586284S	View Point	Geomorphological	Sales and Peulvast 2007
Pedra do Frade (44)	458817E/9590067S	Area	Geomorphological	Cultural landmark

Legal Framework	Geosite	Modality
Brazilian Law for National Historic and Artistic Heritage Protection (Federal Decree-Law n 25/1937)	Casa de Pedra Cave Pajé Range	Archaeological, Ethnographic and Landscape Heritage Register
Brazilian System for Conservation Units - SNUC (Federal Law n 9.985/2000)	Inselberg Fields of Quixadá	Natural Monument (Ceará Decree n 26.805/2002)
Brazilian Law for Natural Underground Cavities Protection (Decree-Law n 99.556/1990 and 6.640/2008)	Furna dos Ossos Casa de Pedra Cave	Speleological Heritage
Brazilian Forest Code (Federal Law n 12.651/2012)	Madalena Suíte	Permanent Protection Areas
	Micaschist of Choró-Limão Dam
	Metasedimentary Megaxenoliths of Juatama
	Garnet Schist of Quixeramobim
	Serra do Barriga Granite
	Itatira Nappe
	Enderbites of Transbrasiliano Lineament
	Serra Branca Peak
	Serra do Pajé
	Pedra do Frade
Tejuçuoca Municipal Law s/n	Furna dos Ossos	Ecological Park
Quixadá Municipal Law n 1903/2003	Inselberg of Pedra do Cruzeiro	Environmental Protected Zone

[1] Correspondence to: Pâmella Moura E-mail: pamella_mm@yahoo.com.br

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Conservation of geosites as a tool to protect geoheritage: the inventory of Ceará Central Domain, Borborema Province - NE/Brazil

ABSTRACT